Dichlone

Endpoint summary

Description of key information

The irritating potential of dichlone caused local effects in the stomach such as ulceration, mucosal roughening and wall thickening. In addition, the kidneys were identified as target organs as indicated by increased organ weights with no histopathological correlation in males. The vacuolization of the tubular epithelium observed in a high dose female was also seen in a control group female, therefore this effect is of questionable relevance.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

October 19, 2006 - February 26, 2007

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: Crl:CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hino Breeding Center, Charles River Laboratories, Japan
- Age at study initiation: 9 weeks
- Weight at study initiation: from 327.6 to 363.7 g in the males and from 206.1 to 239.9 g in the females
- Housing: Individually in wire-floored stainless steel cages; during the mating period, 1 male and 1 female were housed together in each cage
- Diet: solid food, MF, lot Nos. 060802, 060907 and 061004, Oriental Yeast Co., Ltd, ad libitum
- Water: ad libitum
- Acclimation period: 8 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22.4 to 24
- Humidity (%): 47.6 to 59.9
- Air changes (per hr): 10 to 15
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

other: sodium carboxymethyl cellulose

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
The test substance was weighed accurately and suspended in 0.5 w/v% CMC-Na solution to prepare 1.0 w/v% solution. 0.1 and 0.01 w/v% solutions were prepared by dilution the 1.0 w/v% solution with 0.5 w/v% CMC-Na solution. These solutions were prepared once every 14 days under a sodium lamp and stored in light-resistant containers in a cool, dark place.

VEHICLE
- Justification for use and choice of vehicle (if other than water): the test substance was insoluble in purified water but a favorable suspension was obtained in an aqueous solution of sodium carboxymethyl cellulose
- Amount of vehicle (if gavage): 5 mL per kg body weight

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

A study to examine the stability of 2,3-dichloro-1,4-naphthoquinone, uniformity, stability and concentration of the preparation solution (Study code X02-0161)” was conducted at Hita Office of the institute. The uniformity of the test substance in the preparation solutions was checked by sampling from the upper, middle and lower layers (n=1 each) of 25.0 and 0.01 w/v% solutions and, after pretreatment, measuring the concentration of the test substance by high-performance liquid chromatography (HPLC). For confirmation of the stability of the test substance in the preparation solutions, the solution used in the uniformity test was stored in a cool, dark place. The samples were collected from the middle layer at the measurement points (8 and 15 days after preparation) (n=1 each) and, after pretreatment, measuring the concentration of the test substance once by high-performance liquid chromatography (HPLC). The concentration of the test substance in the preparation solution was confirmed by sampling from the middle layers of 1.0, 0.1 and 0.01 w/v% solutions immediately after the initial preparation and, after pretreatment, and measuring the concentration once by high-performance liquid chromatography. It was confirmed that 20.0 and 0.01 w/v% solutions were uniform and stable for 14 days in a dark, cool place. It was also confirmed that the concentrations of the test substance in the preparation solutions used in the initial administration were all within 100 ± 10% to the designated values of 1.0, 0.1 and 0.01 w/v%.

Duration of treatment / exposure:

males 42 days, females 41-45 days (until day 4 of lactation)

Frequency of treatment:

daily

Dose / conc.:

0.5 mg/kg bw/day (actual dose received)

Dose / conc.:

5 mg/kg bw/day (actual dose received)

Dose / conc.:

50 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

7 males in control and high dose, 12 males in low and intermediate dose, 12 females in control, low, intermediate and high dose, 5 males and 5 females in control and high dose recovery groups.

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: based on a 14-day range finder
- Post-exposure recovery period in satellite groups: 5 males of the control and the high dose group were examined for reversibility of the effects after 14-day withdrawal of test substance.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
The males were observed twice a day from the first day of administration to the day before dissection and once on the dissection day. The females were observed twice a day from the first day of administration to Day 4 after parturition including the parturition condition and nursing condition and once on Day 5 of parturition (day of dissection). During the recovery period, the animals were observed once every day until the day before dissection.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All males and females were observed once before the start of administration and once a week thereafter (except for the mating period) under blinding and the results were scored. The females were also examined on Day 4 after parturition. The examination from Day 18 of gestation to the day of parturition was not conducted to avoid causing unnecessary stress to female animals.

BODY WEIGHT: Yes
Both the males and females were weighed once a week during the acclimatization period and on the day of group allocation. Thereafter, the males were weighed on Days 1, 3, 7, 14, 21, 28, 35, 42 and 43 (day of taking out, under fasting) of treatment and the females were weighed on Days 1, 3, 7and 14 of treatment, Days 0, 7, 14, 17 and 20 of gestation, and Day 0 (day of parturition), 4 and 5 (day of taking out, under fasting) after parturition. The females in the recovery group were weighed on the same days as males. During the recovery period, both the males and females were weighed on Days 1, 3, 7, 14 and 15 (day of taking out, under fasting) of recovery.

FOOD CONSUMPTION
Food consumption was measured on Days 1, 3, 7, 14, 28, 35 and 42 of treatment for males, and on Days 1, 3, 7 and 14 before gestation, Days 0, 7, 14, 17 and 20 of gestation, and Days 0 (day of parturition) and 4 after parturition for females. Food consumption by the females of the recovery group was measured on Days 1, 3, 7, 14, 21, 28, 35 and 42. During the recovery period, food consumption was measured on Days 1, 3, 7 and 14 of recovery for both males and females. Food consumption was determined in intervals from the measurement day to the next measurement day for both males and females and mean daily food consumption was calculated.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of treatment and at the end of recovery
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes
- How many animals: 5 of the surviving males at each dose level in the ascending order of animal number and for 5 of the females at each dose level in the order of closer date of parturition.
- Parameters examined: Red blood cell count, White blood cell count, Hemoglobin concentration, Hematocrit, Mean corpuscular volume, Mean corpuscular hemoglobin, Mean corpuscular hemoglobin concentration, Platelet count, Reticulocyte ratio, Prothrombin time, Activated partial thromboplastin time, Differential leukocyte count

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of treatment and at the end of recovery
- Animals fasted: Yes
- How many animals: 5 of the surviving males at each dose level in the ascending order of animal number and for 5 of the females at each dose level in the order of closer date of parturition.
- Parameters examined: Aspartate aminotransferase, Alanine aminotransferase, Alkaline phosphatase, Cholinesterase, Gamma-glutamyl transpeptidase, Total cholesterol, Triglyceride, Blood glucose, Total protein, Albumin, A/G ratio, Urea nitrogen, Creatinine, Total bilirubin, Calcium, Inorganic phosphorus, Sodium, Potassium, Chlorine

NEUROBEHAVIOURAL EXAMINATION: Yes
Five males at each dose level in the ascending order of animal numbers were examined for the following items in the final week of administration. Of females expected for parturition, 5 females in each group in the order of closer date of parturition were examined on the day before dissection (Day 4 after parturition) before the start of fasting. No examinations were performed during the recovery period because no abnormalities were noted in the treatment period.
- Battery of functions tested: reactivity / sensory activity / grip strength / motor activity

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
Macroscopic observation including observation of the body surface, openings, subcutaneous, cranial cavity, thoracic cavity, abdominal cavity, pelvic cavity and their contents was performed for all animals at the end of the treatment period (except for the recovery group) and at the end of the recovery period.

HISTOPATHOLOGY: Yes
The trachea, lungs, stomach, intestines (duodenum to rectum including Peyer’s patches), liver, heart, kidneys, bladder, testes, epididymides, prostate, seminal vesicles, ovaries, uterus, vagina, brain (including cerebrum, cerebellum and pons), spinal cord, sciatic nerves, bone marrow (femur), axillary lymph nodes, mesenteric lymph nodes, spleen, thymus, pituitary gland, thyroid gland (including parathyroid) and adrenal glands were examined in 5 males in each group in the ascending order of animal number and 5 females in each of the vehicle control group and 50 mg/kg group in the order of closer date of parturition. The kidneys were examined in all females in the vehicle control recovery group and 50 mg/kg recovery group as well as 5 females in each group in the order of closer date of parturition as abnormality indicative of the effect of the test substance was noted in the females of the 50 mg/kg group. The anterior stomach was examined in the males and females of the vehicle control recovery group, 0.5 and 5 mg/kg groups, and 50 mg/kg recovery group as abnormality suggesting the effect of the test substance administration was found in the 50 mg/kg group at autopsy.
The epididymides were examined in 2 males (Nos. 28 and 29) of the 5 mg/kg group that showed macroscopic lesion, hepatic lymph nodes in 4 males (Nos. 38, 39, 40 and 41) of the 50 mg/kg group and 2 females (Nos. 145 and 146), and glandular stomach in 1 male (No. 45) of the 50 mg/kg recovery group.
In the animal that died (No. 142), stomach, intestines, liver, heart, kidneys, spleen, thymus and adrenal glands were examined to investigate the cause of death.
In 2 dams (Nos. 102 and 149) that showed total litter death, stomach, intestines, liver, heart, kidneys, spleen, thymus and adrenal glands were examined to check the pathological condition and, further, the skin was examined in 1 animal (No. 102).
For 3 females (Nos. 124, 133 and 147) that did not start parturition even after 25 days from confirmation of copulation, the ovaries, uterus and vagina were examined to investigate the cause of infertility.

Other examinations:

In addition, examinations concerning the reproductive and developmental toxicity were performed, for details see chapter 7.8.1

Statistics:

- Body weight (except for the time of taking out), food consumption, hematology, blood biochemistry, organ weight, mean sexual cycle, time to copulation, gestational period, number of corpus lutea verum, number of implantation sites, grip strength, locomotor activity, number of births, number of live births, 0-day sex ratio of live births, 4-days sex ratio of live neonates, body weight of neonates: Bartlett method and, if equal variance was noted at 5% significance level, the one-way analysis of variance was performed. When a significant difference was noted in the analysis of variance, the vehicle control group and each dose group were compared by the Dunnett’s test. If equal variance was not detected, the Kruskal-Wallis rank-sum test was performed to examine the significance in all groups followed by the Dunnett’s multiple comparison test.
- Defecation frequency (number of feces) and urination frequency (number of urine pools): Kruskal-Wallis test and, if a significant difference was noted, Dunnett’s multiple comparison test.
- Copulation rate, fertility rate, conception rate, fertility rate and 0-day sex ratio of live births and 4-days sex ratio of live neonates: chi-square test (by Fisher’s exact test if any of the marginal frequencies was 10 or less).
- Implantation rate, pre-implantation embryo loss rate, post-implantation embryo loss rate of parent animals and delivering rate, birth rate of live births, fertility rate of live births, external appearance abnormality rate, and 4-day survival rate of neonates: Kruskal-Wallis rank sum test for the tested for significance among all groups followed by the Dunnett’s multiple comparison test. The body weights of neonates were analyzed by litter unit and for males and females.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

In the 50 mg/kg group, all the males showed soft feces, 11 showed black soft feces and 4 showed diarrhea. No abnormalities were noted in the 0.5 and 5 mg/kg groups. In the females before establishment of copulation, 9 showed soft feces, 6 showed black soft feces and 6 showed diarrhea in the 50 mg/kg group. During the gestational period, 1 female of the 5 mg/kg group showed pallor, 6 females of the 50 mg/kg group showed soft feces and 4 showed black soft feces. Soft feces, black soft feces and diarrhea were noted in all animals of the 50 mg/kg recovery group. No abnormalities were noted in the 0.5 mg/kg group. One female (No. 142) in the 50 mg/kg group showed soft feces before establishment of copulation and black soft feces in the gestational period and died on Day 23 of gestation.
During the recovery period, two males of the 50 mg/kg recovery group showed soft feces and 3 males showed black soft feces until Day 1 of recovery but the symptoms resolved on the following day and thereafter. Four females of the 50 mg/kg recovery group showed soft feces and 1 female showed black soft feces until Day 1 of recovery but the symptoms resolved on the following day and thereafter.
One female died in the 50 mg/kg group.

Body weight and weight changes:

effects observed, non-treatment-related

Description (incidence and severity):

No significant changes were noted in any of the males of any test substance group. In the females, significantly low body weight was observed in the 5 mg/kg group on Days 17 and 20 of gestation but the changes were not dose-dependent. No significant changes were noted in the 0.5 and 50 mg/kg groups. During the recovery period, no significant changes were noted in any of the males and females in the 50 mg/kg recovery group.

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

No significant changes were noted in any of the males of any test substance group. A significant increase was noted in the females of the 50 mg/kg group on Day 14 of treatment before establishment of copulation. The significant decrease found in the 5 mg/kg group on Day 17 of gestation was not a dose-dependent change. No significant changes were noted in the 0.5mg/kg group. During the recovery period, no significant changes were noted in the males of the 50 mg/kg recovery group. A significant increase was noted in the females of the 50 mg/kg recovery group on Day 7 of recovery.

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

In the males, the white blood cell count increased significantly in the 50 mg/kg group. No significant changes were noted in the 0.5 and 5 mg/kg groups. In the females, the red blood cell count, hemoglobin and hematocrit increased significantly but these were not dose-dependent changes. No significant changes were noted in the 5 and 50 mg/kg groups. At the end of the recovery period, no significant changes were noted in the males of the 50 mg/kg recovery group. In the females, the platelet count increased significantly in the 50 mg/kg recovery group.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

In the males, creatinine levels decreased significantly in the 5 mg/kg group but not dose-dependently. No significant changes were noted in the 0.5 and 50 mg/kg groups. No significant changes were noted in any of the females of any test substance group. At the end of the recovery period, in the males of the 50 mg/kg recovery group, creatinine levels decreased significantly although this decrease was not noted at the end of the treatment period. In the females, no significant changes were noted in the 50 mg/kg recovery group.

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

Two males in the 0.5 mg/kg group showed excessive reaction to pain sensation but the change was not dose-dependent. No abnormalities were noted in the 0.5 and 5 mg/kg groups. No abnormalities were noted in any of the females of any test substance group. As neither the males nor females showed changes suspected of the influence of the test substance administration during the treatment period, the examination was not performed during the recovery period.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

In the males, the relative weight of the kidneys increased significantly in the 5 mg/kg and higher and the absolute weight of the kidneys increased significantly in the 50 mg/kg group. No significant changes were noted in the 0.5 mg/kg group. In the females, significant increases in the absolute and relative kidney weights, and absolute spleen weight in the 50 mg/kg group. No significant changes were noted in the 0.5 and 5 mg/kg groups. At the end of the recovery period, no significant changes were noted in any of the males and females of the 50 mg/kg recovery group.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

The female that died in the 50 mg/kg group showed mucosal depression in the anterior stomach, mucosal blackening in the glandular stomach, discoloration of the kidneys, reduction of the thymus size and swelling of the adrenal glands.
At the end of the treatment period, mucosal depression in the anterior stomach, nodulation of the epididymides, and whitening of the epididymides were found in 1 male of the 5 mg/kg group. In the 50 mg/kg group, border elevation of the anterior stomach was noted in 3 males, mucosal roughening and wall thickening in the anterior stomach in 7, and swollen hepatic lymph nodes in 6. No abnormalities were found in the 0.5 mg/kg group.
In the females, reduction of thymus size was noted in the vehicle control group and in 2 females of the 0.5 mg/kg group. In the 5 mg/kg group, mucosal depression of the anterior stomach was found in 2 females and reduction in thymus size in 1 female. In the 50 mg/kg group, border elevation of the anterior stomach was found in 1 female, mucosal roughening of the anterior stomach in 8 females, wall thickening in 9 females, and swollen hepatic lymph nodes in 3 females. At the end of the recovery period, border elevation of the anterior stomach was found in 1 male of the 50 mg/kg recovery group and mucosal depression of the glandular stomach in another male. No abnormalities were noted in the females of the 50 mg/kg recovery group.

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

The female of the 50 mg/kg group that died showed diffuse hyperplasia of the squamous epithelium and ulcer in the anterior stomach, mucosal necrosis in the fundic area of the glandular stomach, vacuolization of the renal tubular epithelium in the kidneys, atrophy of the spleen and thymus, and localized necrosis of the adrenal cortex.
In the males, localized myocarditis in the heart was found in 1 male, sperm granuloma in the epididymides in another male, and round cell infiltration in the prostate in 2 males in the vehicle control group. In the 5 mg/kg group, ulcer in the anterior stomach was found in 1 male, and sperm granuloma of the epididymides was found in 2 males. In the 50 mg/kg group, cell infiltration in the lamina propria and submucosa of the anterior stomach in 3 animals, diffuse hyperplasia of the squamous epithelium in the anterior stomach in 5 animals, border squamous cell hyperplasia in the anterior stomach in 2 animals, mineral deposition in the jejunal Peyer’s patches in 1 animal, localized myocarditis of the heart in 2 animals, round cell infiltration of the prostate in 1 animal, germinal center development in the hepatic lymph nodes in 4 animals, and ultimobranchial rest in the thyroid gland in 1 animal. No abnormalities were found in the 0.5 mg/kg group. In the females, mineral deposition in the renal papilla was found in 1 female and acceleration of extramedullar hemopoiesis was found in another female in the vehicle control group. In the 0.5 mg/kg group, isolated cysts were found in the kidney cortex of 1 animal. In the 5 mg/kg group, ulcer of the anterior stomach and isolated cysts in the kidney cortex were found in 1 animal, and localized hypertrophy of the renal tubular epithelium was found in another animal. In the 50 mg/kg group, cell infiltration in the lamina propria and submucosa of the anterior stomach in 1 animal, diffuse hyperplasia of the squamous epithelium in the anterior stomach of 5 animals, squamous cell hyperplasia in the border of the anterior stomach in 2 animals, severe vacuolization of the renal tubular epithelium in 2 animals, mineral deposition in the cortico-medullary junction and isolated cysts in the medulla of the kidneys in 1 animal, germinal center development in the hepatic lymph nodes in 2 animals, and ultimobranchial rest in the thyroid gland in 1 animal.
At the end of the recovery period, diffuse hyperplasia of the squamous epithelium in the anterior stomach was found in all animals of the 50 mg/kg recovery group, squamous cell hyperplasia in the border of the anterior stomach in 2 animals, and mucosal necrosis in the fundic gland area of the glandular stomach in 1 animal. In the females, diffuse hyperplasia of the squamous epithelium in the anterior stomach was found in 4 animals of the 50 mg/kg recovery group.

Dose descriptor:

NOAEL

Effect level:

0.5 mg/kg bw (total dose)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: mucosal depression and ulcer in the anterior stomach were observed in the males and females given 5 mg/kg and higher

Critical effects observed:

not specified

Kidney weights

Sex	Group (mg/kg)	Kidney (g/100g)
male	0	0.65
	0.5	0.67
	5	0.72*
	50	0.75**
male recovery	0	0.64
	50	0.68
female	0	0.64
	0.5	0.67
	5	0.67
	50	0.71*
female recovery	0	0.65
	50	0.65

* Significantly different from 0 at P<0.05

** Significantly different from 0 at P<0.01

Histopathological examination of kidneys

Male

Female

mg/kg

0

0 Recovery

0.5

5

50

50 Recovery

0

0 Recovery

0.5

5

50

50 Recovery

ta

ta

ta

ta

ta

ta

ta

ia-pd

ta

ta

ia-nd

ta

ia-nd

ta

ia-nd

ia-pd

fd

Finding

Grade

number of animals

7

5

12

12

7

5

11

1

5

11

1

11

1

9

1

1

1

5

No abnormalities detected

5/5

-

-

-

5/5

-

4/5

0/1

5/5

4/5

-

3/5

-

2/5

-

1/1

0/1

5/5

ballooning of tubular epithelium

+

0/5

-

-

-

0/5

-

0/5

0/1

0/5

0/5

-

0/5

-

2/5

-

0/1

0/1

0/5

Focal hypertrophy of tubular epithelium

+

0/5

-

-

-

0/5

-

0/5

0/1

0/5

0/5

-

1/5

-

0/5

-

0/1

0/1

0/5

Mineralization in cortico-medullary junction

+

0/5

-

-

-

0/5

-

0/5

0/1

0/5

0/5

-

0/5

-

1/5

-

0/1

0/1

0/5

Mineralization in papilla

+

0/5

-

-

-

0/5

-

1/5

0/1

0/5

0/5

-

0/5

-

0/5

-

0/1

0/1

0/5

Solitary cyst in medulla

+

0/5

-

-

-

0/5

-

0/5

0/1

0/5

1/5

-

1/5

-

1/5

-

0/1

0/1

0/5

Vacuolization of tubular epithelium

+

0/5

-

-

-

0/5

-

0/5

1/1

0/5

0/5

-

0/5

-

0/5

-

1/1

1/1

0/5

ta, terminal autopsy;

ia-nd, female animal did not deliver her pups;

ia-pd, dam all her pups were dead;

fd, found dead.

-, not examined

Conclusions:

Based on the findings in this study, the no observed adverse effect level (NOAEL) for the repeated-dose toxicity of dichlone was estimated to be 0.5 mg/kg/day in both males and females.

Executive summary:

A combined repeated-dose oral toxicity and reproductive and developmental toxicity study of 2,3-dichloro-1,4-naphthoquinone was conducted at 0, 0.5, 5 and 50 mg/kg/day using 12 male and 12 female Crl:CD(SD) rats per dose group in accordance with the OECD TG422. The test substance was administered orally in males for 42 days from 2 weeks prior to mating and in females until Day 4 of lactation after parturition to examine repeated-dose toxicity and reproductive toxicity in parent animals and developmental toxicity in offspring. Autopsy was performed for 12 males and 12 females in the 0.5 and 5 mg/kg groups, and for 7 of 12 males and 7 of 12 females in the vehicle control group and the 50 mg/kg group at the end of the treatment period. Five remaining males and 5 females in the satellite group were examined for reversibility of the effects after 14-day withdrawal as the recovery group. The females in the recovery group were not mated in accordance with the test guideline.

Effects of the test substance were noted in the stomach and kidneys. The autopsy results revealed mucosal depression in the anterior stomach in the males and females of the 5 mg/kg group, and border elevation, mucosal roughening and wall thickening in the anterior stomach in the 50 mg/kg group. The histopathological examination showed ulcer in the anterior stomach in the males and females of the 5 mg/kg group, and cell infiltration in the lamina propria and submucosa and diffuse hyperplasia of squamous epithelium in the anterior stomach in the 50 mg/kg group. In addition, germinal center development in the hepatic lymph nodes in the males and females of the 50 mg/kg group and increased white blood cell count in the males of the 50 mg/kg group were noted as the secondary changes attributed to the inflammation of the stomach. In the kidneys, vacuolization of the renal tubular epithelium was observed in one female of the 50 mg/kg group. The relative weight of the kidneys increased in the males given 5 mg/kg and higher and females of the 50 mg/kg group and the absolute weight of the kidneys increased in the males and females of the 50 mg/kg group. In the surviving animals, soft feces, black soft feces and diarrhea were observed in the males and females of the 50 mg/kg group and pallor in the females of the 5 mg/kg group during the gestational period. One female in the 50 mg/kg group died on Day 23 of gestation and this animal also showed changes in the stomach and kidneys similar to the surviving animals. As the cause of death, bleeding from the stomach due to the administration of the test substance was considered.

In the recovery group, soft feces and black soft feces were observed until Day 1 of recovery but these resolved on the next day and thereafter. Diffuse hyperplasia of the squamous epithelium in the anterior stomach, squamous cell hyperplasia on the border and mucosal necrosis in the fundic gland area of the glandular stomach found in the stomach were alleviated compared to the findings at the end of the treatment period. No effect of the test substance was noted in the detailed observation, function test, body weight, food consumption, hematological examination or blood biochemical examination.

 

No effect of the test substance was noted in any of the examination items regarding repeoduction toxicity, including the sexual cycle, reproductive competence, fertility rate, delivering rate and nursing condition in parent animals and the birth rate, survival rate, sex ratio on Postnatal Day, sex ratio on 4 postnatal day, external appearance and body weight in offspring.

Based on the above, the no observed adverse effect level (NOAEL) for the repeated-dose toxicity of dichlone was estimated to be 0.5 mg/kg/day in both males and females because mucosal depression and ulcer in the anterior stomach were observed in the males and females given 5 mg/kg and higher. The NOAEL for the reproductive and developmental toxicity was judged to be 50 mg/kg/day, which was the highest dose level, as no abnormalities were noted in any of the examination items.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

0.5 mg/kg bw/day

Study duration:

subacute

Species:

rat

System:

gastrointestinal tract

Organ:

kidney

stomach

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

To assess the systemic toxicity profile of the test article a combined repeated-dose oral toxicity and reproductive and developmental toxicity study was conducted at 0, 0.5, 5 and 50 mg/kg/day using 12 male and 12 female Crl:CD(SD) rats per dose group in accordance with OECD TG422. The test substance was administered orally in males for 42 days from 2 weeks prior to mating and in females until Day 4 of lactation after parturition to examine repeated-dose toxicity and reproductive toxicity in parent animals and developmental toxicity in offspring. Autopsy was performed for 12 males and 12 females in the 0.5 and 5 mg/kg groups, and for 7 of 12 males and 7 of 12 females in the vehicle control group and the 50 mg/kg group at the end of the treatment period. Five remaining males and 5 females in the satellite group were examined for reversibility of the effects after 14-day withdrawal as the recovery group. The females in the recovery group were not mated in accordance with the test guideline.

Effects of the test substance were noted in the stomach and kidneys. In the stomach, the autopsy results revealed mucosal depression in the anterior stomach in the males and females of the 5 mg/kg group, and border elevation, mucosal roughening and wall thickening in the anterior stomach in the 50 mg/kg group. The histopathological examination showed ulcer in the anterior stomach in the males and females of the 5 mg/kg group, and cell infiltration in the lamina propria and submucosa and diffuse hyperplasia of squamous epithelium in the anterior stomach in the 50 mg/kg group. As the test substance has been reported to exhibit irritability in the rabbit skin (O’Neil, M.J., 2001), the changes in the stomach observed in this study were considered to be attributed to this irritability. Although ulcer was found in the anterior stomach of the 5 mg/kg group, the lesions observed in the 50 mg/kg group were cell infiltration in the lamina propria and submucosa of the anterior stomach, diffuse hyperplasia of the squamous epithelium, and squamous cell hyperplasia of the border alone but not ulcer. It was considered that, in the 50 mg/kg group, ulcers were observed in the early state of the treatment period leaving hyperplasia of the squamous epithelium as a repair picture at the end of the treatment period. In addition, germinal center development in the hepatic lymph nodes in the males and females of the 50 mg/kg group and increased white blood cell count in the males of the 50 mg/kg group were noted as secondary changes attributed to the inflammation of the stomach.

In the kidneys, vacuolization of the renal tubular epithelium was observed in one females of the 50 mg/kg group. This finding was judged as an effect of test substance administration by the authors of the report, however it was also seen in 1 female of the vehicle control group, therefore this finding might be not related to substance intake. Nevertheless, the kidney is a target organ, as shown by the relative weight increase of the kidneys in the males given 5 mg/kg and higher and females of the 50 mg/kg group. The absolute weight of the kidneys increased in the males and females of the 50 mg/kg group. The increase in the kidney weight of males also indicated the effect of the test substance administration but it was judged to be of poor toxicological significance because it was not associated with organic changes. Since the histopathological effects noted in females can also not clearly be correlated to the weight increase, the increase is considered as an adaptive effect. After recovery, the weight increase was no longer present.

In 1 female in the 50 mg/kg group that died on Day 23 of gestation, soft feces and black soft feces as well as mucosal depression in the anterior stomach, mucosal blackening in the glandular stomach, and discoloration of the kidneys were revealed at autopsy. The histopathological examination revealed diffuse hyperplasia of the squamous epithelium and ulcer in the anterior stomach, mucosal necrosis in the fundic gland area of the glandular stomach, vacuolization of the renal tubular epithelium, and atrophy of the spleen. Although occult blood in feces was not examined, bleeding from the stomach due to administration of the test substance was considered to be the cause of death because black feces, black contents considered to be coagulated blood in the intestines and increases in the percent reticulocyte count were observed in the 14-day dose-finding study conducted previously. In the surviving animals, soft feces, black soft feces and diarrhea were observed in the males and females of the 50 mg/kg group and pallor in the females of the 5 mg/kg group during the gestational period.

In addition, the food consumption increased in the females of the 50 mg/kg group before establishment of copulation, but it was a temporary change observed only on Day 14 of administration and, therefore, considered as an incidental change. The histopathological examination showed ultimobranchial rest in the thyroid gland in the males and females of the 50 mg/kg group, mineral deposition in the jejunal Peyer’s patches, localized myocarditis of the heart and round cell infiltration in the prostate in the males of the 50 mg/kg group, and mineral deposition in the cortico-medullary border of the kidneys and isolated cysts in the medulla in the females of the 50 mg/kg group. These changes were also found sporadically as spontaneous lesions in the vehicle control group and were judged to be incidental changes.

In the recovery group, soft feces and black soft feces were observed in the 50 mg/kg recovery group until Day 1 of recovery but these symptoms resolved on the next day and thereafter. Although diffuse hyperplasia of the squamous epithelium in the anterior stomach, squamous cell hyperplasia on the border and mucosal necrosis in the fundic gland area of the glandular stomach remained as changes in the stomach, the severities of these symptoms were alleviated compared to the findings at the end of the treatment period indicating that they were in the course of recovery.

Based on the above, the no observed adverse effect level (NOAEL) for the repeated-dose toxicity of 2,3-dichloro-1,4 -naphthoquinone was estimated to be 0.5 mg/kg/day in both males and females because mucosal depression and ulcer in the anterior stomach were observed in the males and females given 5 mg/kg and higher. Overall, the effects cause by test substance administration are mainly due to local irritation in the stomach. In addition, adaptive weight increases in the kidney are reported, however with no histological findings in males. In females there are histological findings in the kidney, but their correlation and toxicological relevance are questionable. Therefore, there is no conclusive systemic toxicity reported, and the substance is considered to be not classified for repeated dose toxicity. The irritation potential is addressed by classification with Skin irritation Cat 2 and Eye irritation Cat 2A.

Justification for classification or non-classification

Classification,Labelling, and Packaging Regulation (EC) No. 1272/2008

The available experimental test data are reliable and suitable for classification purposes under Regulation 1272/2008. As a result the substance is considered to be not classified for repeated dose toxicity under Regulation (EC) No. 1272/2008.