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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Remarks:
combined repeated dose and reproduction / developmental screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
December 2002 - February 2003
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Conducted to GLP and OECD Guidelines.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2006
Report Date:
2006

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
Date received: 14 August 2006
Description: off-white powder
Storage conditions: ambient temperature and humidity in the dark

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
A sufficient number of male and female Sprague-Dawley Crl:CD (SD) IGS BR strain rats were obtained from Charles River UK. On receipt the animals were examined for signs of ill health or injury. The animals were acclimatised for 16 days during which time their health status was assessed. A total of eighty animals (forty males and forty females) were accepted into the study. At the start of the treatment the males weighed 298 to 375g and the females weighed 200 to 248g.
Upon arrival, the animals were housed in groups of four in polypropylene cages with stainless steel grid floors and tops, suspended over paper-lined polypropylene trays. During the mating period animals were transferred to a similar type cage on a one male to one female per cage basis.
Following evidence of successful mating, the males were returned to their original cages and transferred to a separate animal room of comparable conditions. The females were housed, individually, in polypropylene cages with solid floors and stainless steel tops. Mated females were given softwood chips, as bedding, throughout gestation and lactation.
The animals were allowed free access to food and water. A ground diet PMI 5002 was offered ad libitum. Main water was supplied from polycarbonate bottles attached to the cage. The diet and drinking water were considered not to contain any contaminant at a level that might have affected the purpose or integrity of the study.
The animals were housed in air conditioned rooms. The rate of air exchange was at least fifteen air changes per hour and the low intensity fluorescent lighting was controlled to give twelve hours continuous light and twelve hours darkness. Environmental conditions were continuously monitored by a computerised system. Both animal rooms used for this study were maintained to operate within a target temperature range of 21 +/-2 degC and a relative humidity range of 55 +/- 15%. On isolated occasions the room temperature and/or humidity fell outside the protocol limites but this was not considered to have affected the purpose or integrity of the study.
The animals were allocated to dose groups using a randomisation procedure based on stratified bodyweights and the group mean bodyweights were then determined to ensure similarity between the dose groups.
The animals were uniquely identified within the study, by an ear punching system routinely used at the laboratory. Colour coded cage labels were used to assist recognition of dose groups.

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
Experimental Preparation:
The test material was prepared as a direct dietary admixture. For which dose level, an appropriate aliquot of test material was weighed and then added to approximately one third of the required amount of untreated diet in a mixing bowl. For week 1 test diet preparation the test material and diet were mixed for 20 minutes, for each dose level using a Hobart QE 200 mixer. For subsequent test diet preparations an initial mix of the test material and diet was performed using a Hobart QE 200 mixer for ten minutes. Further untreated diet was then added to the initial mix to give the required concentration and the entire amount was then mixed for ten minutes using the Hobart QE 200 mixer.
Prior to the start of the study, samples of test diet preparation were analysed for achieved concentration, homogenicity and stability of test material in diet. The results of analysis of the original preparations showed the test material to be stable for at least 14 days. Subsequent preparations of the dietary admixtures were performed weekly. Samples of these preparations were taken on three occasions during the study to determine the achieved concentration of test material in the dietary admixture.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The concentration of test substance in the dietary formulations was determined by high performance liquid chromatography (HPLC) using an external standard technique. Prior to the start of the study, samples of the dietary formulations were analysed for homogeneity, stability, and validation of the dietary dose group concentrations. The results of analysis of the original preparations showed the test material to be stable for at least 14 days. Subsequent preparations of the dietary admixtures were performed weekly. Samples of these preparations were taken on three occasions during the study to determine the achieved concentration of test material in the dietary admixture.
Duration of treatment / exposure:
47 days
Frequency of treatment:
Daily
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
Initial: 1000ppm; Adjusted: 900ppm after 29 days
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
Initial: 2750ppm; Adjusted: 2500ppm after 29 days
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
Initial: 7500ppm; Adjusted: 6750ppm after 29 days; Adjusted: 5500ppm after 33 days
Basis:
nominal in diet
No. of animals per sex per dose:
Control: 10 male, 10 female
1000ppm: 10 male, 10 female
2750ppm: 10 male, 10 female
7500ppm: 10 male, 10 female
Control animals:
yes, plain diet
Details on study design:
-Groups of ten male and ten female rats were dosed according to dose groups for fourteen days prior to pairing.
-All animals were given a detailed clinical examination once every week for four weeks to observe functional/behavioral changes in an open arena.
- One day prior to pairing (Day 13) five males and five females, randomly selected, were sampled for clinical chemistry and haematology.
- On Day 14 all animals were paired on a one male: one female basis within each dose group for a maximum of fourteen days.
- At the observation of mating or at the end of the fourteen day mating period males were returned to their original cages and females were transferred to individual cages.
- At the end of the mating phase five males per dose group were evaluated for functional/sensory responses to various stimuli. The males used were thosed selected for haematology/clinical chemistry.
- Pregnant females were allowed to give birth and maintain their offspring until Day 4 postpartum. Evaluation of each litter size and weight were performed during this period.
- At Day 4 postpartum, five females per dose group were evaluated for functional/sensory responses to various stimuli. The females used were those selected for haematology/clinical chemistry.
- At Day 5 postpartum following completion of functional assessments all females and offspring were killed and examined macroscopically.
- Following completion of the female gestation and lactation phases, the males were killed and examined macroscopically.

Examinations

Observations and examinations performed and frequency:
Morbidity/Mortality:
All animals were checked twice daily during the normal working week and once daily at weekends.

Clinical Observations:
All animals were observed daily, immediately before and one hour after dosing, for clinical signs of toxicity.

Functional Observations:
On the day of initiation of treatment and on Days 8, 15 and 22, all animals were observed for signs of functional/behavioural toxicity. Functional performance tests were also performed on five selected females per group on Day 22 for males and Day 4 of lactation for females, together with an assessment of sensory reactivity to difference stimuli.

Behavioural Assessments:
Detailed individual clinical observations were performed for each animal using a purpose built arena. The following parameters were observed:
Gait
Tremors
Twitches
Convulsions
Bizarre/Abonormal/Steriotypic behaviour
Salivation
Pilo-erection
Exophthalmia
Lachrymation
Hyper Hypothermia
Skin colour
Respiration
Palpebral closure
Urination
Defecation
Transfer arousal
Tail elecation

Functional Performance Tests:
- Motor Activity
Twenty purposes built 44 infra-red beam automated activity monitors were used to assess motor activity. Animals of one sex were tested at each occasion and were randomly allocated to the activity monitors. The tests were performed at approximately the same time each day, under similar laboratory conditions. The evaluation period was five hours for each animal. The percentage of time each animal was active and mobile was recorded for the overall five hour period and also during the final 20% of the period (considered to be the asymptotic period). The motor activity for females at 2750 ppm was not recorded as females were killed in extremis prior to evaluation.
- Forelimb/Hindlimb Grips Strength
An automated grip strength meter was used. Each animal was allowed to grip the proximal metal bar of the meter with its forepaws. The animal was drawn along the trough of the meter by the tail until its grip was broken. The animal was drawn along the trough of the meter by the tail until its hind paws gripped the distal metal bar. The animal was pulled by the base of the tail until its grip was broken. A record of the force required to break the grip for each animal was made. Three consecutive trials were performed for each animal. Fore and hinf limb grip strength was not recorded for females at 2750 ppm as females were killed in extremes prior to evaluation.
-
Sensory Reactivity:
Each animal was individually assessed for sensory reactivity to auditory, visual and proprioceptive stimuli. The following parameters were observed:
Grasp response
Vocalisation
Toe pinch
Tail pinch
Finger approach
Touch escape
Pupil reflex
Startle reflex
Blink reflex
The sensory reactivity for intermediate level females was not recorded as the females were killed in extremis prior to evaluation.

Bodyweight:
During the maturation and mating period the parental generation animals were weighed weekly. Following mating the parental males were weighed weekly until termination. Parental generation females showing evidence of mating were weighed on Days 0, 7, 14 and 20 post coitum. Parental generation females with a live litter were weighted on Days 1 and 4 post partum.

Food Consumption:
During the maturation period, food consumption was recorded for each cage of adults weekly. For females showing evidence of mating, food consumption was recorded for the periods covering Days 1 to 7, 7 to 14 and 14 to 21 post coitum. For females with live litters, fod consumption was recorded for the period covering Days 1 to 4 post partum.

Food conversion efficiency was determined as:
Food conversion ratio = group mean body weight gain (g bw/day) during week / group mean food consumption (g food/rat/day) ”

Laboratory Investigations:
Haematological and blood chemical investigations were performed on five males and five females selected from each test and control group on Study Day 13. Blood samples were obtained from the lateral tail vein. Animals were not fasted prior to sampling.

Haematology:
The following parameters were measured on blood collected into tubes containing potassium EDTA anti-coagulant:
Haemoglobin (Hb)
Erythrocryte count (RBC)
Haematocrit (Hct)
Erythrocyte indices - mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV), mean corpuscular haemoglobin concentration (MCHC)
Total leucocyte count (WBC)
Differential leucocyte count - neutrophils (Neut), lymphocytes (Lymph), monocytes (Mono), eosinophils (Eos), basophils (Bas)
Platelet count (PLT)
Prothrombin time (CT) was assessed by 'Hepato Quick' and Activated partial thromboplastin time (APTT) was assess by 'Preci Clot' using samples collected into sodium citrate solution (0.11 mol/L).

Blood Chemistry:
The following parameters were measured on plasma from blood collected into tubes containing lithium heparin anti-coagulant:
Urea
Glucose
Total protein (Tot. Prot)
Albumin
Albumin/Globulin (A/G) ratio (by calculation)
Sodium (Na+)
Potassium (K+)
Chloride (Cl-)
Calcium (CA++)
Inorganic phosphorus (P)
Aspartate aminotransfease (ASAT)
Alanine aminotransfease (ALAT)
Alkaline phosphatase (AP)
Creatinine (Creat)
Total cholestrol (Chol)
Total bilirubin (Bili)(



Sacrifice and pathology:
At Day 5 of lactation all the surviving adults, including non-fertile animals, were killed by carbon dioxide asphyxiation; followed by exsanguination by cardiac puncture for selected animals and cervical dislocation for unselected animals. All animals were examined macroscopically for both internal and external abnormalities. Selected organs and tissues were retained in fixative.
The following list of organs was weighed for all animals at necropsy where applicable:
Adrenals
Brain
Epididymides
Heart
Kidneys
Liver
Ovaries
Spleen
Testes
Thymus
Paired organs were weighed together.

Tissue preservation:
Samples of the following tissues were preserved from all animals in buffered 10% formalin except where stated:
Adrenals
Aorta (thoracic)
Bone & bone marrow (femur including stifle joint)
Bone & bone marrow (sternum)
Brain (including cerebrum, cerebellum and pons)
Caecum
Colon
Duodenum
Epididymides (preserved in bounds fluid)
Eyes
Gross lesions
Heart
Ileum
Jejunum
Kidneys
Liver
Lungs (with bronchi) (inflated to normal inspiratory volume with buffered 10% formalin before immersion in fixture)
Lymph nodes (cervical and mesenteric)
Mammary gland
Muscle (skeletal )
Oesophagus
Ovaries
Pancreas
Pituitary
Prostate
Salivary glands (submaxillary)
Sciatic nerve
Seminal vesicles
Thyroid/parathyroid
Trachea
Urinary bladder
Uterus + Cervix
Vagina
Coagulating gland
Skin (hind limb)
Spinal cord (cerviacl)
Spleen
Stomach
Testes (preservedf in bouins fluid)
Thymus
Urinary bladder
Uterus

Histopathology:
The tissues listed above were examined from five males and five females selected from the control and high dose groups. Histopathology was extended to include examination of the liver, spleen, pituitary, salivary glands and sternum for five males and five females selected from both the low and intermediate dose groups.
The following list of tissues were examined from the remaining unselected males and females from the control and high dose groups:
Epididymides
Ovaries
Pituitary
Prostate
Seminal vescles with coagulating gland
Uterus and cervix
Vagina

Statistics:
- Endpoint group 1: Adult male and female bodyweight during the maturation, gestation and lactation periods, adult male food consumption, female food consumption during maturation, gestation and lactation, litter size, litter weight, individual offspring bodyweight offspring landmarks of physical development, haematology, blood chemistry and organ weights: Values were analysed to establish homogeneity of group variances using Levene's test followed by one-way analysis of variance. If the variances were unequal subsequent comparisons between control and treated groups were performed using a pairwise 'T' test Comparison Method. If variances were equal, subsequent comparisons between control and treated groups were performed using Dunnett's Multiple Comparison Method. For haematology and blood chemistry values, an additional regression analysis of all values was also performed.
- Endpoint group 2: Adult pre-coital intervals, female gestation lengths, offspring reflexological responses and litter sex ratios, relative organ weights: Individual values were compared using the Kruskal-Wallis non-parametric rank sum test. Where significant differences were seen, pairwise comparison of control values against treated group values was performed using Mann-Whitney "U" test.
- Histopathology: For those tissues from selected animals only. Chi-squared analysis for differences in the incidence of lesions occurring with an overall frequency of 1 or greater. For the comparison of severity grades for the more frequently observed conditions, Kruskal-Wallis one-way non-parametric analysis of variance.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Food efficiency:
effects observed, treatment-related
Description (incidence and severity):
food conversion
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
not examined
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
no effects observed
Details on results:
Mortality:
One high dose female (number 71) was killed in extremis during the late gestation phase of the study due to possible dystocia. At the intermediate dose level a total of eight females were killed in extremis during the gestation phase of the study. Six of the eight female mortalities were found to have offspring in utero at post mortem examination indicating possible impairment of parturition.
There were no mortalities at the low dose level or the control level.

Clinical Observations:
The treatment related clinical signs at the high dose were associated with the majority of females and one male. The most prevalent of findings were hunched posture and pilo-erection. Clinical signs of toxicity were seen early in the treatment period with hunched posture observed from week 2 and pilo erection from week 5 along with sporadic instants of tip-toe gait. These findings did not persist throughout the course of the study as the remaining nine high dose female animals showed no clinical signs of toxicity at the end of the treatment. One male also showed clinical signs of hunched posture during the treatment period.
Two intermediate dose level females showed hunched posture and three showed pilo erection, but the onset of these findings was later than those seen in high dose females.
No clinical effects were observed for males at this dose level.
At the low dose level there were no clinical signs of reaction to treatment.

Behavioural Evaluations:
The behavioural evaluation showed no evidence to suggest any significant treatment related observations associated with behavioural change. There was no indication of a treatment related effect on sensory reactivity to various stimuli or an effect on motor activity.

Bodyweight (maturation/pre-mating and males post-mating; see Section 7.8.1 for female bodyweight findings during gestation and lactation):
At the high dose level there was a reduction in group mean bodyweight for males during the first week of treatment which resulted in a statistically significant difference (p<0.001) compared to control values at Week 2 and 3 of the study. Subsequent bodyweight gain for males and females prior to mating was lower than control value and the difference in group mean bodyweight remained statistically significant (p<0.001). Post mating bodyweight gain was inconsistent and differences in group mean values remained statistically significant (p<0.001) compared to control values.
At the intermediate dose level there was a reduction in male bodyweight gain, which resulted in lower group mean bodyweight compared to control values. The difference was statistically significant (p<0.001) from Week 4 of the study until termination. There was no significant effect on female bodyweight gain prior to mating.
At the low dose level there was a reduction in male bodyweight gain which resulted in lower group mean bodyweight compared to control values. The difference was statistically significant (p<0.o5) from Week 4 until termination. There were no significant effects upon female bodyweight gain prior to mating.

Food Consumption :(maturation/pre-mating and males post-mating; see Section 7.8.1 for female food consumption findings during gestation and lactation):
At the high dose level there was a marked reduction in group mean food consumption for males and females prior to mating. This reduction in food consumption was also evident for males during the post mating phase of the study.
At the intermediate dose level there was a reduction in group mean food consumption for males and females prior to mating. The reduction in food consumption was also evident for males during the post mating phase of the study.
At the low dose level there was a reduction in make and female food consumption prior to mating. Post mating male food consumption was reduced compared to control values.

Food conversion:
Due to the low number of females with live litters, food conversion ratio evaluation is restricted to pre-mating only. At the high dose level the food conversion ratio for females was notably lower than control values during the first week of treatment whereas the male value was higher than control. The post mating food conversion ratios for males were inconsistent compared with control values.
At the intermediate dose level both male and, more obviously, female values were lower than controls prior to mating. Post mating male values were more comparable with controls.
At the low dose level male or female food conversion ratios prior to mating or for males post mating were comparable with control values.

- Chemical intake
As the high and intermediate dose level, there was an increase in test material intake for males and females in the second week of treatment prior to mating which reflects the increased food consumption seen. This was also seen for females at the low dose level, Post mating male test material intake was lower during the sixth week of the study which reflects the reduction in dose levels for all the treated groups.

Hematology:
At the high dose level there was a slight decrease in platelet count for males compared to control values. The differences was statistically significant (p<0.01). There was a slight increase in clotting time for females compared to ctrol values. The difference was statistically signicant (p<0.05). There was a reduction in mean cell volume and an increase in activated partial thromboplastin time for males only, which was statistically significant (p<0.01) compared to control values.
At the intermediate dose level there was a slight reduction in mean cell volume for males only. The difference was statistically significant (p<0.05) compared to control values.
At the low dose level there were no significant treatment related effects seen in the haematological parameters examined.

Clinical Chemistry:
At the high dose level notable statistically differences, compared to control values were associated with decreased plasma phosphorus values for both sexes (p<0.01), decreased plasma chloride for males and females (p<0.01 and p<0.001 respectively), increased plasma cholesterol for both sexes (p<0.001) and an increased plasma creatinine (p<0.001) for males only. The statistically significant difference for plasma bilirubin for females (p<0.05) was considered to be incidental.

At the intermediate dose level notable statistically significant differences compared to control values were associated with a decreased plasma phosphorus for males and females (p<0.01 and p<0.001 respectively), an increased plasma cholesterol for males and females (p<0.001 and p<0.05 respectively) a decreased plasma chloride for females only (p<0.01) and an increased plasma creatinine for males only (p<0.05). A reduction in plasma aspartate aminotransferase for females (p<0.01) was also observed which is considered to be incidental.

At the low dose level statistically significant differences when compared to control values were associated with a decreased plasma phosphorus for both sexes (p<0.05) and an increased plasma cholesterol for both sexes (p<0.01) and an increased plasma creatinine for males only (p<0.05).


Organ Weights:
At the high dose group the low number of pregnant females resulted in too few animals of the same physiological status as the control group females to allow direct comparison of organ weights. Statistically significant reductions in male absolute organ weight values compared to control values were observed for kidneys, epididymides, heart, thymus, spleen (p<0.001) and adrenals (p<0.01). Only the spleen and thymus weight relative to bodyweight was significantly lower than controls (p<0.01). The weight of testis and brain relative to bodyweight were significantly higher (p<0.001) than controls but this is likely to be fortuitous and a result of reduced bodyweight among males. The increase in liver weight, relative to bodyweight (p<0.001), may well represent a true effect of treatment.
At the intermediate dose group the low number of females at termination resulted in too few animals to allow for a meaningful evaluation. Statistically significant reductions in male absolute organ weight values were observed for kidneys, epididymides, spleen and thymus (p<0.01) plus adrenals and heart (p<0.01). Only the difference for the thymus weight, relative to bodyweight, remained statistically significant (p<0.001). Liver weight, relative to bodyweight was significantly higher (p<0.05) than controls. An increased brain and testis weight, relative to bodyweight, was considered to be fortuitous and directly related to lower bodyweights among males.
At the low dose group statistically significant reductions in organ weights were observed for thymus and spleen (p<0.001) kidneys (p<0.01) and heart (p<0.05) for males and adrenals (p<0.001) and heart (p<0.05) for females. Concomitant statistically significant reductions in organ weight, relative to bodyweight, were seen for spleen (p<0.01) and thymus (p<0.001) in males and females (p<0.01).

Histopathology:
LIVER:
Centrilobular hepatocyte enlargement was observed in relation to treatment for rats of with sex of all treatment levels. Hepatocyte enlargement is commonly observed in the rodent liver following the administration of xenobiotics and, in the absence of associated inflammatory or degenerative changes, is generally considered to be adaptive in nature.

SPLEEN:
Generally lower grades of severity of extramedullary haemopoiesis and higher grades of severity of pigment accumulation were observed in relation to treatment in high dose females. An effect at the intermediate dose level was difficult to determine but at the low dose level the effect on haemopoiesis was in the opposite direction with generally higher grades of severity of the condition prevailing compared with the control group. The toxicological significance, if any, of this finding is uncertain. There was probably no effect on pigment deposition at the intermediate dose level and no effect at the low dose level. Male rats were not similarly affected.

PITUITARY:
Higher grades of severity of cellular vacuolation in the pars anterior were seen for rats of either sec treated with the high and intermediate dose levels and for male rats only of the low dose group.

THYROIDS:
Generally higher grades of severity of follicular cell hypertrophy were seen in relation to treatment for rats of either sex of all treatment groups.

SALIVARY GLANDS:
Lower severity grades of serous secretion in the submandibular glands were more prevalent among rats of either sex of all treatment groups compared with the controls.

BONE MARROW:
Higher grades of severity of adipose infiltration, representing myeloid hypoplasia, were seen in relation to treatment for rats of either sex treated at the high and intermediate dose levels, and for male rats only of the low dose level.

HEART:
Focal myocarditis was observed in several controls and treated rats and is a common background entity in laboratory maintained rats. The severity of the condition was never greater than minimal, or one or two foci, and should not be interpreted as being indicative of any ongoing myocardial disease.

LIVER:
Scattered mononuclear cell foci were observed in the majority of animals examined in the study. Such are commonly observed in the rodent liver and are not indicative of any adverse condition at the severities encounted.

KIDNEYS:
Isolated groups of basophilic tubules are frequently encountered in the renal cortex of laboratory maintained rats and have no pathological significance at the severities or frequencies reported in this study. Similarly focal mineralisation is a commonly observed background condition amongst female rats.

LUNGS:
A minimal severity of bronchus associated lymphoid tissue was reported for most animals examined in the study and is not indicative of respiratory disease. Minor severities and low incidences of focal pneumonitis and accumulations of alveolar macrophages are commonly observed pulmonary changes in laboratory maintained rats of this age and are not suggestive of significant respiratory disease.

MAMMARY GLAND:
Glandular hyperplasia was observed in the mammary tissue of all female control rats examined and in two female high dose rats. The appearance of the mammary tissue is consistent with pregnancy and lactation and the group distribution of the condition in this study is not a primary effect of treatment but related to the incidence of pregnancy.

All remaining morphological changes were those commonly observed in laboratory maintained rats of the age and strain employed and, since there were no differences in incidence or severity between control and treatment groups, all were considered to be without toxicological significance.


Effect levels

Dose descriptor:
LOAEL
Effect level:
60 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: LOAEL, 900/1000 ppm diet (60 mg/kg bw/day) based on test material, m/f, multiple systemic effects.

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
The administration of ZMB2 to male and female Sprague-Dawley rats at dose levels up to 7500 ppm diet (adjusted to 6750 ppm and then to 5500 ppm), for a period of up to 47 days, resulted in various treatment-related systemic effects. At the lowest dose (60 mg/kg bw/day), these effects included decreased male body weight gain, reduced food consumption, changes in clinical chemistry, decreased relative organ weights for spleen, thymus, and female adrenals, and positive histopathology for male spleen, male pituitary, thyroid, salivary gland, and male bone marrow. Inclusive of higher dose effects, the primary systemic effect was described as altered metabolic state. The No Observed Adverse Effect Level (NOAEL) for repeated dose toxicity was not established.