Gadoliniumsulfite trihydrate

Endpoint summary

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:

1 April 2003 - 13 October 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

Environmental conditions:
Temperature and humidity were checked and recorded continuously. Room temperature: 20 - 22°C; Relative humidity: 39 – 55 %, The recordings were within the accepted range. Occasional transient fluctuations were not considered to affect the integrity of the study. Light-dark phases: 12 hours light, 12 hours dark, automatically controlled.

Housing and diet:
The rats were housed according to the German Animal Welfare Guidelines for housing of Laboratory Animals (Federal Ministry of Agriculture, Nutrition and Forests, October 13, 1977). They were kept individually under conventional conditions in Type III Makrolon® cages. Each cage was identified by a label indicating animal number and study number. Softwood granulate, analyzed periodically for contaminants, was used as the cage litter. The rats were fed pelletized Provimi Kliba standard diet No. 3433.0 and tap water ad libitum. Drinking water was available from Makrolon® drinking bottles freshly filled twice a week. The diet was checked periodically by an independent, approved laboratory, according to the regulations of the manufacturer. Analysis included both qualitative and quantitative evaluation for heavy metals, aflatoxins, pesticides, and antibiotics. Drinking water employed in this type of study is regularly analyzed microbiologically, physico-chemically, and chemically. The analytical results proved that the limits set by the German regulations for animal feed and human drinking water have been observed.

Route of administration:

oral: gavage

Details on route of administration:

Oral by gavage, once daily, 7 times a week. According to OECD guideline 407, the oral route was chosen. The volume of administration was 10 mL/kg body weight. The volume of administration per animal was calculated by means of the DATATOX F1 System.

Vehicle:

other: Aqueous 0.25% hydroxypropyl methylcellulose (Methocel® K4M Premium)

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

Preliminary analyses of Art. 170210 (gadolinium sulfite trihydrate) in aqueous 0.25% hydroxypropyl methylcellulose did not show consistent stability data due to problematic analytical methods. Therefore, as no method was available during the course of the study, the test material suspensions were prepared daily and an analysis was not performed.

Duration of treatment / exposure:

Oral by gavage, once daily, 7 times a week.

Frequency of treatment:

Oral by gavage, once daily, 7 times a week.

Dose / conc.:

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

Remarks:

Group 1; Control

Dose / conc.:

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

Remarks:

Group 2

Dose / conc.:

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

Remarks:

Group 3

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

Remarks:

Group 4

No. of animals per sex per dose:

Group 1 and 4: 10
Group 2 and 3: 5

Control animals:

yes

Observations and examinations performed and frequency:

Observations/Measurements Time schedule No. of rats/sex/group
Appearance and behavior daily 5 or 10
Mortality daily 5 or 10
Detailed clinical observations/ Predose, weeks 5/10
Functional observation battery 1, 2, and 3
Motor activity week 4 5
Functional observation battery week 4 5
Body weight once a week 5 or 10
Food consumption once a week 5 or 10
Water consumption twice a week 5 or 10
Hematology week 4 and 6 5
Clinical chemistry week 4 and 6 5
Urinalysis week 4 and 6 5

Sacrifice and pathology:

All rats surviving until the end of their scheduled treatment or recovery period were anesthetized by a carbon dioxide air mixture and exsanguinated by opening the abdominal vessels. They were subjected to a detailed necropsy and histopathological examination. The weights of 7 (females) or 9 organs (males) were recorded in all rats. The methods applied in pathology are described in the addendum Pathology.

Statistics:

All parameters were analyzed separately for each sex and time. To take the number of dose groups into account all the test procedures used maintain a multiple significance level of a= 0.05. Body weight, body weight gain, food and water consumption, and organ weights - relative and absolute - of the dose groups were compared with those of the control, using the multiple two-sided Dunnett-Test (1955, 1964). For the evaluation of the clinico-chemical parameters and the hematological parameters, the Wilcoxon rank sum test (Hollander and Wolfe, 1973) was used to make pairwise comparisons of the dose groups with the control group. The correction for multiple testing was done according to Bonferroni-Holm. Body weight, body weight gain, food and water consumption, organ weights, hematological and clinico-chemical parameters were evaluated within the DATATOX F1 system (data acquisition and laboratory management system, Instem LSS/Stone/UK). For the evaluation of the motor activity, mean values, standard deviation, and number of animals (N) were calculated. The individual values, mean values and standard deviations of the motor activity data are listed in tables. In addition, the cumulated data per animal are calculated for the following intervals (times listed as minutes after start of test): 0 - 20, 21 - 40, 41 - 60 and 0 - 60 (cumulated over the entire observation period). Mean values and standard deviations were calculated also for the cumulated data. For the cumulated data the control group was compared with the treated groups during 3 intervals (0-20, 21-40, 41-60), separately for males and females (2-sample Wilcoxon rank sum test, two-sided, exact). The results of this analysis have to be considered as explorative indicators rather than confirmatory evidence. Therefore, no correction for multiple testing was applied. In the tables, the test results were described by the symbols: - : p > 0.05; +: p ≤ 0.05 p describing the p value of the two-sided exact Wilcoxon test.

Clinical signs:

no effects observed

Description (incidence and severity):

Discharge from the nose was seen in one female rat of group 4 during days 19 to 29, and hair loss in one male rat of group 3 during the daily inspections.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

On day 25, male rat 1 of the control group scheduled for the main kill died during blood sampling.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Generally, the body weight and body weight gain were not impaired by the treatment with Gadoliniumsulfite trihydrate, although it seemed that there was a slight reduction in the body weight gain in group 3 (300 mg/kg) in males and females and in female group 4 (1000 mg/kg).

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

In the course of the study the rats treated with Art. 170210 showed some statistically significant deviations from the control. These deviations were of a mild degree and were all within the normal laboratory range.

Serum electrolytes: In study week 4, potassium was slightly increased in the females treated with 1000 mg/kg, chloride was slightly increased in the females treated with 100 mg/kg and inorganic phosphate was increased in the males at 1000 mg/kg. At the end of the recovery period, calcium was slightly decreased in the males at 1000 mg/kg and chloride in the females.

Serum enzymes: At the end of the treatment period, ALAT was slightly increased in the males at 100 and 300 mg/kg.

Urinalysis findings:

no effects observed

Description (incidence and severity):

The urine values of the male and female rats of groups 2 to 4 did not reveal any toxicologically relevant deviations. Urine volume and specific gravity were not altered by the treatment with Gadoliniumsulfite trihydrate.

Description (incidence and severity):

The motor activity was slightly increased in the males and decreased in the females during the recordings of 20 minutes intervals and in the total number of counts at 1000 mg/kg.

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

no effects observed

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Histopathological examinations revealed treatment-related changes in the stomach. They consisted of minimal to mild hyperplasia of mucous neck cells in the gastric fundus of 2 males and 1 female rat at 100 mg/kg. This finding was somewhat more pronounced in the 300 and 1000 mg/kg dose groups and almost all rats were affected. In addition, neutrophilic infiltrates in the submucosa, which were not observed at 100 mg/kg were noted at 300 and 1000 mg/kg. At the end of the 2 week recovery period 3 males and 4 females treated with 1000 mg/kg still showed a minimal to mild hyperplasia of mucous neck cells but without increased neutrophilic infiltrates in the submucosa. Therefore, the submucosal infiltration with granulocytes was completey reversible, whereas the hyperplasia of mucous neck cells was still present, but at a lower incidence and severity. Based on the findings observed at 1000 mg/kg at the end of the recovery, the findings observed in rats treated with 100 or even 300 mg/kg were considered to be completely reversible.

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Basis for effect level:

histopathology: non-neoplastic

Critical effects observed:

yes

Lowest effective dose / conc.:

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

System:

gastrointestinal tract

Organ:

stomach

Treatment related:

yes

Dose response relationship:

not specified

Relevant for humans:

not specified

Conclusions:

300 mg/kg were considered to be the NOAEL (no observed adverse effect level) because the changes seen were considered to be reversible based on the histopathological results seen at 1000 mg/kg at the end of the recovery period. 1000 mg/kg were considered not to be tolerated by the rats due to slight deviations in the FOB and motor activity and histopathological findings which were not fully reversible at the end of the recovery period.

Executive summary:

Gadoliniumsulfite trihydrate was administered orally by gavage, once daily, 7 times a week for 4 weeks to 3 groups of male and female HsdCpb:WU Wistar rats. A similarly constituted control group received the vehicle, aqueous 0.25% hydroxypropyl methylcellulose, and served to generate contemporary control data. The control and high dose groups consisted of 10 male and 10 female rats each. The low and mid dose groups consisted of 5 male and 5 female rats each. At the end of the treatment period 10 (5 males and 5 females) rats were scheduled for necropsy. The remaining rats of groups 1 and 4 were scheduled for a 2 week recovery period. The rats were kept under conventional conditions. All rats were subjected to macroscopic and histopathological examinations. Seven (females) or 9 organs (males) were weighed from each surviving rat at the end of the treatment or recovery periods. On day 25, male rat 1 of the control group scheduled for the main kill died during blood sampling. There were no clinical symptoms during the daily observations which could be related to the treatment with Art. 170210. The functional observation battery (FOB) revealed significantly decreased arousal on days 10, 18, and 22 in male rats at 1000 mg/kg. All other changes were not considered to be treatment related. The motor activity was slightly increased in the males and decreased in the females during the recordings of 20 minutes intervals and in the total number of counts at 1000 mg/kg. Body weight, body weight gain, food, and water consumption were not impaired by the treatment with Gadoliniumsulfite trihydrate at doses of up to 1000 mg/kg. Hematology did not reveal any treatment-related effects. Clinical chemistry did not reveal any toxicological deviations. Urine weight, specific urinary gravity, and urinalysis did not reveal any toxicologically relevant changes. At necropsy only spontaneous alterations were observed. There were no treatment related organ weight changes in comparison to the control group. Histopathological examinations revealed treatment-related changes in the stomach. They consisted of minimal to mild hyperplasia of mucous neck cells in the gastric fundus of 2 males and 1 female rat at 100 mg/kg. This finding was somewhat more pronounced in the 300 and 1000 mg/kg dose groups and almost all rats were affected. In addition, neutrophilic infiltrates in the submucosa, which were not observed at 100 mg/kg were noted at 300 and 1000 mg/kg. At the end of the 2 week recovery period 3 males and 4 females treated with 1000 mg/kg still showed a minimal to mild hyperplasia of mucous neck cells but without increased neutrophilic infiltrates in the submucosa. Therefore, the submucosal infiltration with granulocytes was completey reversible, whereas the hyperplasia of mucous neck cells was still present, but at a lower incidence and severity. Based on the findings observed at 1000 mg/kg at the end of the recovery, the findings observed in rats treated with 100 or even 300 mg/kg were considered to be completely reversible. 300 mg/kg were considered to be the NOAEL (no observed adverse effect level) because the changes seen were considered to be reversible based on the histopathological results seen at 1000 mg/kg at the end of the recovery period. 1000 mg/kg were considered not to be tolerated by the rats due to slight deviations in the FOB and motor activity and histopathological findings which were not fully reversible at the end of the recovery period.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

300 mg/kg bw/day

Study duration:

subacute

Species:

rat