Ammonium 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoate

Toxicity to reproduction

Administrative data

Endpoint:

one-generation reproductive toxicity

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The mouse has a pharmacokinetically distinct profile as compared to the rat and monkey. Therefore, the mouse is not the appropriate or preferred test species for human risk assessment with this substance.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)

Deviations:

no

Remarks:

This study was conducted according to guidelines in effect at the time of study conduct. In addition, a toxicokinetic assessment of plasma levels of the test substance was performed in the F0 females on lactation day 21 and the F1 pups at culling (PND 4)

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: U.S. EPA OPPTS Guideline 870.3550

Deviations:

no

Remarks:

This study was conducted according to guidelines in effect at the time of study conduct. In addition, a toxicokinetic assessment of plasma levels of the test substance was performed in the F0 females on lactation day 21 and the F1 pups at culling (PND 4)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Reference substance 002

Cas Number:

62037-80-3

Details on test material:

- Purity: 84%

Test animals

Species:

mouse

Strain:

other: Crl:CD1(ICR)

Sex:

male/female

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: up to 14 days
- Proof of pregnancy: vaginal plug referred to as day gestation day 0 of pregnancy
- Further mating after one unsuccessful attempt: no
- After successful mating each pregnant female was caged (how): female was housed in an individual plastic cage with nesting material

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

The F0 males were dosed during study days 0 to 84 (70 days prior to pairing through 1 day prior to euthanasia), for a total of 84 to 85 doses. The females that delivered (with the exception of those females selected for toxicokinetic evaluation) were dosed from study day 56 through the day prior to euthanasia (14 days prior to pairing through lactation day 20) for a total of 53 to 64 doses. The females that were selected for toxicokinetic evaluation were dosed through the day of euthanasia (lactation day 21) for a total of 54 to 65 doses.

Frequency of treatment:

Daily

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 0.1, 0.5, 5 mg/kg/day
Basis:
nominal conc.

No. of animals per sex per dose:

Twenty five male and female rats from each dose group

Control animals:

yes, concurrent vehicle

Results and discussion

Results: P0 (first parental generation)

Effect levels (P0)

1

Dose descriptor:

NOAEL

Effect level:

5 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: The no-observed-adverse-effect level (NOAEL) for reproductive toxicity was 5 mg/kg/day, as no effects on reproduction were observed at any of the doses levels tested

2

Dose descriptor:

NOAEL

Effect level:

0.1 mg/kg bw/day

Based on:

test mat.

Sex:

male

Basis for effect level:

other: The NOAEL for systemic toxicity in F0 (P) male mice was 0.1 mg/kg/day based on the low incidences of single cell necrosis observed in the liver at 0.5 mg/kg/day.

3

Dose descriptor:

NOAEL

Effect level:

0.5 mg/kg bw/day

Based on:

test mat.

Sex:

female

Basis for effect level:

other: The NOAEL for systemic toxicity in maternal animals was 0.5 mg/kg/day. In maternal animals, this NOAEL was based on microscopic changes in the liver at 5 mg/kg/day.

Results: F1 generation

Effect levels (F1)

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

0.5 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: The NOAEL for systemic toxicity in offspring was 0.5 mg/kg/day. In the offspring, the NOAEL was based on body weight decrements in the F1 males and females in the 5 mg/kg/day group during the pre-weaning period.

Overall reproductive toxicity

Reproductive effects observed:

not specified

Any other information on results incl. tables

CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS)

- F0 survival was unaffected by test substance administration at all dosage levels. One F0 male each in the 0.1, 0.5, and 5 mg/kg/day groups was found dead or euthanized in extremis on study day 4, 55, or 56. One, 3, 1, and 1 F0 females in the control, 0.1, 0.5, and 5 mg/kg/day groups, respectively, were found dead or euthanized in extremis during lactation days 13-16. In the absence of a dose response and because mortality was also noted for 1 female in the control group, none of the moribundity or mortality noted in the test substance-treated F0 animals was attributed to test substance administration. Clinical findings noted included a body that was pale and cool to the touch, hypoactivity, labored respiration, and lacrimation at approximately 1-2 hours following dose administration on study days 2 and/or 3. Additional clinical signs consisted of hunched posture, decreased defecation, an immovable mass on the left lateral neck, red material around the eye, decreased respiration, and half-closed eyelids following dosing. In the absence of a dose response, none of the moribundity noted in the test substance-treated F0 animals was attributed to test substance administration. Other clinical findings noted in the surviving males and females in the test substance-treated groups, including hair loss and scabbing on various body surfaces, occurred infrequently, at a similar frequency in the control group, and/or in a manner that was not dose-related. A test substance-related increase in the incidence of unkempt appearance was observed in the majority of F0 females in the 5 mg/kg/day group at the detailed physical examinations and/or following dose administration during lactation days 4-10. This finding was only noted on 1-2 occasions per animal and therefore was not considered to be adverse.

BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)

- Test substance-related, higher mean F0 body weight gains were noted in the 5 mg/kg/day males for the first 7 weeks of dose administration. As a result, a higher mean body weight gain was noted in this group when the overall pre-mating (study days 0-69) and treatment (study days 0-84) periods were evaluated; the difference during the pre-mating period corresponded to increased mean food consumption during this same interval. Consequently, mean F0 body weights in the 5 mg/kg/day group males were 6.1% to 9.1% higher than the control group during study days 21-84. These test substance-related increases in body weight parameters for F0 males at 5 mg/kg/day were not considered adverse because they were of relatively minimal magnitude and were consistent with increases in food consumption and increased liver weights. In the 0.5 mg/kg/day group, a test substance-related higher mean body weight gain was observed during study days 0-7. However, mean body weight gains in this group were similar to the control group throughout the remainder of the treatment period and there were no corresponding effects on mean body weight or mean food consumption in this group; therefore this transient higher mean body weight gain was not considered to be adverse. Mean male F0 body weights, body weight gains, and food consumption in the 0.1 mg/kg/day group were unaffected by test substance administration. Test substance-related higher mean body weights (2% to 3% higher) and body weight gains were noted in the 0.5 and 5 mg/kg/day group F0 females during the pre-mating period. Mean F0 female body weights and body weight gains at 0.1 mg/kg/day and mean F0 female food consumption at 0.1, 0.5, and 5 mg/kg/day were unaffected by test substance administration during the pre-mating period. Test substance-related higher mean body weights and body weight gains with corresponding increased food consumption were noted in the 0.5 and 5 mg/kg/day groups compared to the control group during gestation. During lactation days 1-7, slightly lower mean body weight gains with corresponding reductions in mean food consumption were noted for the F0 females in the 5 mg/kg/day group. Mean body weights, body weight gains, and food consumption in this group were generally similar to the control group throughout the remainder of lactation. In the 0.5 mg/kg/day group, mean body weights, body weight changes, and food consumption were unaffected by test substance administration during lactation. Mean body weight in the 0.1 mg/kg/day group was slightly higher than the control group at the end of gestation on gestation day 18. This small increase was considered a possible consequence of the slightly larger litter sizes (mean of 12 pups per litter as compared to 11 pups per litter for the controls). The lack of any differences in body weight parameters immediately following delivery at the onset of lactation confirms the likelihood that the slight increase in body weight on gestation day 18 was related to litter size. Mean food consumption in the 0.1 mg/kg/day group was unaffected by test substance administration during gestation and lactation. Based on the magnitude of change and/or consistency with food consumption data, and/or increased liver weights and/or relationship to litter size, these test substance-related changes in body weight parameters noted in the F0 females were not considered adverse.

ORGAN WEIGHTS (PARENTAL ANIMALS)

Liver:

- In F0 males, mean absolute liver weights were increased 26% and 142% at 0.5 and 5 mg/kg/day, respectively, as compared to control values. Mean relative (% body weight) liver weights were increased 26% and 121%, respectively. An associated increase in mean final body weights in the high-dose males was entirely attributable to the marked increase in absolute liver weights. The increased liver weight parameters in the 0.5 and 5.0 mg/kg/day males was due to the microscopic finding of hepatocellular hypertrophy at these dose levels. The increases in both liver weights and final body weights were statistically significant (p<0.01)

- In F0 females, mean absolute liver weights were increased 26% and 101% at 0.5 and 5 mg/kg/day, respectively, as compared to control values. Mean relative (% body weight) liver weights were increased 18% and 81%, respectively. As in males, an associated increase in mean final body weights in the high-dose females was entirely attributable to the marked increase in absolute liver weights. Also as in males, the increased liver weight parameters in the 0.5 and 5.0 mg/kg/day females was due to the microscopic finding of hepatocellular hypertrophy at these dose levels. The increases in both liver weights and final body weights were statistically significant (p<0.01)

Kidney:

- In F0 males, mean absolute kidney weights were increased 8% in the 5 mg/kg/day dose group, as compared to the control value. The mean relative (% body weight) kidney weight was not increased. The slightly increased mean absolute kidney weight, which was not statistically significant, correlated with the microscopic finding of renal tubular cell hypertrophy.

- In F0 females, mean absolute kidney weights were increased 21% in the 5 mg/kg/day dose group, as compared to the control value. The mean relative (% body weight) kidney weight was increased 10%. Unlike males, there was no discernable microscopic tubular cell hypertrophy to account for the increased kidney weights. However, the increased mean absolute and relative (% body weight) kidney weights in the 5 mg/kg/day females were both statistically significant (p<0.01)

Other: - All other individual and mean absolute organ weight differences were considered to be spurious and unrelated to test substance administration. Statistically significant decreases in mean relative (% body weight) brain and epididymides weights were entirely due to the increased final body weights in the high-dose mice.

PATHOLOGY (PARENTAL ANIMALS) Test substance-related microscopic findings were observed in the liver of males and females (≥ 0.5 mg/kg/day) and kidneys of males (≥ 0.5 mg/kg/day).

- Liver: At necropsy, 3 of the surviving 5 mg/kg/day females had white areas on the livers that correlated with a slightly increased incidence of microscopic focal necrosis in this group. Therefore, it is likely that this gross finding was test substance-related. In the 5 mg/kg/day male and female dose groups, test substance-related hepatocellular hypertrophy was observed in all mice. The hypertrophy was graded mild (grade 2 of 4) to moderate (grade 3 of 4) in both males and females, although males were generally more affected. The hypertrophy was consistent with peroxisome proliferation and was characterized by increased hepatocellular size due an increase in cytoplasmic volume. The cytoplasm had fine eosinophilic stippling with H&E staining, giving it a granular appearance. All high dose males and most high dose females also had minimal to moderate single cell hepatocellular necrosis. A minimal (grade 1 of 4) to mild increase in hepatocyte mitotic figures was present in most males, while only 5/24 surviving females had increased mitoses, and these were graded as minimal. Similarly, increased pigment was observed in most males but only 5/24 females; all were graded as minimal. This pigment was within Kupffer cells and hepatocytes, and most likely represented lipofuscin. A slight increase in focal coagulative necrosis (all graded minimal) was observed in the high-dose females and was considered most likely test substance related. This finding correlated with the gross observation of increased white areas on the liver, although correlation of individual gross and microscopic lesions was not observed.

In the 0.5 mg/kg/day male and female dose groups, liver effects included only hepatocellular hypertrophy and single cell necrosis (males only). In males, hepatocellular hypertrophy was graded minimal to mild in the 12/24 affected mice. Five of these 12 mice also had minimal single cell necrosis. In females, the 14 affected mice with hepatocellular hypertrophy were all graded as minimal. Single cell necrosis in the 0.5 mg/kg/day was not increased over background incidence.

- Kidney: Test substance-related microscopic kidney effects were limited to an increase in the incidence of renal tubular cell hypertrophy in male mice given 0.5 and 5 mg/kg/day of the test substance. The incidence of this finding was dose-related but all lesions were graded as minimal. The hypertrophy was characterized by an increase in the size of renal tubular cells in the proximal tubular epithelium in the outer medulla beyond that seen in most control mice. The increased size of the tubular cells was due to increased finely granular eosinophilic cytoplasm. The hypertrophy, which was considered non-adverse, was not associated with any cellular degeneration and was consistent with the degree of hypertrophy seen occasionally in control male mice. The finding of one affected male mouse in the control and low-dose groups demonstrated the background incidence of this non-adverse finding.

The renal tubular hypertrophy in high-dose males correlated with the slightly (8%) increased mean absolute kidney weight in high-dose males. Although there was no microscopic hypertrophy observed in females, the increase in kidney weights was more pronounced in this sex.

- Reproductive: No test substance-related effects were observed on F0 reproductive performance (mating, fertility, or copulation indices, and mean days between pairing and coitus), mean gestation length, the process of parturition, mean numbers of implantation sites, or unaccounted-for sites. The failure of eleven F0 adult pairs to produce litters did not appear to be related to test substance administration. One low dose female had vaginal thickening suggestive of prolonged estrus which most likely was the cause of infertility. The cause of reproductive failure in the other 9 pairs was not determined.

OTHER FINDINGS (PARENTAL ANIMALS)

- Toxicokinetics: For both maternal animals and their offspring, male and female mice behaved in a kinetically similar manner, with an approximately linear relationship between dose and blood levels of the test substance. The mean maternal plasma concentration of the test substance measured 2 hours after dosing on day 21 of lactation were 903, 4966, and 36420 ng/mL in the 0.1, 0.5, and 5 mg/kg/day dose groups, respectively.

VIABILITY (OFFSPRING)

- Mean numbers of F1 pups born, live litter size, percentage of males at birth, postnatal survival, and the general physical condition of the F1 pups were unaffected by test substance administration at all dosage levels. F1 survival was unaffected by test substance administration at all dosage levels following weaning. One F1 male in the 5 mg/kg/day group and 1 female in the control group were euthanized in extremis on PND 22 and 24, respectively. Because the male pup in the 5 mg/kg/day group was extremely small in size, was the only surviving pup in that litter, and there was no other mortality noted in the F1 pups in this group; the moribundity in the 5 mg/kg/day group was not attributed to test substance administration.

CLINICAL SIGNS (OFFSPRING)

- A male in the 5 mg/kg/day group was euthanized in extremis on PND 22. On the day of euthanasia, body cool to the touch was noted for this male following dose administration. Additional clinical findings of a pale body and cyanosis were noted by the clinical veterinarian prior to euthanasia. This male was extremely small (6.5 g), was the only surviving pup in the litter, and in the absence of other mortality noted in the F1 pups in the 5 mg/kg/day group, this moribundity noted for male no. 5068-06 was not attributed to test substance administration. In the control group, female no. 4962-10 was euthanized in extremis on PND 24 due to an apparent mechanical injury. Gross findings noted for this female at necropsy included fractured nasal, frontal, and parietal bones, unilaterally. All other F1 animals in the control, 0.1, 0.5, and 5 mg/kg/day groups survived to the scheduled necropsy. No test substance-related clinical findings were noted at the weekly detailed physical examinations or approximately 1-2 hours following dose administration. Findings noted in the test substance-treated groups, including hair loss on the forelimbs, occurred infrequently, at similar frequencies in the control group, and/or in a manner that was not dose-related.

BODY WEIGHT (OFFSPRING) - A significantly (p<0.01) lower mean F1 male body weight gain was noted in the 5 mg/kg/day group compared to the control group during the first week of treatment (PND 21-28). Mean body weight gains in these animals were significantly (p<0.01) higher than the control group during PND 28-35 and similar to the control group during the remainder of the treatment period (PND 35-40). When the entire treatment period (PND 21-40) was evaluated, mean F1 male body weight gain in the 5 mg/kg/day group was similar to the control group. The reductions in mean body weight gain during PND 1-21 (pre-weaning) and PND 21-28 (treatment period) for the 5 mg/kg/day group males resulted in lower mean body weights for these animals throughout the treatment period (PND 21-40); the differences were significant (p<0.01) when compared to the control group. The greatest deficit was observed on PND 21 (23.0% lower) and by PND 40, mean body weights in the 5 mg/kg/day group were only 8.1 % lower than the control group.

A test substance-related significantly (p<0.01) higher mean F1 female body weight gain was noted in the 5 mg/kg/day group during PND 28-35. As a result, mean F1 body weight gain in the 5 mg/kg/day group females was significantly (p<0.01) higher than the control group when the entire treatment period was evaluated (PND 21-40). The higher mean body weight gains noted in the F1 females in the 5 mg/kg/day group were not considered to be adverse. Mean body weights in the F1 females in the 5 mg/kg/day group were 17.5 % and 9.3% lower than the control group on PND 21 and 28, respectively, because of the lower mean body weight gains in these animals during the pre-weaning period; the differences were significant (p<0.05 or p<0.01). However, by PND 35 and continuing throughout the remainder of the treatment period, mean body weights in the 5 mg/kg/day group females were similar to the control group.

Mean body weights and body weight gains in the F1 males and females in the 0.1 and 0.5 mg/kg/day groups were unaffected by test substance administration. Differences from the control group were slight and not statistically significant with the following exceptions. In the 0.1 mg/kg/day group females, a significantly (p<0.05) lower mean body weight gain was noted during PND 28-35 and a significantly (p<0.05) higher mean body weight was noted in this group on PND 28. These transient body weight effects were not attributed to test substance administration based on the absence of effects at 0.5 mg/kg/day.

SEXUAL MATURATION (OFFSPRING)

Male

- A significant (p<0.01) delay (2.6 days) in the age of attainment of balanopreputial separation was noted in the 5 mg/kg/day group compared to the concurrent control group. Mean ages of attainment were 27.6, 27.7, and 30.1 days in the 0.1, 0.5, and 5 mg/kg/day groups, respectively, compared to 27.5 days in the control group. The mean age of attainment in the 5 mg/kg/day group was within the historical control data range (29.1 to 33.8 days) and delays in the attainment of balanopreputial separation have been associated with decreases in mean body weights. Therefore, the delay in attainment of balanopreputial separation in the 5 mg/kg/day group was attributed to the test substance-related lower mean body weights (up to 23.0%) in this group prior to evaluation. Mean body weights at the age of attainment were 22.4 g, 22.6 g, and 20.9 g in the 0.1, 0.5, and 5 mg/kg/day groups, respectively, when compared to 22.0 g in the control group. No statistical differences were noted.

Female

- A significant (p<0.01) delay (3.4 days) in the mean age of attainment of vaginal patency was observed in the 5 mg/kg/day group compared to the concurrent control group. Mean ages of attainment were 27.6, 26.0, and 30.0 days in the 0.1, 0.5, and 5 mg/kg/day groups, respectively, compared to 26.6 days in the concurrent control group. The mean age of attainment in the 5 mg/kg/day group was within the historical control data range (25.9 to 32.1 days) and delays in the attainment of vaginal patency have been associated with decreases in mean body weights. Therefore, the delay in attainment of vaginal patency in the 5 mg/kg/day group was attributed to the test substance-related lower mean body weights in this group during the pre-weaning period and not a direct effect of test substance administration. Mean body weights at the age of attainment of vaginal patency were 18.9 g. 17.5g, and 17.9 g in the 0.1, 0.5, and 5 mg/kg/day groups, respectively, compared to 16.8 g in the concurrent control group; the differences were not statistically significant.

PATHOLOGY (OFFSPRING)

- At the scheduled F1 male and female necropsies, no test substance-related internal findings were observed at any dosage level. Macroscopic findings observed in the test substance-treated groups occurred infrequently, at similar frequencies in the control group, and/or in a manner that was not dose-related.

OTHER FINDINGS (OFFSPRING)

Toxicokinetics

- For both maternal animals and their offspring, male and female mice behaved in a kinetically similar manner, with an approximately linear relationship between dose and blood levels of the test substance. In PND 4 F1 pups, mean plasma levels were lower (approximately 2- to 4-fold) than the lactation day 21 maternal values. In PND 21 F1 pups, mean plasma levels of the test substance in all dose groups were markedly less (approximately 40-to 60-fold lower) than the respective lactation day 21 maternal values. In the F1 offspring samples on PND 40 that had been directly dosed since weaning on PND 21, mean plasma levels of the test substance in all dose groups were similar to those of the respective maternal dose groups sampled at PND 21. Evaluation of plasma levels of the test substance in dams and their offspring indicate that in mice, in utero exposure of fetuses to the test substance that are less than those of the orally dosed dam (PND 4 plasma levels) and that little or no exposure to nursing pups occurs during lactation (based on PND 21 plasma levels). In addition, plasma kinetics in juvenile mice directly dosed beginning at weaning appear to be equivalent to those of adult mice.

Applicant's summary and conclusion

Conclusions:

NOAEL Reproductive Toxicity F0 male/female = 5 mg/kg bw/day
NOAEL Systemic Toxicity F0 male = 0.1 mg/kg bw/day
NOAEL Systemic Toxicity F0 female = 0.5 mg/kg bw/day
NOAEL Systemic Toxicity F1 male/female = 0.5 mg/kg bw/day

Executive summary:

The test substance, in deionized water, was administered orally by gavage to 3 groups of Crl:CD1(ICR) mice, each group consisting of 25 males and 25 females. Dosage levels were 0.1, 0.5, and 5 mg/kg/day. F0males were approximately 6 weeks and F0 females were approximately 11 weeks of age at the beginning of test substance administration. The animals were paired for mating on a 1:1 basis within each treatment group after a minimum of 70 and 14 days of treatment for the males and females, respectively. In addition, a toxicokinetic assessment of plasma levels of the test substance was performed in the F0 females on lactation day 21 and the F1 pups at culling (PND 4), PND 21, and PND 40. 

 

All animals were observed twice daily for mortality and moribundity. Clinical observations, body weights, and food consumption were recorded at appropriate intervals. All F0 females were allowed to deliver and rear their pups until lactation day 21. Maternal blood samples were collected from 5 females/group at approximately 2 hours following dose administration on lactation day 21 for determination of test substance concentration in the plasma.

 

Clinical observations, body weights, and sexes were recorded for F1 pups at appropriate intervals. To reduced variability among the litters, 8 pups per litter, 4 per sex when possible, were randomly selected on PND 4 to continue on study and the remaining pups were culled. Blood samples (pooled by litter) were collected for toxicokinetic evaluation from the culled offspring of 10 litters/group. On PND 21, 1 male and 1 female pup per litter were selected for the F1. 

 

Complete necropsies were conducted on all F0 animals, and selected organs were weighed. Selected tissues of the reproductive system were examined microscopically from all F0 animals in the control and high-dose groups, all animals dying spontaneously or euthanized in extremis, and from any animals in the low- and mid-dose groups with impaired fertility (males that did not sire a litter or females that did not deliver a litter). In addition, the liver and kidneys from all F0 animals were examined microscopically. All F1 pups selected for study were observed twice daily for mortality and moribundity following weaning (PND 21) through study termination. F1males and females were dosed daily beginning on PND 21 through PND 40. Clinical observations, body weights, and food consumption were recorded at appropriate intervals. Indicators of sexual development (balanopreputial separation and vaginal patency) were evaluated for all surviving F1 animals. All surviving F1 animals were euthanized and necropsied on PND 40; blood samples for toxicokinetic evaluation were collected from 5 pups/sex/group at approximately 2 hours following dose administration.

 

There were no effects on reproduction (mating, fertility, or copulation indices, number of days between pairing and coitus, and gestation length). Test substance-related higher mean body weights, body weight gains, and food consumption were observed in the 5 mg/kg/day F0 males throughout the treatment period and 0.5 and 5 mg/kg/day group F0 females generally during gestation and lactation. These changes in body weight parameters in F0 males and females were not considered adverse. Increased liver weights and microscopic hepatocellular hypertrophy, consistent with peroxisome proliferation, were present in male and female F0 adults administered 0.5 or 5 mg/kg/day. Single cell necrosis of hepatocytes was also present in male mice in the 0.5 mg/kg/day dose group and in the males and females of the 5 mg/kg/day dose group. All other test substance-related microscopic changes in the livers of F0 male and female mice occurred at the 5 mg/kg/day dose level and included increased mitotic figures, lipofuscin pigment, and focal necrosis (females only). Microscopic renal tubular cell hypertrophy was present in F0 males given 0.5 and 5 mg/kg/day. An increase in mean absolute kidney weight was also present in body sexes given 5 mg/kg/day. No test substance-related effects were noted on postnatal survival. Lower mean offspring body weights and body weight gains were noted in the F1 males and females in the 5 mg/kg/day group during the pre-weaning period. 

Evaluation of the plasma levels of the test substance in dams and their offspring indicate that in mice, in uteroexposure of fetuses to the test substance results in plasma concentrations that are less than those of the orally dosed dam, and that little or no exposure to nursing pups occurs during lactation. Also, the plasma kinetics of the test substance in juvenile mice directly dosed beginning at weaning appeared to be equivalent to those of adult mice.

 

Based on these results, the no-observed-adverse-effect level (NOAEL) for reproductive toxicity was 5 mg/kg/day, as no effects on reproduction were observed at any of the doses levels tested. The NOAEL for systemic toxicity in F0 male mice was 0.1 mg/kg/day based on the low incidences of single cell necrosis observed in the liver at 0.5 mg/kg/day. The NOAEL for systemic toxicity in both maternal animals and their offspring was 0.5 mg/kg/day. In maternal animals, this NOAEL was based on microscopic changes in the liver at 5 mg/kg/day. In the offspring, the NOAEL was based on body weight decrements in the F1 males and females in the 5 mg/kg/day group during the pre-weaning period.