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Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route
Dose descriptor:
NOAEL
1 000 mg/kg bw/day
Additional information

The objective of this study was to evaluate the effects of the analogue substance 2 (refer to IUCLID chapter 13), on the integrity and performance of male and female reproductive systems, including gonadal function, estrous cycle, mating behavior, conception, gestation, parturition, lactation, weaning, and growth and development of the offspring.

This study consisted of 3 treatment groups and 1 vehicle (0.5% aqueous carboxymethylcellulose) control group (26 rats per sex per group). The animals were exposed to the test article daily via oral gavage throughout 2 consecutive generations. The test article was administered at dose levels of 0, 100, 300, and 1000 mg/kg/day at a constant volume of l0 mL/kg. The duration of the entire study was approximately 9 months. Adult rats were paired after a growth (premating) period of at least 10 weeks for P and F1 parental rats.

Observations for clinical signs and measurement of body weights and food consumption were performed pretest (P generation only) and during the premating, gestation, and lactation periods in adult animals from both generations. Estrous cyclicity in P and F, females was evaluated beginning 3 weeks before and continuing throughout mating. Fertility of adults was evaluated. Sperm count, motility, and morphology were determined for all adult males. Selected organs from adult animals were collected, weighed, preserved, and microscopically examined. Gross lesions from selected control and 1000 mg/kg/day P and F, parental animals were microscopically examined.

Parameters recorded for offspring included survival at birth and during lactation, litter size, individual pup weights and sex at birth and during lactation, gross abnormalities, and clinical observations. Sexual maturation (vaginal opening and preputial separation) was measured in F1 pups selected as parents for the second generation. Selected F1 and F2 weanlings were subjected to a necropsy, and specified organs were weighed and preserved.

A total of 3 animals from the P generation and 8 animals from the F1 generation died or were euthanized in extremis during the study. None of these deaths, however, were considered to be test article related. No effects on parental body weight, food consumption, or macroscopic and microscopic observations were noted during the premating, gestation, or lactation periods in either parental generation. A test article-related increase in kidney weight (absolute and relative) was evident in P females and F1 males and females at 1000 mg/kg/day. No test article-related effects on reproductive performance were noted for either parental generation.

Mating, fertility, and fecundity indices, copulatory interval, gestation length, sperm analysis and primordial follicle count (in F1 animals only) parameters were considered to be comparable between concurrent control and treatment groups or within historical control

range for this laboratory.

No adverse, test article-related changes in growth or development of offspring were noted in either the F1 or F2 generations. Body weight was higher in F1 pups from all treatment groups when compared with controls, but although this was considered to be test article-related, the effect was not considered to be adverse or biologically significant. Other measured parameters that included litter size at birth (total, live and stillborn), survival during lactation, sexual maturation in the F1 animals, clinical observations, and macroscopic and microscopic observations and organ weights were considered to be comparable between control and treatment groups.

Based on the results of this study, the No Observed Adverse Effect Level (NOAEL) for parental toxicity was 300 mg/kg/day and for parental reproductive performance, the NOAEL was 1000 mg/kg/day. For offspring growth and development, the NOAEL was also

l000 mg/kg/day.


Short description of key information:
Two-generation study according to EPA OPPTS 870.3800 (Reproduction and Fertility Effects) in male & female rats (Sprague-Dawley) via oral: gavage. F0 Parents were treated from 70 days before mating until euthanasia at doses of 100, 300 and 1000 mg/kg bw/day (actual ingested)
F1 pubs were exposed indirectly in utero and during lactation. F1 parents were exposed directly (via gavage) starting when the youngest selected animal had reached an age of 28 days until euthanasia. The dosing regime was 7 days/week for all animals. F2 pubs were treated in uteroa and via lactation.

Effects on developmental toxicity

Description of key information
Two studies were performed using an analogue substance 2 (refer to IUCLID chapter 13):
1) A prenatal developmental toxicity study according to EPA OPPTS 870.3700 in rats (Sprague-Dawley) treated via oral gavage. The dose range was 100, 400, and 1000 mg/kg bw (actual ingested) applied on 7 days/week. Animals were exposed from day 6 through day 19 of gestation.
3) A prenatal developmental toxicity study according to EPA OPPTS 870.3700 in rabbits (New Zealand White) treated via oral gavage. The dose range was 100, 400, and 800 mg/kg bw (actual ingested) applied on 7 days/week. Animals were exposed from day 7 through day 28 of gestation
Effect on developmental toxicity: via oral route
Dose descriptor:
NOAEL
400 mg/kg bw/day
Additional information

Rat Developmental Toxicity Study using the analogue substance

2 (refer to IUCLID chapter 13)

This study consisted of 3 treatment groups and 1 vehicle control group (30 time-mated females/group). Dose levels of 0, 100, 400 and 1000 mg/kg/day were administered via oral gavage daily on days 6 through 19 of gestation at a volume of 10 mL/kg. The females were time mated upon delivery. The day on which evidence of copulation was observed was considered to be day 0 of gestation. Observations of dams included clinical signs, gestational body weights and food consumption. Litters were delivered by cesarean section on day 20 of gestation. Gravid uterine weights were recorded. Total number of implantations, early and late resorptions, live and dead fetuses, and sex and individual body weights of fetuses were recorded. External abnormalities of fetuses were recorded. Approximately one-half of the fetuses were examined for visceral abnormalities, and the remaining fetuses were examined for skeletal abnormalities (bone and cartilage).

No mortalities were observed during the study, and the only test article-related clinical observation noted was discoloured faeces. No changes in maternal body weight, body weight gain, or food consumption were noted in the treatment groups when compared with the vehicle control group. No test article-related necropsy findings were seen in uterine parameters, including numbers of corpora lutea, implantations, live fetuses, and resorptions, gravid uterine weight, and adjusted body weight and body weight gain were comparable between vehicle controls and treatment groups. Pre- and post-implantation losses were similar among all groups, and no test article effects were noted. Fetal external, visceral, and skeletal evaluations did not reveal any test article-related effects. All findings were either comparable with the concurrent vehicle control and/or historical control incidences.

Based on the results of this study, the No Observed Effect Level (NOEL)for both maternal and developmental toxicity in rats was 1000 mg/kg/day, the highest dose tested. The analogue substance 2 (refer to IUCLID chapter 13)

, was not teratogenic in rats following oral administration of doses up to and including 1000 mg/kg/day.

Rabbit Developmental Toxicity Study using the analogue substance

2 (refer to IUCLID chapter 13)

 

This study consisted of 3 treatment groups and 1 vehicle control group (25 females/group). The female rabbits were time mated at receipt. The rabbits received the test article once daily via oral gavage at dose levels of 100, 400, and 800 mg/kg/day. The dose volume was 10 ml/kg. Exposure initiated on day 7 of gestation and continued to and included day 28 of gestation. Observations of does included clinical signs, gestational body weights and food consumption. Litters were delivered by cesarean section on day 29 of gestation. Gravid uterine weights were recorded. Total number of corpora lutea, implantations, early and late resorptions, live and dead fetuses, and individual sex and body weights of fetuses were recorded. All fetuses were examined for external, visceral, and skeletal abnormalities (bone and cartilage).

Excessive maternal toxicity, as evidenced by mortality, statistically significant decreases in body weight gain and food consumption as well as an increase in abortions, was observed at 800 mg/kg/day. As a result, this group was terminated prior to completion of the study. Less severe maternal toxicity was observed at 400 mg/kg/day.

Two does died in the control group, but these deaths were a result of technical gavage error or mechanical injury. A total of 8 does from the 800-mg/kg/day group died during gestation and another high-dose doe was euthanized in extremis. An additional 7 does from the high dose group aborted during the study.

No treatment-related mortality was noted at 100 or 400 mg/kg/day. A doe in the 400 mg/kg/day group was considered to be moribund, but died prior to being euthanized. Necropsy findings suggested that this animal died due to gavage-related injury. Treatment-related clinical observations at 400 mg/kg/day included soft faeces and discoloured stool. No changes in body weight, body weight gain or food consumption were noted at 100 or 400 mg/kg/day. Necropsy findings in does from the 800 mg/kg/day group included discoloration of the liver, oedematous and/or discoloured stomach, red discoloured and/or oedematous intestines bloody an/or mucoid contents in the intestines. The rabbit in the 400 mg/kg/day group that aborted had an oedematous stomach and liquid, bloody contents in the intestines at necropsy which were also considered to be treatment related.

No effects on uterine parameters were noted at 100 or 400 mg/kg/day. Numbers of corpora lutea., implantations, live and dead fetuses and resorptions were comparable between the vehicle control and the 100 and 400 mg/kg/day groups. Fetal body weights were statistically lower at 400 mg/kg/day when compared with the vehicle control group.

Based on treatment-related clinical observations and necropsy findings seen in does at 400 mg/kg/day, the No Observed Effect Level (NOEL) for maternal effects in this study was 100 mg/kg/day, the lowest dose tested. There were statistically significant decreases in fetal body weight at 400 mg/kg/day. These changes may have been secondary to the maternal toxicity observed in this study and were not considered to be an indication of developmental toxicity. There was no indication that the analogue substance

2 (refer to IUCLID chapter 13)

, caused increases in malformations and, consequently, was not considered to be teratogenic in rabbits.

Justification for classification or non-classification