The developmental toxicity potential of ametryn was assessed, involving teratogenic and reproductive studies on 180 and 170 presumed pregnant albino mice respectively, given doses of 0, 292, 438, 584 and 779 mg kg~1 day~1, orally on days 6È15 of presumed gestation. During the gestation period, body weight, food consumption, water intake, mortality and general behavioural changes were recorded. On day 18, mice for teratogenic studies were killed and some parameters assessed. There were more deaths for the 584 mg kg~1 day~1 (31%) and 779 mg kg~1 day~1 (49%) groups than for the 438 mg kg~1 day~1 (10%) and 292 mg kg~1 day~1 (0%) groups. Reductions in mean body weight gain during exposure and post-exposure periods were recorded for the two highest dose levels ; however, the corrected maternal weight (minus the uterus) remained unchanged for all the groups. Di †erences in food consumption and water intake were insigniÐcant at all dose levels. Teratogenic parameters such as litter size decreased at the two highest doses as a result of signiÐcant resorptions and abortions. Other parameters such as termed fetuses per litter, fetal body weight, placental weight, crownÈrump length and tail length, were reduced sig-niÐcantly. No external, visceral or skeletal changes were observed except delayed ossiÐcation. These results show that ametryn is embryotoxic to mice at 584 mg kg~1 and above. The 170 presumed pregnant mice allowed to (F 0 ) deliver pups did so after 20(^2) days and pups obtained from matured F 1 F 2 F 1 (not given any ametryn) were also delivered after 20(^1) days.
There was pup weight reduction for the two highest doses whereas pups F 1 F 2 showed a non-signiÐcant reduction only for 779 mg kg~1 day~1 group. fetal F 1 viability was 50È75% before day 4 and 75È99% after day 4 for the two highest doses compared to 100% survival for other dosage groups. No deaths were recorded for generation pups. Food and water intakes, crownÈrump length F 2 and tail length increments were insigniÐcant for both generations. The appearance of developmental milestones like pinna attachment, hair growth, vaginal opening and testes descension remained una †ected for all the doses, but times of incisor eruptions, eye and ear opening were slightly lengthened for generation F 1 at 779 mg kg~1. This observation was not noted in generation pups. A F 2 battery of behavioural tests conducted for and pups did not reveal changes F 1 F 2 in movements such as pivoting, negative geotaxis reÑex nor in post-weaning test such as consummatory activity and activity wheel. The growth of the skeletal system was una †ected by ametryn after day 10 post-delivery generation) and (F 1 day 0 generation. Ametryn has little or no e †ect on reproductive and/or (F 2 ) developmental characteristics of mice at doses below maternal toxicity. 1998