Abstract: BACKGROUND ＆ AIM: To observe the toxic effects of Ethaselen on the maternal rat in late trimester of pregnancy, the growth and development, and the abilities of learning and reproduction of the offsprings. MATERIALS AND METHODS: SD pregnant rats were given Ethaselen orally from gestational day 15 to weaning day 28. The experimental groups received 250、500 and 1 000 mg/kg of Ethaselen. RESULTS： The body weight accretion of maternal rats (F0) in experimental groups was obviously lower than that in negative control group(P<0.05). The body_weight of the offsprings(F1) at birth and accretion during lactation were obviously decreased(P<0.05). The physiological indexes and neonatal reflexes were delayed significantly(P<0.05). But there were no toxic effects on the body weight gain, appetite, visceral measurements, mating ratio, pregnancy ratio and fetal development on stopping drug administration. CONCLUSION: Among the dose range used, Ethaselen caused obvious body weight accretion in F0 and F1, and developmental delay. But there were no the toxic effects on the visceral development, reproductive ability, body weight increase, and appetite on stopping the drug.

Key words: Ethaselen, rat, fetus, development, reproductive toxicity