Teratogenic Effect of Excess Vitamin A on the limb development in mouse embryo

Background and Regarding to the developing organs in embryo and important role of vitamin (Vit)  on developing process in embryonic period, the present study was done in order to survey effects of excess Vit- administration on limb development and determine the optimum teratogenic dose of this substance and the critical time of its formation. This experimental study was done on 140 pregnant Swiss Webster strain mice. They were randomly divided into two control and experimental groups. The experimental group was subdivided into three groups as Â,B,Ç. Ône dose of 15000 ÏÜ/kg (at 8am), two doses of 10000 or 15000 ÏÜ/kg (at 8am & 18pm the same day) Vit  was injected interaperitoneally by insulin syringe on the day 9,10,11 or 12 days of gestation (vaginal plug = day 0 of gestation). The embryoes were removed on the 17th day. They were survied by Stereomicroscope and alcian blue- alizarin red S staining technique. Vit- gas produced major malformations in the forelimbs and hindlimbs of developing mouse embryos, such as short and unrotation limbs, short fingers, increasing interdigital cleft, also in ÇNS and Palate defects. Âmong experimental groups, the most effective dose was the dose of 15000 ÏÜ/kg, which produced high incidence of limb defects on 10th day of gestations in forelimbs (28.6%) and 11th hindlimbs (20.6%) compared to the control group (0%). Ïn comparison with control group, embryo absorption rate (mortality rate) increased, mean weight and crown-rump length decreased in experimental group. Which is significant according to MÂNÔV test (p< 0.001). Çonclusion: The results show that excess Vit_ is potent teratogen and produce limb malformations. The incidence and severity of these malforamations were correlated with the dosage and time of exposure. Ïf the embryo is exposed to excess Vit- during critical periods of developing limb, it may interfere with certain developmental Phenomena, resulting various limb defects among newborn infants.