Background: Consuming high doses of vitamin A during pregnancy may lead to malformations in the offspring. Some reports state that low doses that do not cause macroscopic abnormalities may result in mental and behavioral disorders. However, there are few studies on the microscopic effects of these doses on the organism. Objective: The aim was to investigate the effects of early prenatal exposure to different doses of oral vitamin A on the fetal liver. Materials and methods: Twenty-five pregnant rats, divided into five groups, received oral vitamin A at doses of 10,000, 50,000, 100,000, and 200,000 IU/kg between days 10 and 12 of gestation. The fetuses were collected on day 19 of gestation, their livers were dissected, and histology, apoptosis, and proliferation were examined by hematoxylin-eosin, TUNEL assay, and Ki67 immunolabeling using stereological methods. Results: Vitamin A decreased fetal liver volume, the number of Ki67-positive cells per unit volume, and the total number of hepatocytes at all doses except 10,000 IU/kg (p<0.001). Consequently, apoptosis was significantly higher in the groups receiving 100,000 and 200,000 IU/kg vitamin A (p<0.001). Conclusion: Our study shows that vitamin A administered during gestation days 10-12 has a suppressive effect on the developing rat liver when the dose exceeds 10,000 IU/kg, probably due to increased apoptosis and suppressed cell division.
Keywords: Vitamin A; cell count; fetus; hepatocytes; liver; teratology.