Intrauterine hypervitaminosis A and lung maturation in newborn rats

Abstract

Time mated adult rats were administered 100,000 IU of vitamin A daily for a period of 5 days in the 1st  and 3rd trimester of the pregnancy (Days 2-6, and Days 16-20 in Group A and B respectively). The pregnant rats were allowed to litter after 21 days, and the newborn pups were collected and the lungs harvested and processed. A significantly reduced mean weight of the pup from groups A and B was observed compared to
Group C which was not administered Vitamin A during pregnancy. The reduction was however more striking in the group A pups compared to the group B pups, though the weight of group B pups were significantly lower
than that of the control group. In addition to the significant weight reduction, the groups A and B pups had extensive desquamation of the respiratory epithelium in the bronchiole, bronchi and alveoli. There was also associated poor delineation of the alveoli in the experimental groups. However, the cilia of the desquamated epithelium remain intact. The anomalies were worse in the group A pups than in the group B pups. The
respiratory epithelial defect associated with hypervitaminosis A might explain the degree of still birth particularly in the Group A pups. The features of the anomaly are closely related to respiratory distress syndrome which is known to occur in state of low vitamin A during development. This shows that hypo and hypervitaminosis during respiratory development results in features that are similar, the only exception being the state of epithelial ciliation.

Keywords: Alveolus, bronchiole, respiratory epithelium, vitamin A, atelectasis.