Effect of vitamin A on small intestinal brush border enzymes in a rat

Weanling male rats fed a vitamin A deficient (VAD) diet were compared with rats fed the same diet supplemented with vitamin A. Half of the VAD group was repleted with vitamin A at the age of 70 days. There was a decline in weight in the VAD group after 45 days. Serum and liver retinol concentrations were negligible in the VAD groups at 70 days of age. These levels returned to normal in the repleted group within 20 days of supplementation. Histological observations in the intestinal tissues of the experimental animals exhibited reduced villus height (p < 0.05) compared with the vitamin A supplemented group (VAS), reduced number of mucous secreting goblet cells and total enterocytes. In addition, a significantly higher number of proliferating cells was found along the crypt. Disaccharidases (sucrase and maltase), peptidases (gamma GT) and alkaline phosphatase activities were markedly lower along the brush border (p < 0.05) in the VAD group compared to the VAS group. We also determined the total DNA, RNA and protein in the jejunal tissues per 0.1 mg/tissue in both groups. The RNA production per cell in the VAD groups was notably lower than that of the controls (p < 0.05). Our observation indicates that brush border enzyme levels are altered in animals with vitamin A deficiency, and that phenomenon is augmented when calculated per single cell. This change may be attributed to direct effects of vitamin A on the rate of proliferation and differentiation of the epithelial tissue along the jejunum rather than to gross structural changes along the small intestine.