Abstract

The effects of vitamin D-deficiency and repletion on the distribution and activities of Ca2+-ATPase, phytase, and alkaline phosphatase in intact epithelial cells isolated from different regions of the villi and the crypts of the rat jejunum were studied. Similar distribution patterns of activities were found for the three enzymes. In all cases, the enzyme levels were the highest at the villus tip and gradually declined to low activities in the crypt. The Kms were very different between cells in the crypt base and those at the villus tip, the highest Kms being found in the crypt. The activities of these enzymes were reduced in the entire length of the villus in vitamin D-deficient rats. Recovery of the enzymatic levels was observed on vitamin D repletion, but at different rates. Total recovery of activity of Ca2+-ATPase, phytase, and alkaline phosphatase was observed after 18, 24, and 36 hours, respectively, after a single dose of 6.5 nmol (2.5 micrograms) vitamin D3. Enzymatic activities in the crypt cells were not affected by vitamin D3 treatment. These data suggest that Ca2+-ATPase, phytase, and alkaline phosphatase may be distinct entities, and that their activities in the crypt cells may not be vitamin D-dependent.