1 alpha, 25-Dihydroxy-vitamin D-3 regulates ATP-dependent calcium transport in basolateral plasma membranes of rat enterocytes.

Basolateral plasma membrane vesicles of rat small intestinal epithelium accumulate calcium through an ATP-dependent pumping system. The activity of this system is highest in duodenum and decreases towards the ileum. This distribution along the intestinal tract is similar as the active calcium absorption capacity of intact intestinal epithelial segments. ATP-dependent calcium uptake in basolateral membrane vesicles from duodenum and ileum increased significantly after repletion of young vitamin D-3-deficient rats with 1 alpha,25-dihydroxy-vitamin D-3. Ca2+ -ATPase activity in duodenal basolateral membranes increased to the same extend as ATP-dependent calcium transport, but (Na+ + K+)-ATPase activity remained unaltered.