The effect of vitamin D on enzyme activities in the mucosal cells of the chick small intestine.

A search was made for enzyme activities that are increased after vitamin D treatment of rachitic chicks. Three enzyme activities located in the brush borders of the mucosal cells of the intestine - ATPase, p-nitrophenyl phosphatase, and pyrophosphatase - were found to approximately double in activity 48 hr after vitamin D was given. The ATPase and the p-nitrophenyl phosphatase required Mg(++) for activity but could be further stimulated by addition of Ca(++). The three activities are probably caused by the same enzyme since 20 mM phenylalanine inhibited all three activities. It is unlikely that the Ca(++)-stimulated ATPase is concerned with Ca(++) translocation since phenylalanine, which inhibits this enzyme, had no effect on(45)Ca transport from mucosal to serosal fluids of everted sacs of intestine.