Comparative studies of acid and alkaline phosphatase activities in nonvascular smooth muscle membranes

Acid and alkaline phosphosphatase activities of subcellular fractions isolated from rat gastric muscle and vas deferens by differential centrifugation, sucrose density gradient and cation-induced aggregation methods were studied using p-nitrophenyl phosphate as the substrate. Alkaline phosphatase and a large portion of acid phosphatase activities were found to be of plasmalemmal origin. Acid and alkaline phosphatase activities were different in the effect of Mg2+, fluoride, vanadate, EDTA and resistance to heat inactivation suggesting that these two phosphatase activities were not expressed by the same enzyme.