Factors Affecting the Activity of Adenosine Triphosphatase and Other Phosphatases as Measured by Histochemical Techniques

Higher phosphatase activity toward ATP and other substrates occurred at alkaline pH in thin (5 µ), unfixed, frozen sections incubated in the medium described by Gomori ('41) than when treated with the medium employed by Maengwyn-Davies et al ('52). This difference in activities was caused principally by the salt content of the media. High sodium acetate concentration was strongly inhibitory to phosphatase activity toward adenosine triphosphate and α, β sodium glycerophosphate The pH optimum of phosphatase activity of frozen sections toward adenosine triphosphate varied with the composition of the incubating medium. The localization of phosphatase activity toward adenosine triphosphate in cardiac muscle varied with substrate concentration, with nuclear staining becoming more prominent with increased adenosine triphosphate concentrations. The localization of phosphatase activity was not affected by the concentrations of α,β sodium glycerophosphate and adenosine-5-phosphate used, but the most rapid staining occurred with the highest concentrations.