Effects of HCl on Alkaline Phosphatase in Kidney and Intestine: Histochemical and Quantitative Study.

Abstract

Sections of acetone-fixed kidney and intestine from mouse, guinea pig and dog were placed for 30 min. at 37[degree]C in solns. of HCl ranging from pH 5.0-1.8; then rinsed in distilled water and studied for alkaline phosphatase by the Gomori technic. Exposure to HCl at pH 2.6 or lower completely inactivated renal alkaline phosphatase in all 3 species. Intestinal phosphatase was more resistant, being inactivated at pH 1.9, 2.0, and 2.2 in the 3 species respectively. Comparable results were obtained in quantitative studies of fresh tissue homogenates, employing the phenolphthal-ein phosphate substrate of Huggins and Talalay for phosphatase detns. In a mixed homogenate containing equivalent amts. of renal and intestinal alkaline phosphatase, the enzymes from kidney and intestine appeared to retain their individuality with respect to inactivation by HCl. It had previously been shown that in the mouse, intestinal alkaline phosphatase was more sensitive than renal phosphatase to inhibition by cyanide[long dash]just the reverse of their relative sensitivity to inactivation by HCl. These findings supported the view that renal and intestinal alkaline phosphatases are not identical.