Assay of Na-K-ATPase in cultured nephron epithelia.

Microenzymatic methods have been utilized in the past to quantify the activity of Na-K-ATPase in tubular segments of the mammalian nephron. The assay reported here measures the precipitated inorganic phosphate liberated by the hydrolysis of gamma-32P-ATP. Activity data in single nephron segments of the cortical collecting tubule (CCT) confirm previous work; specifically, first data on enzyme activity in small cultured cell populations derived from CCT demonstrate that the Na-carrier enzyme can be quantified in nephron cell cultures.