Assay of Sodium and Potassium Activated Adenosine Triphosphatase in Submicrogram Fragments of Renal Tubules

Abstract

An improved method for measuring Na, K-ATPase in submicrogram fragments of single renal tubules approximately one millimeter long is described. The activity is determined by coupling ATP hydrolysis stoichiometrically to pyruvate kinase and the oxidation of NADH by lactic dehydrogenase. NADH oxidation is followed fluorimetrically using an instrument specially modified for increased sensitivity and stability.