Studies on the determination of Na-K-ATPase in red blood cell membranes.

The present paper is concerned with Na-K-ATPase. In the first part it deals with the effect of such factors as Na+, K+, Mg2+, ATP, pH on activity investigated using a soluble Na-K-ATPase from porcine cerebral cortex. In the second part a method for assaying red blood cell Na-K-ATPase is described. This method consists of specific steps for washing and preparation of red cell membranes, pretreatment of Na-K-ATPase with sodium dodecyl sulfate (SDS) and bovine serum albumin (BSA) and determination of enzymatic released inorganic phosphate. Na-K-ATPase prepared and treated in this way shows a higher activity than the conventionally prepared form of enzyme, as latent enzyme sites are exposed by the SDS treatment. The kinetic behaviour of Na-K-ATPase prepared and assayed by using this method is characterized and compared with that of soluble Na-K-ATPase.