NaK-ATPase in rat pancreatic islets

Abstract

Summary Shifts in the distribution of the monovalent cations Na⁺ and K⁺ between the extra-and intracellular space seem to be important for the secretory response of the β-cell. An attempt was therefore made to study the enzyme responsible for monovalent cation transport, the (NaK)-activated ATPase. In the presence of NaN₃ as inhibitor of the mitochondrial Mg-ATPase, a NaK-ATPase with a specific activity of 72 mU×mg protein⁻¹ could be demonstrated in crude membrane preparations of rat pancreatic islets. The enzyme, which was inactive in the absence of Mg⁺⁺, needed both Na⁺ and K⁺ for activation and was inhibited by ouabain and PCMB. The main part of the NaK-ATPase was localized in the microsomal fraction. Glucose, sulphonylureas, somatostatin and diazoxide were with-out effect on NaK-ATPase.