Purification and characterization of specific endogenous ouabainlike substance from bovine adrenal

Endogenous inhibitors of Na, K-ATPase have been implicated in the pathogenesis of salt-induced hypertension. Despite an intensive search, the inhibitor(s) have long remained elusive. We have been able to purify such an inhibitor from methanol extracts of bovine adrenal glands by multiple steps of high-performance liquid chromatography (HPLC). This compound showed striking similarity to the cardiac glycoside ouabain in its dose dependency in the inhibition of Na, K-ATPase and Na-pump activity, competitive binding to the ouabain-binding site, and dependence of these effects on K+ concentration. These results indicate that vertebrate animals contain a regulator of Na, K-ATPase.