Microsomal ATPase of kidney papilla: sensitivity to diuretics and other inhibitors

Microsomal ATPase isolated from rat kidney papilla was compared to that from kidney medulla. Microsomal Na, K ATPase from papilla was more sensitive to inhibition by ouabain, Ca⁺⁺, N ethyl maleimide, Hg⁺⁺, thiomerin, ethacrynic acid and furosemide than the enzyme from the medulla. Mg ATPase of the papilla was less sensitive than the medullary enzyme to inhibition by Ca⁺⁺, Cd⁺⁺, N ethyl maleimide, Hg⁺⁺, ethacrynic acid and furosemide. Papillary Mg ATPase was less sensitive than papillary Na, K ATPase to all the inhibitors mentioned. Medullary Mg ATPase was more sensitive than medullary Na, K ATPase to inhibition by ethacrynic acid and furosemide but less sensitive than medullary Na, K ATPase to all the other inhibitors. Papillary Na, K ATPase is the most sensitive to inhibition and papillary possible significance of these characteristics is discussed.