Short-term regulation of the proximal tubule Na+,K+-ATPase: Increased/decreased Na+,K+-ATPase activity mediated by protein kinase C isoforms

In different species and tissues, a great variety of hormones modulate Na+, K+ -ATPase activity in a short-term fashion. Such regulation involves the a ctivation of distinct intracellular signaling networks that are often hormo ne- and tissue-specific, This minireview focuses on our own experimental ob servations obtained by studying the regulation of the rodent proximal tubul e Na+,K+ -ATPase. We discuss evidence that hormones responsible for regulat ing kidney proximal tubule sodium reabsorption may not affect the intrinsic catalytic activity of the Na+,K+ -ATPase, but rather the number of active units within the plasma membrane due to shuttling Na+,K+ -ATPase molecules between intracellular compartments and the plasma membrane. These processes are mediated by different isoforms of protein kinase C and depend largely on variations in intracellular sodium concentrations.