Regulation of renal NAplus, Kplus-ATPase and ouabain-sensitive Hplus, Kplus-ATPase by the cyclic AMP-protein kinase A signal transduction pathway

We investigated the effect of the cyclic AMP-protein kinase A (PKA) signalling path­way on renal Na+ ,K+ -ATPase and ouabain-sensitive H+ ,K+ -ATPase. Male Wistar rats were anaesthetized and catheter was inserted through the femoral artery into the ab­dominal aorta proximally to the renal arteries for infusion of the investigated sub­stances. Na+ ,K+ -ATPase activity was measured in the presence of Sch 28080 to block ouabain-sensitive H+ ,K+ -ATPase and improve specificity of the assay. Dibutyryl-cyclic AMP (db-cAMP) administered at a dose of 10-7 mol/kg per min and 10 -6mol/kg per min increased Na+ ,K+ -ATPase activity in the renal cortex by 34% and 42%, respec­tively, and decreased it in the renal medulla by 30% and 44%, respectively. db-cAMP infused at 10- mol/kg per min increased the activity of cortical ouabain-sensitive H+,K+ -ATPase by 33%, and medullary ouabain-sensitive H+,K+ -ATPase by 30%. All the effects of db-cAMP were abolished by a specific inhibitor of protein kinase A, KT 5720. The stimulatory effect on ouabain-sensitive H+ ,K+ -ATPase and on cortical Na+ ,K+ -ATPase was also abolished by brefeldin A which inhibits the insertion of pro­teins into the plasma membranes, whereas the inhibitory effect on medullary Na+ ,K+ -ATPase was partially attenuated by 17-octadecynoic acid, an inhibitor of cytochrome P450-dependent arachidonate metabolism. We conclude that the cAMP-PKA pathway stimulates Na+ ,K+ -ATPase in the renal cortex as well as ouabain-sensitive H+ ,K+ -ATPase in the cortex and medulla by a mechanism requiring insertion of proteins into the plasma membrane. In contrast, medullary Na+ ,K+ -ATPase is inhibited by cAMP through a mechanism involving cytochrome P450-dependent arachidonate metabolites.