Regulation of renal Na~+, K~+-ATPase and ouabain-sensitive H~+, K~+-ATPase by the cyclic AMP-protein kinase A signal transduction pathway

摘要

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 Wister 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~(-6) mol/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~(-6) 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 inhibitior of cytochrome P450-dependent arachiedonate 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.