title: cAMP-associated inhibition of Na+-H+ exchanger in rabbit kidney brush-border membranes.
abstract: Adenosine 3',5'-cyclic monophosphate (cAMP) inhibits the rate of bicarbonate reabsorption and the rate of Na+-H+ exchange transport in the apical membrane of the proximal convoluted tubule. To study the relation between cAMP, cAMP-dependent protein kinase, and Na+-H+ exchange transport, brush-border membrane vesicles from the rabbit kidney were phosphorylated in vitro. The rate of proton gradient-stimulated amiloride-inhibitable 22Na+ uptake was measured as an index of Na+-H+ exchange transport activity. The inclusion of cAMP (10(-6) M) in a phosphorylating solution containing ATP decreased the 10-s uptake of amiloride-sensitive sodium from 2.25 +/- 0.21 nmol/mg protein in controls to 1.94 +/- 0.19 (P less than 0.001). Incubation of vesicles in the presence of purified catalytic subunit of cAMP-dependent protein kinase inhibited the amiloride-sensitive uptake of 22Na+ at 10 s from 2.35 +/- 0.49 nmol/mg protein to 2.05 +/- 0.44 (P less than 0.005). The inhibitory effect of both cAMP and catalytic subunit of cAMP-dependent protein kinase was blocked by the specific thermostable protein inhibitor of the kinase. These studies demonstrate that activation of endogenous membrane-bound cAMP-dependent protein kinase or exposure to exogenous catalytic subunit of cAMP-dependent protein kinase inhibits the rate of Na+-H+ exchange transport in the brush-border membrane of the rabbit kidney.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000037:antagonists & inhibitors*; D000242:Cyclic AMP / Q000494:pharmacology*; D005260:Female; D007672:Kidney Cortex / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D007700:Kinetics; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D017923:Sodium-Hydrogen Exchangers
chemical_list: D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011494:Protein Kinases