Augmentation of forskolin-induced cAMP production by ouabain in rat renal papillary collecting tubule cells in culture.
The effect of extracellular calcium (Ca2+) on the cellular action of forskolin was studied using a Na+, K(+)-ATPase inhibitor ouabain in rat renal papillary collecting tubule cells in culture. Forskolin-induced cAMP production was enhanced by the pretreatment of cells with ouabain, providing that a dose-dependent curve with forskolin shifted to the left. The enhancement by ouabain of cellular cAMP production in response to forskolin was totally blunted by cotreatment with cobalt, verapamil, or Ca2(+)-free medium containing 1 mM EGTA. In addition, two dissimilar antagonists of calmodulin, namely trifluoperazine and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W - 7), attenuated the ouabain's effect on cAMP production in response to forskolin. These results therefore indicate that ouabain enhances the activation of adenylate cyclase by forskolin, mediated through cellular free Ca2+, in renal papillary collecting tubule cells, and that extracellular Ca2+ is an important source for cellular Ca2+ mobilization by ouabain.
Ishikawa
S
S
Department of Medicine, Jichi Medical School, Tochigi, Japan.
Saito
T
T
D000818:Animals; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D005576:Colforsin; D010042:Ouabain; D000242:Cyclic AMP