title: Prompt inhibition of arginine vasopressin-induced cellular adenosine 3',5'-monophosphate production by extracellular sodium depletion in rat renal inner medullary collecting duct cells in culture.
abstract: The present study was undertaken to determine whether the absence of extracellular Na+ affects cellular action of arginine vasopressin (AVP) in rat renal inner medullary collecting duct cells in culture. AVP increased cellular cAMP production in a dose-dependent manner. Na+ depletion promptly diminished the cellular cAMP response to AVP (1 nM AVP; 405.9 +/- 26.1 vs. 189.8 +/- 12.1 fmol/micrograms protein, P less than 0.01). The dose-response relation shifted to the right. The inhibition of the ability of AVP to produce cAMP was observed with an extracellular Na+ concentration less than 60 mM. Similar results were obtained with 2 x 10(-8) M forskolin, a diterpene activator of adenylate cyclase. Such inhibition was easily released, since only 10-min reexposure of the Na(+)-depleted cells to the control medium totally recovered the cAMP response to AVP. Extracellular Na+ depletion promptly decreased the cellular Na+ concentration from 15.8 +/- 1.0 to 5.4 +/- 0.6 mM (P less than 0.01), measured using the fluorescence dye sodium-binding benzofuran isophthalate. If the Na(+)-depleted cells were again incubated with the control medium, intracellular Na+ rapidly recovered to the precontrol level. Such a change was closely related to the change in cellular pH, which decreased from 7.19 +/- 0.02 to 6.97 +/- 0.02, measured using the fluorescence dye 2',7'-bis-(2-carboxymethyl)-5 (and -6)carboxyfluorescein,acetamethylester. However, Na+ depletion did not affect the cellular free calcium concentration or cellular protein and ATP contents. These results indicate that Na+ depletion promptly attenuated the ability of AVP to produce cAMP mediated through either the decrease in intracellular Na+ or cellular pH in renal inner medullary collecting duct cells.
authors.affiliation: Department of Medicine, Jichi Medical School, Tochigi, Japan.
authors.forename: S E
authors.initials: SE
authors.lastname: Ishikawa
authors.forename: K
authors.initials: K
authors.lastname: Okada
authors.forename: T
authors.initials: T
authors.lastname: Saito
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis*; 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; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D001127:Arginine Vasopressin; D012964:Sodium; D000242:Cyclic AMP; D002118:Calcium