title: pH dependence of inhibition of arginine vasopressin-induced adenosine 3',5'-monophosphate production by cellular sodium depletion in rat renal inner medullary collecting duct cells in culture.
abstract: The present study was undertaken to determine whether the change in cellular Na+ concentration ( [Na+]i) or cellular pH (pHi) is essential for the modulation by Na+/H+ antiporter of the cellular action of arginine vasopressin (AVP) in renal inner medullary collecting duct cells in culture. Extracellular Na+ depletion promptly decreased [Na+]i from 15.8 to 5.4 mM (P less than 0.01), which was closely related to the decrease in pHi (7.19 to 6.97; P less than 0.01). In the presence of 0.5 mM 3-isobutyl-1-methylxanthine, AVP increased cellular cAMP production in a dose-dependent manner. This was significantly blunted in the Na(+)-depleted cells (1 nM AVP; 481.9 vs. 341.0 fmol/micrograms protein; P less than 0.01). When cells were incubated with the Na(+)-depleted medium containing 25 mM NaHCO3, [Na+]i decreased promptly, but the pHi remained unchanged. Under this condition, the AVP-induced increase in cellular cAMP production was not altered (1 nM AVP; 390.9 vs. 334.8 fmol/micrograms protein). Also, after the Na(+)-depleted cells were incubated in 20 mM NH4Cl, which promptly normalized pHi despite the decreased [Na+]i, the response of cAMP production to AVP was restored. Amiloride (1 x 10(-5)-1 x 10(-3) M), which blocks the Na+/H+ exchange, decreased pHi and AVP- and forskolin-induced cAMP production in a dose-dependent manner. These results indicate that the decrease in [Na+]i promptly inhibits AVP-induced cAMP production mediated through the reduction in pHi in renal inner medullary collecting duct cells.
authors.affiliation: Department of Medicine, Jichi Medical School, Tochigi, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ishikawa
authors.forename: K
authors.initials: K
authors.lastname: Okada
authors.forename: T
authors.initials: T
authors.lastname: Saito
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis*; D006863:Hydrogen-Ion Concentration; D007679:Kidney Medulla / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*
chemical_list: D000643:Ammonium Chloride; D001127:Arginine Vasopressin; D005576:Colforsin; D000584:Amiloride; D012964:Sodium; D000242:Cyclic AMP