title: Beta-adrenergic regulation of H+ secretion by cultured outer medullary collecting duct cells.
abstract: The effects of the beta-adrenergic agonist isoproterenol (Iso) on cells of the inner stripe portion of the rabbit outer medullary collecting duct (OMCDi) grown in primary culture were examined using whole cell patch-clamp techniques and measurements of intracellular pH (pHi) and Ca2+. Iso (10(-6) M) increased the cellular Cl- conductance, and this effect was mimicked by treatment of the cells with dibutyryladenosine 3',5'-cyclic monophosphate (cAMP, 10(-5) M) or protein kinase A (PKA, 0.4 U/ml). Iso did not alter the baseline pHi, but it did increase the activity of both the Cl-/HCO3- antiporter and the H(+)-adenosinetriphosphatase (H(+)-ATPase). The increase in Cl-/HCO3- antiporter rate was mimicked by dibutyryl-cAMP plus 3-isobutyl-1-methylxanthine (cAMP + IBMX, 10(-4) M + 10(-5) M). However, the Iso-induced stimulation of the H(+)-ATPase activity was not mimicked by cAMP + IBMX. Measurements of intracellular Ca2+ showed that Iso also increased intracellular Ca2+ levels. This response was not dependent on extracellular Ca2+, nor did cAMP + IBMX appreciably alter intracellular Ca2+. Consequently, we postulate that beta-adrenergic agonists are potential stimulators of OMCDi H+ secretion. These agonists stimulate cellular HCO3- efflux through a signal transduction pathway involving cAMP and PKA. However, a different signal transduction pathway appears to mediate the stimulation of cellular H+ efflux. This second pathway may involve an elevation of intracellular Ca2+.
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002712:Chlorides / Q000502:physiology; D004594:Electrophysiology; D017506:H(+)-K(+)-Exchanging ATPase / Q000502:physiology; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D007679:Kidney Medulla; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D011494:Protein Kinases / Q000494:pharmacology; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000502:physiology*
chemical_list: D002712:Chlorides; D011943:Receptors, Adrenergic, beta; D003994:Bucladesine; D006859:Hydrogen; D011494:Protein Kinases; D017506:H(+)-K(+)-Exchanging ATPase; D007545:Isoproterenol; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine