title: Evidence for presence of functional beta-adrenoceptor in rabbit S2 proximal straight tubules.
abstract: The effect of isoproterenol on the electrophysiological properties of the S2 proximal segment of the rabbit was examined. Isoproterenol at 10(-8) to 10(-4) M depolarized the basolateral membrane voltage (Vb) in a dose-dependent manner. Propranolol attenuated the isoproterenol-induced depolarization. These possible mechanisms of cell depolarization were explored. The role of luminal Na(+)-organic solute cotransport was negligible, since the removal of organic solute did not change the depolarization. Basolateral Na(+)-(HCO3-) cotransport was supported by the finding that 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid inhibited isoproterenol-induced depolarization. Basolateral K+ conductance was suggested by the finding that the application of Ba2+ blocked the isoproterenol-induced depolarization. Na(+)-K(+)-adenosine-triphosphatase (ATPase) was questionable. Although ouabain blocked isoproterenol-induced depolarization, the removal of Na+ did not inhibit the depolarization. Further experiment revealed that dibutylyl-adenosine 3',5'-cyclic monophosphate (cAMP), 8-bromo cAMP, and forskolin did not mimic the response of isoproterenol. These results demonstrate: 1) there is a functional beta-adrenoceptor that depolarizes Vb; 2) isoproterenol-induced depolarization is due to an inhibition of basolateral K+ channel or the activation of basolateral Na(+)-(HCO3-)n cotransport; 3) isoproteronol-induced depolarization is independent of cAMP in the rabbit proximal tubule.
authors.affiliation: Department of Clinical Biology and Hormonal Regulation, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kudo
authors.forename: Y
authors.initials: Y
authors.lastname: Kondo
authors.forename: K
authors.initials: K
authors.lastname: Abe
authors.forename: Y
authors.initials: Y
authors.lastname: Igarashi
authors.forename: K
authors.initials: K
authors.lastname: Tada
authors.forename: K
authors.initials: K
authors.lastname: Yoshinaga
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D004594:Electrophysiology / Q000379:methods; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D005260:Female; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D010477:Perfusion; D011188:Potassium / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology*; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D027982:Sodium-Bicarbonate Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D011943:Receptors, Adrenergic, beta; D027982:Sodium-Bicarbonate Symporters; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D001464:Barium; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D003994:Bucladesine; D012964:Sodium; D011433:Propranolol; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase; D007545:Isoproterenol; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium; D002118:Calcium