Beta-adrenergic induced potassium current in Xenopus oocyte: involvement of cyclic AMP.
The effect of a beta-adrenergic agonist, on full-grown Xenopus oocytes, still surrounded by their ovarian envelopes, has been studied by electrophysiological methods. The oocytes were hyperpolarized by isoproterenol. Under voltage clamp, the elicited outward current reversed at a membrane potential of - 95 mV, a value close to the K+ equilibrium potential. The isoproterenol induced current varied linearly with the membrane potential in the range studied (- 120 mV, - 30 mV). Half-maximum current was obtained at 3.10(-8) M isoproterenol. Propranolol (10(-7) M) completely suppressed the response to isoproterenol (10(-9) to 10(-5) M). 8-Br-cAMP induced a current which also reversed at - 95 mV. Methyl-isobutyl-xanthine (MIX), a potent inhibitor of phosphodiesterases, potentiated the current induced by isoproterenol. These experiments strongly suggest that the increase in K+ permeability due to catecholamines is mediated by cAMP.
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism*; D005260:Female; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D014981:Xenopus
D015124:8-Bromo Cyclic Adenosine Monophosphate; D000242:Cyclic AMP; D007545:Isoproterenol; D000109:Acetylcholine; D011188:Potassium; D015056:1-Methyl-3-isobutylxanthine