Adenosine-induced slow ionic currents in the Xenopus oocyte.
Adenosine and its 5'-phosphorylated congeners evoke specific membrane-mediated responses in excitable tissues. Available data suggest that inhibition of the target cell occurs due to hyperpolarization, and in some preparations a compound effect of ATP (excitation and inhibition) has been found. However, the ionic mechanism of the purinergic-mediated response has not been studied by standard intracellular voltage-clamping techniques. Recently, we have discovered purinergic receptors in the Xenopus oocyte, a well defined giant cell amenable to rigorous electrophysiological and biochemical studies. We report here that in these cells, adenosine-induced slow membrane responses consisted of an early depolarizing (D) transient current carried by Cl ions, followed by a steady hyperpolarizing (H) current involving K+ ions. The relative potency sequence for the D current was ATP congruent to ADP greater than AMP congruent to adenosine; this order was reversed for the H current.
D000241:Adenosine / Q000494:pharmacology*; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002712:Chlorides / Q000378:metabolism; D005260:Female; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects*; D009865:Oocytes / Q000187:drug effects*; D010063:Ovum / Q000187:drug effects*; D011188:Potassium / Q000378:metabolism*; D013806:Theophylline / Q000494:pharmacology; D014982:Xenopus laevis
D002712:Chlorides; D007473:Ion Channels; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D013806:Theophylline; D000241:Adenosine; D011188:Potassium