Cl- currents activated via purinergic receptors in Xenopus follicles.
Ionic currents elicited via purinergic receptors located in the membrane of Xenopus follicles were studied using electrophysiological techniques. Follicles responded to ATP-activating inward currents with a fast time course (F(in)). In Ringer solution, reversal potential (Erev) of F(in) was -22 mV, which did not change with external substitutions of Na- or K+, whereas solutions containing 50 or 5% of normal Cl- concentration shifted Erev to about +4 and +60 mV, respectively, and decreased F(in) amplitude, indicating that F(in) was carried by Cl-.F(in) had an onset delay of approximately 400 ms, measured by application of a brief jet of ATP from a micropipette positioned near the follicle (50 microns). F(in) was inhibited by 50% in follicles pretreated with pertussis toxin. This suggests a G protein-mediated receptor channel pathway. F(in) was mimicked by 2-MeSATP and UTP, the potency order (half-maximal effective concentration) was 2-MeSATP (194 nM) > UTP (454 nM) > ATP (1,086 nM). All agonists generated Cl- currents and displayed cross-inhibition on the others. F(in) activation by acetylcholine also cross-inhibited F(in)-ATP responses, suggesting that all act on a common channel-activation pathway.
Arellano
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Centro de Neurobiología, Universidad Nacional Autónoma de México, Queretaro, Mexico.
Garay
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Miledi
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D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D018118:Chloride Channels / Q000502:physiology*; D004594:Electrophysiology; D005260:Female; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D006080:Ovarian Follicle / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology; D011983:Receptors, Purinergic / Q000502:physiology*; D014544:Uridine Triphosphate / Q000494:pharmacology; D014982:Xenopus laevis
D018118:Chloride Channels; D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; C074644:uridine triphosphate receptors; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D014544:Uridine Triphosphate