Different effector mechanisms for ATP and adenosine hyperpolarization in the guinea-pig taenia coli.
The hyperpolarizations in response to ATP and adenosine in the guinea-pig taenia coli, measured by the sucrose-gap technique at room temperature, were compared in solutions of modified ionic composition. ATP hyperpolarization was increased in low chloride and in low potassium, but was reduced to 12% of control in calcium-free solution on second application of the agonist. The response to adenosine, however, was decreased in low chloride, unchanged in low potassium and was 45% of control in calcium-free solution. The different mechanisms for ATP and adenosine hyperpolarization provide evidence for the presence of separate receptors.
D000241:Adenosine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D003106:Colon / Q000187:drug effects; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000378:metabolism; D011983:Receptors, Purinergic
D002712:Chlorides; D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate; D000241:Adenosine; D011188:Potassium; D002118:Calcium