title: External ATP mimics carbachol in initiating calcium mobilization from pancreatic beta-cells conditioned by previous exposure to glucose.
abstract: 1 Exposure to ATP (2-200 microM) resulted in a prominent peak of 45Ca efflux, when beta-cell-rich pancreatic islets from ob/ob-mice were perifused with a Ca2+-deficient medium. ADP and the stable alpha/beta-methylene analogues of ATP and ADP also had stimulatory effects. 2 The nucleotide initiation of 45Ca efflux mimicked that obtained with carbachol both in requiring previous exposure to glucose and in being more pronounced after replacing extracellular Na+ by K+. 3 It was possible to induce repeated peaks of stimulated 45Ca efflux, when the exposure to ATP was interrupted with intervals of perifusion with glucose-containing media. 4 The observations are consistent with the existence of P2-purinoceptors in islets, suggesting that these receptors mediate a similar mobilization of calcium as noted when activating polyphosphoinositide breakdown with carbachol. In view of the high contents of ATP and ADP in the beta-cell secretory granules, activation of P2-purinoceptors should be considered as a possible mechanism for amplification of the initial insulin secretory response.
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002132:Calcium Radioisotopes; D002217:Carbachol / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D011976:Receptors, Muscarinic / Q000187:drug effects
chemical_list: D000227:Adenine Nucleotides; D002132:Calcium Radioisotopes; D007473:Ion Channels; D011976:Receptors, Muscarinic; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D002217:Carbachol; D005947:Glucose