Phosphoinositide phosphorylation and hydrolysis in pancreatic islet cell membrane.
Membranes were isolated from dispersed rat pancreatic islet cells by attachment to Sephadex beads. When these membranes were exposed to [gamma-32P]ATP, formation of 32P-labeled phosphatidate, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate was observed. Carbamylcholine, added 10 s prior to lipid extraction, caused a dose-related fall in 32P-labeled phospholipids. The effect of the cholinergic agent was suppressed by atropine, ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid, and verapamil, and simulated, in part, by an increase in Ca2+ concentration. When the membranes were derived from islet cells prelabeled with [U-14C]arachidonate, carbamylcholine stimulation, in addition to decreasing labeled polyphosphoinositides, was accompanied by an increased production of labeled diacylglycerol, without a concomitant increase in labeled phosphatidylinositol. These results indicate that activation of a plasma membrane-associated phospholipase C directed against polyphosphoinositides represents a primary event in the functional response of the pancreatic beta cell to cholinergic agents.
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002250:Carbon Radioisotopes; D002462:Cell Membrane / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D006868:Hydrolysis; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000378:metabolism*; D008563:Membrane Lipids / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D051381:Rats; D014700:Verapamil / Q000494:pharmacology
D001095:Arachidonic Acids; D002250:Carbon Radioisotopes; D008563:Membrane Lipids; D010716:Phosphatidylinositols; D010761:Phosphorus Radioisotopes; D016718:Arachidonic Acid; D004533:Egtazic Acid; D001285:Atropine; D002217:Carbachol; D014700:Verapamil; D002118:Calcium