title: Activation of protein kinase C by a tumor-promoting phorbol ester in pancreatic islets.
abstract: Rat pancreatic islet homogenates display protein kinase C activity. This phospholipid-dependent and calcium-sensitive enzyme is activated by diacylglycerol or the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). In the presence of TPA, the Ka for Ca2+ is close to 5 microM. TPA does not affect phosphoinositide turnover but stimulates [32P]- and [3H]choline-labelling of phosphatidylcholine in intact islets. Exogenous phospholipase C stimulates insulin release, in a sustained and glucose-independent fashion. The secretory response to phospholipase C persists in media deprived of CaCl2. It is proposed that protein kinase C participates in the coupling of stimulus recognition to insulin release evoked by TPA, phospholipase C and, possibly, those secretatogues causing phosphoinositide breakdown in pancreatic islets.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002794:Choline / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology*; D010704:Phorbols / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010761:Phosphorus Radioisotopes / Q000378:metabolism; D011493:Protein Kinase C; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000494:pharmacology
chemical_list: D004075:Diglycerides; D007328:Insulin; D010704:Phorbols; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D010761:Phosphorus Radioisotopes; D011494:Protein Kinases; D011493:Protein Kinase C; D010738:Type C Phospholipases; D002794:Choline; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; C013965:diolein