title: Calcium transients in human platelets monitored by aequorin, fura-2 and quin-2: effects of protein kinase C activation and inhibition.
abstract: Tumour-promoting phorbol esters and 1,2-dioctanoyl-sn-glycerol both induce calcium transients in platelets. However, these can only be detected in platelets loaded with aequorin, but not in those loaded with the fluorescent probes quin-2 and fura-2 presumably because of intracellular calcium buffering. Several effects induced by phorbol esters and diacylglycerols, including the rise in (Ca2+)i, the stimulation of Na+/H+ transporter and the inhibition of the effects of thrombin alone on (Ca2+)i are potently antagonised by staurosporine, a compound known to inhibit protein kinase C. Higher concentrations of staurosporine themselves inhibit the thrombin-induced calcium transient. Staurosporine inhibits the effects of phorbol esters and dioctanoyl glycerol with equal potency although the latter does not cause enzyme translocation of cytosolic protein kinase C to membranes. These results therefore suggest that some, if not all, the effects of protein kinase C activation can occur without translocation of the enzyme.
mesh_terms: D000331:Aequorin; D000470:Alkaloids / Q000494:pharmacology; D000634:Aminoquinolines; D001572:Benzofurans; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D007700:Kinetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000097:blood*; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D000634:Aminoquinolines; D001572:Benzofurans; D004075:Diglycerides; D005456:Fluorescent Dyes; C044295:1,2-dioctanoylglycerol; D000331:Aequorin; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate; C035739:Quin2; D002118:Calcium; D016257:Fura-2