title: Lack of evidence for voltage dependent calcium channels on platelets.
abstract: Intracellular calcium was measured in human platelets using the fluorescent calcium indicator Quin 2. A concentration dependent increase was observed with thrombin. Depolarisation induced by high KCl concentrations did not alter [Ca++]i. The calcium agonist Bay K 8644 did not affect resting levels or thrombin stimulated elevation of intracellular calcium. The calcium antagonists diltiazem, verapamil and PN 200-110 did not inhibit the thrombin stimulated elevation in [Ca++]i. Pretreatment of platelets with adenylate cyclase stimulants reduced the rate and magnitude of the maximal [Ca++]i elevation due to thrombin. In addition, thrombin stimulation of 45Ca++ influx was insensitive to Bay K 8644, verapamil, diltiazem and Pn 200-110. We conclude that functional voltage sensitive calcium channels are not present on human platelets.
authors.forename: V M
authors.initials: VM
authors.lastname: Doyle
authors.forename: U T
authors.initials: UT
authors.lastname: Rüegg
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000634:Aminoquinolines; D001792:Blood Platelets / Q000032:analysis* / Q000187:drug effects; D002118:Calcium / Q000097:blood*; D004110:Diltiazem / Q000494:pharmacology; D006801:Humans; D007473:Ion Channels / Q000032:analysis*; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000634:Aminoquinolines; D007473:Ion Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D012964:Sodium; D013917:Thrombin; D004110:Diltiazem; D009543:Nifedipine; C035739:Quin2; D002118:Calcium