Lack of evidence for voltage dependent calcium channels on platelets |
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Authors: | V M Doyle U T Rüegg |
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Affiliation: | Preclinical Research, Sandoz Ltd., 4002 Basle, Switzerland |
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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. |
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