1 The direct overall metabolic effects of calcium entry blockers on human platelets were evaluated using a sensitive microcalorimetric method.
2 The effect on platelet metabolism of four calcium entry blockers with different profiles of action was examined and compared with the relaxant response on human cerebral vessels in vitro.
3 Diltiazem (10 -8, 10-4 M) and nifedipine (10-10, 10-6M) were without effect on overall platelet metabolism. On the other hand flunarizine (10-4M) and verapamil (10-4M) significantly reduced metabolism, while lower concentrations of these agents did not change heat production.
4 The thermogenic response occurred at concentrations of the calcium entry blockers that were much higher than those observed during therapy and the concentrations which relax human cerebral arteries in vitro.
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