Comparison of the inhibitory effects of aspirin and ticlopidine on platelet aggregation and Ca2+ mobilization in rat platelets.

To study the cause of the sex difference in the inhibitory effects of aspirin on platelet functions, we compared the effects of aspirin and ticlopidine in rat platelets. Aspirin showed the sex difference in the effects on the collagen-induced platelet aggregation and the malondialdehyde (MDA) production, but ticlopidine showed no sex difference in the effects on those. The C-AMP level in male rat platelets was the same as that in female rat platelets. Ticlopidine increased the C-AMP level in rat platelets, but aspirin did not. Aspirin suppressed the intracellular Ca2+ mobilization in male rat platelets more strongly than in female rat platelets. Ticlopidine suppressed the Ca2+ mobilization in both sexes equivalently. The above results suggest that the sex difference in the inhibitory effects of aspirin on rat platelet functions comes from the sex difference in the thromboxane (TX) production in rat platelets.