Indomethacin and ibuprofen inhibit the uptake of 45Ca2+ by washed human platelets through a thromboxane A2-independent mechanism.

Indomethacin and ibuprofen inhibited adrenaline- and calcium ionophore A23187-stimulated 45Ca2+ uptake by isolated human platelets in a concentration-dependent manner. Mediation of these effects by thromboxane A2 (TXA2) inhibition was discounted since under the same experimental conditions, adrenaline did not stimulate TXA2 synthesis and A23187-stimulated TXA2 synthesis was only marginally inhibited by concentrations of ibuprofen and indomethacin that inhibited 45Ca2+ uptake by 50%. These data indicate that the inhibitory action of non-steroidal anti-inflammatory drugs (NSAIDs) on platelet activity may be due, at least in part, to effects on calcium mobilisation at the plasma membrane level. The present results may also be of relevance to the anti-inflammatory action of NSAIDs.