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.