γ‐Thrombin‐induced phospholipase A2 activation in rabbit platelets: Comparison with α‐thrombin

Abstract
γ‐Thrombin stimulated release of [3H]arachidonic acid ([3H]AA) accompanied by a significant production of PAF and lyso‐PAF by rabbit platelets. These responses, which reflect PLA2 activation, were observed after a prolonged lag and to a lower extent when compared to those induced by α‐thrombin which evoked a much higher elevation in intracellular calcium. This elevation together with [3H]AA release were markedly reduced by EDTA. However, addition of ionophore A23187 enhanced the release of [3H]AA by γ‐thrombin to the levels similar to those of α‐thrombin. We conclude that γ‐thrombin is able to activate PLA2 and suggest that calcium influx may be a limiting factor for this activation.

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