Potentiation of Adrenaline-Induced Platelet Aggregation by Angiotensin II

Summary

The effects of angiotensin II (ANG II) alone and in combination with other agonists on human platelet aggregation, thromboxane B₂ (TxB₂) and cytosolic [Ca₂₊]i were investigated. ANG II (10^™11 - 10^™7 M) alone had no direct effect on aggregation, TxB₂ production or [Ca²⁺]i after short- (<2 min) or longterm (30 min) incubation. In contrast, low concentrations of ANG II (10^™11 M) enhanced adrenaline-induced platelet aggregation but high concentrations (10^™7 M) had an inhibitory effect. Moreover, ANG II (10^™11 - 10^™7 M) augmented platelet responses to the TxA₂ mimetic, U44069. Pretreatment of platelets with flurbiprofen abolished this facilitatory effect of ANG II on adrenaline- but not on U44069-induced platelet aggregation. These results suggest that ANG II stimulation of agonist-induced platelet activation may be due to potentiation of the effects rather than the synthesis of TxA₂

Keywords

Adrenaline - Angiotensin II - Thromboxane A₂ - Platelet aggregation

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