PLATELET EICOSANOIDS AND THE EFFECT OF CAPTOPRIL IN BLOOD-PRESSURE REGULATION

We investigated the eicosanoid synthesis of platelets of Wistar and of Okamoto spontaneously hypertensive rats (SHR), and the effect of capt opril in vitro, using [C-14]arachidonic acid as a tracer substrate and chromatographic determination. Lipoxygenase activity was elevated, wh ile the formation of cyclooxygenase products was reduced in SHR platel ets, compared to those of Wistar rats. This difference might play a ro le in the pathomechanism of hypertension in SHR. In SHR with lower blo od pressure, captopril reduced thromboxane synthesis, while in SHR wit h higher blood pressure thromboxane synthesis was unchanged, but the s ynthesis of prostaglandin D-2, a potent vasodilator, and of 12-L-hydro xy-5,8,10-heptadecatrienoic acid, a stimulator of endothelial prostacy clin formation, was increased. We may conclude that, in spite of the m issing angiotensin converting enzyme in platelets, a direct effect on platelet eicosanoid synthesis could contribute to the blood pressure d ecreasing effect of captopril. (C) 1997 Elsevier Science B.V.