THE CALCIUM ION CHANNEL BLOCKER ISRADIPINE INHIBITS PLATELET ADHESION AND PLATELET THROMBUS FORMATION ON HUMAN VENOUS SUBENDOTHELIUM

In order to examine the effect of isradipine, a calcium antagonist of the dihydropyridine family, on the platelet vessel wall interaction, human sephanous vein subendothelium from patients (with or without regular isradipine therapy), undergoing venous surgery was exposed to citrated human blood ina Baumgartner perfusion chamber under arterial blood flow conditions. Platelet adhesion and platelets thrombus formation were morphormetrically quantified using the evaluation technique of Baumgartner. The vessels were perfused either with citrated blood taken from volunteers or hypertensives (not on therapy), or from hypertensives 30 minutes after the intake of the last 2.5mg isradipine either orally or in-vitro addition of 0.5, 1, and 5μg/ml. The source of the vessel did not influence thrombogenicity. The surface induced platelet adhesion and platelets thrombus formation both were significantly lower in experiments with blood from patients having adjusted isradipine or with in-vitro isradipine addition as compared to controlled and hypertensives without medication. As the vascular segments used were no longer able to produce any prostaglandin, the results in this perfusion model indicates a platelet-derived improvement in platelet vessel wall interaction by isradipine, which is not PGI₂- mediated.