ISRADIPINE DECREASES ARTERIAL THROMBOGENICITY IN RABBITS - A MORPHOMETRIC AND RADIOISOTOPIC STUDY

The effect of isradipine, a calcium antagonist, on aortic and iliac wa ll thrombogenicity was examined in rabbits. After one week of dosing, the abdominal aortic and iliac artery endothelium was abraded using a Fogarthy catheter; One group of animals (n=8) was dosed for one week w ith isradipine 0.3 mg/kg. A second group of animals received 10 mg ace tylsalicylic acid (ASA)/kg daily in addition, while a third group rece ived the vehicle only. Finally, a fourth group of animals (n=8) was tr eated with ASA only. The percentage denuded surface covered with conta ct (unspread) platelets decreased significantly (p<0.01) from 14.7+/- 2.0 to 9.3+/-2.1 (6.2+/-0.8 to 3.7+/-0.4*). The amount of contact and spread platelets was diminished from 84.9+/-5.6 to 71.4+/-4.4 (91.8/-5.3 to 75.2+/-4.6). Platelet thrombi decreased from 7.4+/-0.9 to 4. 6+/-1.4 (9.4+/-1.9 to 5.2+/-0.7*) in the aortic and the iliac artery, respectively. In-111-platelet deposition decreased by 39.9 and 41.9%. Concomitant ASA -therapy not only abolished the effect of isradipine but enhanced thrombogenicity, probably as a result of almost complete blockade of vascular PGI(2)-production.