Laboratory Investigations of Potential Heparin — Iloprost Interactions

Abstract

Prostacyclin, or PGI₂, is a powerful inhibitor of platelet aggregation, and has been used clinically to reduce platelet activity in thrombotic conditions. In addition to its anticoagulant effects, heparin also has a direct effect upon platelet function. Heparin increases platelet sensitivity to ADP and adrenaline, lowering the threshold concentrations of these agents which are required to induce aggregation [18]. Heparin has been reported to induce aggregation in washed platelets in the absence of standard agonists [4]. Inhibition of adenylate cyclase activity by heparin has been demonstrated in several biological systems, including rat hepatocytes [1], rat ovarian cell membranes [15], and human platelets [11]. Reduction of intraplatelet cyclic AMP may contribute to the enhancement of platelet aggregability by heparin.