Effect of prostaglandin I2 on platelet adhesion.

The adherence of platelets to collagen fibrils was not affected by prostaglandin I2 (PGI2) applied in a wide concentration range (0.1-100 ng/ml). The retention of platelets on glass beads which includes adhesion as well as subsequent clumping of platelets was, however, greatly reduced at PGI2 concentrations higher than 0.5 ng/ml. The results suggest that PGI2 even at high concentration does not interfere with the primary process of platelet adhesion, i.e., with the formation of a monocellular platelet layer on collagen fibrils and artificial surfaces, but it inhibits clumping of further platelets to this layer and prevents subsequent platelet thrombus formation.