Generation of a PGI2-like activity by deendothelialized rat aorta.

We have tested a platelet aggregation inhibitor in the incubation fluid of deendothelialized fragments of the rat aorta and compared it with that of "intact" fragments. Some of the properties of the aortic inhibitor, and its effects on platelet adhesion to collagen fibrils, on platelet factor-3 (PF-3) availability, and on the activated partial thromboplastin time (APTT) and thrombin time (TT) were also evaluated in comparison with similar effects exerted by PGI2. We found that the incubation fluid of deendothelialized aortic samples contained inhibitor activity comparable with that of "intact" samples. The aortic inhibitor had similar properties to PGI2. The aortic inhibitor and PGI2 slightly inhibited light transmission changes of EDTA-PRP following exposure to collagen. However, scanning electron microscopy showed no appreciable difference in platelet adhesion to collagen fibrils. PGI2 and the aortic inhibitor inhibited Kaolin-induced PF-3 availability, but did not prolong the APTT or TT.