Inhibitory effect of immobilized microsomal proteins on platelet aggregation

Bovine aorta microsome was solubilized by 0.5% Triton X-100, and then immobilized on agarose gel (Sepharose 4B). Immobilized microsomal proteins (I-MP) inhibited platelet aggregations induced by ADP, arachidonic acid, collagen, and thrombin. The decrease of free platelet count in sheared whole blood was suppressed by I-MP. The anti-aggregatory activity of I-MP on arachidonic acid-induced aggregation was inhibited by 15-HPETE. This result suggests that I-MP contains PGI2 synthetase activity. It is considered that immobilization of enzymatic systems in aorta microsome which limited platelet aggregation is effective to provide an antithrombogenicity to the artificial polymers for artificial organs, especially used under the conditions which frequently induced platelet aggregation.