COMPARATIVE-STUDIES OF GLYCOPROTEIN IB IN HEPARIN-COATED AND NONHEPARIN COATED EXTRACORPOREAL-CIRCULATION CIRCUITS

Contact between blood and artificial materials has various effects on blood. Impairment of platelet function is an especially important and well known effect, but its precise mechanism is not clearly understood . The authors constructed a circulation model to investigate the effec t of extracorporeal circulation on platelet membrane glycoproteins (CP s), especially GP Ib, and to compare the changes in CP Ib in heparin c oated (group C) and nonheparin coated (group N) circuits. As determine d by flow cytometry, CP Ib in both groups decreased on initiating circ ulation, but the decrease in group N was significantly larger than tha t in group C. There was no observed change in GP IIb/IIIa levels in ei ther group. The extent of shear stress induced platelet aggregation si gnificantly decreased during circulation in both groups. Decreases in the extent of shear stress induced platelet aggregation were significa ntly less with the use of heparin coated circuits. In addition, the am ount of CP Ib in the high speed pellet decreased progressively during circulation in both groups. In contrast, the amount of GP Ib in the Tr iton insoluble (low speed) pellet increased dramatically during circul ation. However, expression of CP Ib in the Triton soluble platelet fra ction was low in both groups. From the results, it was concluded that the cause of the decrease in platelet function during extracorporeal c irculation is attributable to the internalization of CP Ib from the pl atelet surface inside the platelet. It also can be said that a heparin coated circuit is one effective means of controlling this change.