INTERACTION OF THROMBIN WITH AiiTITHROMBIN III ANDt@ACROGLOBULIN IN THE PLASMA

riBSTRACT When diluted plasma or defibrinated plasma was incubated in the presence of CaC12, and the aliquot was mixed with S-2238 in the presence or absence of heparin, hydrolysis of S-2238 was initially smaller in the presence of heparin, but later (at 2 hr incubation) no difference was observed in the presence and absence of heparin. When diluted plasma or defibrinated plasma was incubated with thrombin, and at intervals the aliquot was mixed with S-2238 in the presence or absence of heparin, there was no difference in the extent of hydrolysis of S-2238 in the presence and absence of heparin. When diluted plasma was incubated with heparin and thrombin, and at intervals the aliquot was mixed with S-2238, the hydrolysis of S-2238 was larger in the absence of heparin than in its presence. When highly purified .&macroglobulin (&M) and antithrombin III (ATIII) were used, thrombin activity was initially enhanced, and quick inactivation of thrombin by ATIII was shown regardless of the presence of heparin. Protection of thrombin activity by x,M from inactivation by ATIU were observed to some extent. Electrophoresis shows that thrombin-ATIII complex formed quickly in the plasma in the presence of heparin, but little complex formation was shown in the absence of heparin. the addition of Ca++, In conclusion, thrombin generated by or thrombin added to the plasma seems to be easily inactivated by ATIII in the presence of heparin. Thrombin added to the plasma in the absence of heparin seems to be quickly entrapped by y,M.