Efffct of Heparin-CI ina Complex on the Action of Kallikrein

CI INA has been known to show not only the inhibitory action on CI esterase, but also the inhibition of blood clotting factors including factor XI, factor XII, plasma kallikrein and plasmin. In this paper the authors attempt the following studies to elucidate the function of heparin-CI INA complex in the field of contact phase. By the addition of heparin into normal human plasma the pattern of cross immunoelectrophoresls of CI INA becomes to show three peaks indicating a complex formation of heparin. CI INA and other clotting factors, which is reversible to move to an original peak by the addition of Protamin sulfate. And it has been analysed that the first peak consists of a complex of heparin-CI INA complex with factors XI and XII and the second peak is a complex of heparin-CI INA and the third peak shows a complex of heparin-CI INA with kallikrein and plasmin. On the observation of inhibitory action of heparin-CI INA complex by the use of chromogenic substrate (S-2302) method for plasma kallikrein assay, it is conformed that the inhibitory action of CI INA on kallikrein is enhanced in parallel with the increasing amount of heparin added into the tested plasma, and the same tendency is observed on the experiment with AT-III free plasma. In conclusion it is strongly suggested that heparin-CI INA complex might be able to form a complest with kallikrein to inhibit its amidolytic activity more effectively than CI INA without heparin does.