Separation of the Antihemophilic Factor (F. VIII) from Fibrinogen With Thrombin and Manganese Chloride. ∗

Discussion and Summary

These experiments show that the AHF activity of plasma is enhanced by dialysis, especially against MnCl₂, and that thrombic destruction of AHF can be prevented by prior dialysis of plasma against MnCl₂. Manganese chloride is clearly the most effective cation tested with respect to protection of AHF against thrombic destruction and 0.02 M is the optimal concentration. Manganese does not protect AHF, however, by destroying thrombin or by altering the thrombin destroying properties of antithrombin. This specific effect of Mn++ in protecting AHF is not surprising because others have observed that Mn++ both activates and stabilizes AHF in plasma (11,12). Our experiments suggest that the protective action of MnCl₂ may be related in some manner to changes induced in the AHF molecule. The nature of any such change remains to be clarified.

Identification of the AHF activity in the treated plasmas was established by injection into both normal and hemophilia dogs. These experiments showed that the AHF activity observed in vitro could also be observed in vivo. Normal dogs circulated somewhat more and hemophilic dogs somewhat less AHF than expected. It is suggested by these results and a similar result using MnCl₂ alone that AHF may become “activated” by Mn++ in vivo in normal but not hemophilic animals. This apparent “activation” may, however, be nothing more than an indirect method of producing the well known “adrenaline effect.”