SummaryThe cold promoted activation of factor VII occurs in parallel with an activation of a plasma arginine esterase, and, on inhibition of the cold activation of factor VII, the esterase activation also decreased. The inhibitor pattern supported our theory that the arginine esterase that is activated in the cold activation of factor VII is plasma kallikrein.The cold activation of factor VII was completely inhibited with soya bean trypsin inhibitor in doses that did not interfere with the contact activation. On the other hand, inhibition of the contact activation with hexadimethrine bromide did not interfere with the cold activation of factor VII except when this was kaolin induced. Contact and cold activation therefore appear to represent two different pathways for the activation of factor VII. The cold activation reaction is probably mediated by the activation of plasma prekallikrein, and inhibition of the plasma kallikrein activity correlates with the inhibition of the cold promoted activation of factor VII.
