Interaction between Endogenous Proteases and Plasma Protease Inhibitors in vitro and in vivo

Abstract

The protease inhibitors of plasma have usually been estimated from the residual tryptic activity after addition of trypsin in excess of the protease inhibiting capacity. The specificity of the individual plasma protease inhibitors has been assessed after separation of plasma by starch or agarose gel electrophoresis with the aid of fibrin agar plates [1] or from the effect of addition of purified inhibitors on enzyme activity. But such procedures produce information of only limited biologic interest because they teach nothing about the relative affinity of the various inhibitors. Of much greater biologic interest is the fate of protease released in the natural excess of inhibitors occurring in plasma and intercellular fluid. Their fate must be a function of the concentration and relative affinity of the enzymes for the inhibitors. In vitro experiments may warrant certain conclusions, provided that the concentrations of the inhibitors in the tissue fluids, their relative affinity for the protease and the rate of elimination of the complexes are taken in account.

Supported by grants from the Swedish Medical Research Council (Project No. B74- 17X-3910-02A) and the Torsten and Ragnar Söderbergs Funds.