gamma-Irradiation-induced mortality: protective effect of protease inhibitors in chickens and mice.

Chickens (Gallus domesticus) were protected from the acute gamma-irradiation-induced mortality (within 24 hours) by the proteolytic enzyme inhibitors, soy-bean trypsin inhibitor (SBTI), lima bean inhibitor (LBTI), antipain, alpha-N-benzoyl-L-arginine ethyl ester HCl (BAEE), trasylol, and leupeptin. Several other enzyme inhibitors, p-tosyl-L-arginine methyl ester HCl (TAME), alpha-tosyl-lysyl-chloromethyl ketone HCl (TLCK) and epsilon-amino caproic acid (EACA), did not protect. EACA even increased the mortality caused by gamma-irradiation. The pattern of protective enzyme inhibitors suggests involvement of a kallikrein-like enzyme. SBTI and antipain also protected against low range lethal gamma-irradiation exposures, 690 R in BALB/c and 880 R in SJL/J mice. It is suggested that enhanced vascular permeability, which in chickens is known to be the cause of the irradiation mortality during the first 24 hours, may also contribute to the mortality in mice during the first week after irradiation.