Effect of Whole Body X-Irradiation on a Natural Inhibitor of Carboxypeptidase.

Abstract

The activity of 3 specific cathepsins in mouse liver, kidney, and intestine, as well as catheptic activity with hemoglobin as substrate was detd. after whole body X-irradiation at the LD50 level. X-irradiation increased the activity of one of the liver cathepsins, two of the kidney cathepsins, and two of those in the intestine. In no case was the activity toward hemoglobin affected. The activations noted are due, at least in the case of kidney carboxypeptidase, to destruction of an inhibitor carried probably in the leukocyte. The inhibitor level in the blood cells is reduced in various spp. by the same dose of radiation (about 400 r), regardless of their sensitivity to radiation lethality. It is suggested that this may serve as a clinical indicator of whether or not an individual human has received a lethal dose of radiation, within 24 hrs. of the exposure.