Abstract
Summary
Whole body x-irradiation of mice, rats, and rabbits at the LD50 range increases the activity of certain tissue cathepsins. Liver, kidney, and intestine were the tissues tested, and it was found that one of 3 liver cathepsins, 2 of the same 3 cathepsins in kidney, and 2 of the 3 in intestine were increased in activity by the radiation. This appears due, at least in the case of rat kidney carboxypeptidase, to the destruction by the x-rays of an enzyme inhibitor. It is possible that the source of all inhibitor found in tissues and blood alike is the blood cell, probably the leukocyte. The possibility is suggested that the reduction of carboxypeptidase inhibitor in blood cells may serve as a basis for determining, within 24 hours of the exposure, whether or not an individual has received a lethal dose of ionizing radiation.
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