Enzymatic Changes in Beta-Irradiated Epidermis of Guinea Pigs: I. Free and Inhibitor-Bound Ribonuclease

Abstract

After irradiation of the skin of guinea pigs with a single surface dose of 3000 rep of BETA -radiation from an Sr/sup 90/--Y/sup 90/ sealed source, there was a progressive increase in epidermal RNase activity (pH 7.7) which by the second week reached a peak about three times the control value. Depending on the method of preparation of tissue for assay, a significant increment in activity was observed as early as the first day or not later than the sixth day after irradiation. During this interval there were no grossly visible signs of injury. Microscopically, however, various alterations were readily seen, and the progressive rise in enzymatic activity paralleled the increase in dead and dying cells. After thin strips of peeled irradiated tissue were washed prior to homogenization, a progressive increase in RNase activity was observed in the wash, suggesting leakage of enzyme from damaged cells.This increase could be accounted for, at least in part, by a decrease in inhibitor-bound RNase (i-RNase) in the irradiated tissue. The threshold dose for inducing increased RNase activity was about 600 rep of Beta-radiation. It si suggested that the observed rise in enzymatic activity constitutes a phase of the general response of cells tomore » injury, may initiate the autolytic process which releases the enzymes or destroys their inhibitors.« less