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

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Abstract
After irradiation of the skin guinea pigs with a single surface dose of 3000 rep of [beta]-radiation from an Sr90-Y90 sealed source, there was a progressive increase in epidermal RNase activity (pH 7.7) which by the 2nd week reached a peak about 3 times the control value. A significant increment in activity was observed as early as the 1st day. Microscopically, 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 is suggested that the observed rise in enzymatic activity constitutes a phase of the general response of cells to injury. Radiation, like other types of injury, may initiate the auto-lytic process (es) which release (s) the enzymes or destroy (s) their inhibitor (s).