Enzymic Processes and Vascular Changes in the Skin Radiation Reaction

Abstract

Factors influencing the early phase of the inflammatory reaction occurring within minutes after irradiation have been studied. This phase is important as it affects the whole subsequent course of the radiation reaction. The capillary permeability changes were estimated by measurement of the leakage of a vital dye injected into the experimental animals immediately after irradiation. The effect of different enzyme systems and their inhibitors on this phase of the radiation-induced inflammatory reaction were studied. While histamine and 5-hydroxytryptamine do not play a significant role (absence of modification of the response by mepyramine maleate or lysergic acid diethylamide), the participation of a protease system (diminution or abolition of response following soya bean trypsin inhibitor or epsilon-amino-n-caproic acid administration) was established. The action of the latter indicates the participation of lysosomal derivatives in the sequence of events leading to increased permeability. The degree of diminution of capillary permeability or its abolition by these inhibitors was tabulated and compared with the effects of compounds with a “desludging” or vasodilating effect on vessels (meso-inositol-hexanicotinate-Hexopal) and a substance which reduces capillary fragility (tri-hydroxyethyl-rutoside—“Factor P” Zyma.) The mechanism of action of these compounds and the interrelationship between the early impact of ionising radiations on the tissue catalytic systems and extracellular tissue events following irradiation are discussed.