Radiation and Wound Healing: A Study of the Role of Sulfur Amino Acids

Abstract

Total-body exposure to ionizing radiation has been reported to retard the healing of wounds (1-4). Since wounds heal by an innate physiological process which involves the reaction of the entire body to trauma, the healing delay might be expected to be due to the extensive metabolic disturbances produced by whole-body irradiation. However, the slower healing apparently is not entirely due to this gross physiological disturbance. Locally applied radiation has been found to retard significantly the gain in tensile strength (5, 6), and increasing the dose of radiation progressively inhibits growth of cultured fibroblasts (7-9). In any case, the delayed response is not clearly understood. Only relatively recently has attention been focused on the biochemistry of wounds and wound healing. Methionine or cystine administered either in the diet or parenterally has been found to increase significantly the rate of healing of experimental wounds in nonirradiated animals (10-12), but other amino acids have been found to have little or no effect. Recently there have been reports by Russian investigators that 1100 R of ionizing radiation causes a sharp drop in incorporation of S35methionine into the bone marrow, spleen, and skeletal muscle of rabbits (13) and that doses of radiation as low as 50 R strongly depress the incorporation rate of C14-methionine into calcified tissues of rats (14). Available evidence suggests, therefore that radiation exposure causes an alteration in methionine metabolism and that this alteration in turn may be responsible for impaired wound healing.