A DOSE-RELATED CURVE OF WOUND TENSILE-STRENGTH FOLLOWING ULTRAVIOLET-IRRADIATION IN THE HAIRLESS GUINEA-PIG

A dose-related curve of wound tensile strength was derived following exposure to three doses of predominantly UVA (Ultraviolet A) radiation (98.3% between 315 nm and 400 nm, 1.7% < 315 nm). Forty female hairless guinea pigs were divided into four equal groups: Group 1 (controls); Group 2 (40 J[Joules]/cm2/day); Group 3 (80 J/cm2); and Group 4 (160 J/cm2). Preoperatively, the experimental groups were irradiated on alternate days for 16 weeks. Serial dorsal punch biopsies (4 mm) were taken prior to the initial exposure and subsequently at 2, 4, 8, 12, and 16 weeks and examined histologically and microscopically. Then, standard 6 cm midline dorsal surgical wounds were made and allowed to heal for 21 days. Wounds were excised and wound tensile strength was assessed. Significant decreases (p < .05) were noted in wound tensile strength of Groups 2, 3, and 4 compared to the controls, with the decrease being directly related to the dose received. Dermal changes were noted in all irradiated groups as early as four weeks after initial UVA/B exposure. Electron microscopy revealed elastosis and disruption of collagen fibers. Prolonged exposure to radiation, predominantly in the UVA range, appears to impede wound healing in a dose-related fashion and elicits elastosis and collagen disruption.