Wound tensile strength in the hairless guinea pig following irradiation with pure ultraviolet-A light.

Ultraviolet light in the wavelength range of 315-400 nm (UVA) is known to penetrate the epidermis more readily than UVB and to result in significant dermal damage. Fibroblasts within the dermis are responsible for the production of collagen, which is the chief determinant of wound tensile strength during the third week of wound healing. The present study assesses the effects of UV radiation limited to the UVA wavelength on wound tensile strength in the hairless guinea pig. Twenty female hairless guinea pigs were randomly divided into two equal groups (n = 10). Group 1 animals served as controls. Group 2 animals were irradiated with 120 J/cm2 from a pure UVA fluorescent light source every other day for a period of 21.3 weeks (cumulative dose = 8960 J/cm2). Upon completion of the irradiation schedule, a standard 6 cm linear full-thickness surgical wound was created on the dorsum of all animals and allowed to heal for 21 days. The wounds were excised and wound tensile strength was assessed by determining breaking strength and dividing by the breaking-point surface area. Wound tensile strength was significantly lower (p less than 0.0017) in irradiated animals (0.99 +/- 0.12) than in controls (1.54 +/- 0.08). Therefore, UVA at this dose significantly decreased wound tensile strength in this model and raises further concern regarding exposure to this wavelength of ultraviolet radiation.