ULTRAVIOLET-A INDUCED DELAYED WOUND CONTRACTION AND DECREASED COLLAGEN CONTENT IN HEALING WOUNDS AND IMPLANT CAPSULES

Chronic exposure to ultraviolet-A radiation causes changes in the bioc hemistry of dermal connective tissue. To investigate its effects on wo und healing, we irradiated Sprague-Dawley rats for 4 months using a bl ack ray ultraviolet-A radiation source (560 J/cm2). Full thickness ski n wounds of 2 cm in diameter were then created on the back of each ani mal and silicone cubes were implanted subcutaneously into the irradiat ed area of the back. Wound contraction in the irradiated animals (n = 28) was significantly slower than that of the controls (n = 29) (p < 0 .001). Postoperatively, the hydroxyproline content of the contracted w ounds and the implant capsules was assessed at 6 and 12 weeks, respect ively. In the irradiated animals, it was found to be significantly les s than that of the controls (p < 0.001). A delay in wound contraction and a decrease in hydroxyproline content of healing wounds and implant capsules, reflecting an alteration in collagen metabolism, are two ef fects of prolonged intermittent ultraviolet-A radiation pretreatment.