EFFECTS OF ULTRAVIOLET-A AND ANTIOXIDANT DEFENSE IN CULTURED FIBROBLASTS AND KERATINOCYTES

Lipid peroxidation, measured by the thiobarbituric acid-reactive subst ances assay, was evaluated for cultured human skin fibroblasts and ker atinocytes exposed to ultraviolet A radiation (320-400 nm, UVA). Perox idation increases with increasing UVA doses and is much lower for kera tinocytes than for fibroblasts. Immediate UVA-induced cytotoxicity, mo nitored by the trypan blue exclusion assay, is also lower for keratino cytes. Thus, cultured human skin keratinocytes are less sensitive than fibroblasts to the immediate deleterious effects of UVA with respect to membrane damage and lipid peroxidation. As a first attempt to under stand this lower sensitivity of keratinocytes, basal levels of antioxi dant defenses including total glutathione, superoxide dismutase, gluta thione peroxidase and catalase were evaluated in both keratinocytes an d fibroblasts from the same donors. We failed to correlate this lower susceptibility of keratinocyte to UVA-induced lipid peroxidation and c ytotocixity with a higher antioxidant status.