HYDROGEN-PEROXIDE AND CATALASE IN UVA-INDUCED LIPID-PEROXIDATION IN CULTURED FIBROBLASTS

UVA-induced lipid peroxidation in cultured human skin fibroblasts, as measured by the release in the supernatant of thiobarbituric acid-reac tive substances, is found to be linear with increasing irradiation dos e (up to about 250 kJ m(-2)), Concomitantly, within this dose range ca talase is strongly inactivated by UVA radiation according to an expone ntial process (k approximate to 0.01 kJ(-1) m(2)). This suggests that catalase is not involved in modulating the peroxidation process, Inact ivation of catalase by 3-amino-1,2,4-triazole can be efficiently achie ved prior to irradiation, This inactivation has no consequence on the extent of peroxidation triggered by subsequent exposure to UVA radiati on, It may be therefore strongly suggested that catalase is not, via H 2O2 removal, a key enzyme in the cellular defence equipment towards UV A-peroxidative stress, An alternative interpretation may be formulated which supports the view that H2O2 produced upon exposure to UVA has n o or very little role in triggering the lipid peroxidation process.