ACTION SPECTRUM FOR UV-INDUCED LIPID-PEROXIDATION IN CULTURED HUMAN SKIN FIBROBLASTS

Lipid peroxidation was measured by release of thiobarbituric acid-reactive substances (TBARS) into the supernatant of cultured human skin fibroblasts. This process is triggered by ultraviolet A (UVA) and ultraviolet B (UVB) radiations. For UVA irradiances and irradiation times up to 40 W . m(-2) and 90 min, respectively, the peroxidation response is linear and obeys the reciprocity law. Corresponding values for UVB are 12 W . m(-2) and 30 min, respectively. The action spectrum of the peroxidation process shows a continuously increasing response from about 425 to 275 nm. Whereas the UVB to UVA effectiveness ratio lies in the range of 10(3) to 10(4) for most in vitro or in vivo UV-induced responses, the ratio is only 10 to 100 for the peroxidation process. Given the solar spectral distribution, solar UVA radiation is by far the most effective in triggering the peroxidation response.