PHYSIOLOGICAL DOSES OF ULTRAVIOLET-IRRADIATION INDUCE DNA STRAND BREAKS IN CULTURED HUMAN MELANOCYTES, AS DETECTED BY MEANS OF AN IMMUNOCHEMICAL ASSAY

An immunochemical assay, i.e. sandwich enzyme-linked immunosorbent ass ay, has been modified to detect UV-induced damage in cellular DNA of m onolayer-grown human melanocytes, The method is based on the binding o f a monoclonal antibody to single-stranded DNA, The melanocytes; deriv ed from human foreskin of skin type II individuals were suspended and exposed to UVA, UVB, solar-simulated light or gamma-rays., Following p hysiological doses of UVA, UVB or solar-simulated light, a dose-relate d DNA unwinding comprising a considerable number of single-strand brea ks (ssb) was observed. No correlation was found between different seed ed cell densities or different culturing periods and the WA sensitivit y of the cells, After UVA irradiation, 0.07 ssb/10(10) Da/kJ/m(2) were detected and after UVB irradiation 1.9 ssb/10(10) Da/kJ/m(2) were see n. One minimal erythema dose of solar-simulated light induced 2.25 ssb /10(10) Da. Our results from melanocytes expressed? in ssb/Da DNA are comparable and have the same sensitivity toward UVA as well as toward UVB as nonpigmented skin cells, As low doses of UVA have already been shown to induce detectable numbers of ssb, this assay is of great inte rest for further investigations about the photoprotecting and/or photo sensitizing effects of melanins in human melanocytes derived from diff erent skin types.