INDUCTION OF SISTER-CHROMATID EXCHANGES IN FIBROBLASTS FROM NORMAL DONORS AND FROM PATIENTS WITH XERODERMA-PIGMENTOSUM AFTER COMBINED TREATMENT WITH ULTRAVIOLET-RADIATION AND MODULATED LOW-FREQUENCY ELECTRIC CURRENTS

Dermal fibroblasts derived from normal donors as well as from patients with xeroderma pigmentosum (XP) were exposed in vitro to ultraviolet radiation of 254 nm wavelength and to weak electric 4,000 Hz currents modulated in amplitude with 50 Hz, Treatment with this so-called inter ferential current (IFC) increased the rate of sister chromatid exchang es (SCE) in all fibroblast types up to roughly 50% above the spontaneo us level. When IFC was applied in combination with UV-radiation, it lo wered UV-induced increase of the SCE-rate. A reduction of UV-induced S CEs was seen when XP-cells were exposed to IFC prior to UV-treatment, compared to the reverse order of treatment. The order of exposure has only been analysed in 5 XP patients, not in normal donors. The relatio nships between different combinations of exposure parameters (IFC-ampe rage, UV-dose, cell pathology, order of treatment) were examined by an alysis of variance (ANOVA).