PHOTOSENSITIZING EFFECTS OF 8-METHOXYPSORALEN ON THE SKIN OF HAIRLESS MICE—I. FORMATION OF INTERSTRAND CROSS-LINKS IN EPIDERMAL DNA

Abstract— The photomediated induction of interstrand cross-links by 8-methoxypsoralen has been measured in the epidermal DNA of hairless mice. Equivalent efficiencies for cross-link induction were determined for HRS/J/Anl and SKH: hairless-1 mice. A wavelength dependence on the relative efficiency of cross-link induction was observed; a broad spectrum light source, 300–400 nm, was approximately 5 times more effective in cross-link formation than a 365 nm light source. Repeated exposure to 8-methoxypsoralen followed by ultraviolet light, 5 times a week for 6 weeks, altered epidermal thickness and resulted in a decreased efficiency for DNA cross-link formation.