Wavelength dependence for ornithine decarboxylase induction in vivo

Abstract— The wavelength dependence for ornithine decarboxylase induction was investigated in vivo in the epidermis of albino hairless mice. A 4 cm² area of dorsal skin was exposed to narrow wavebands (HPBW 6.6 nm) from a monochromator optically coupled to a 5 kW Xe arc source. Dose-response studies were caried out at 260, 275, 290, 300 and 315 nm. The animals were sacrificed 24 h after irradiation and the epidermis separated and assayed for ODC activity. A dose-related induction of ODC was observed at 260, 275, 290 and 300 nm. No stimulation was observed following exposure to 315 nm (maximal dose 6400 J/m²). ODC induction appeared to be linearly related to log UV dose within the dose range of 200 to 1600 J/m². The dose required to induce an approximately 50-fold increase in activity (1.5 nmol CO₂/h/mg protein) was determined from the dose-response regression lines and used to construct an action spectrum. Peak effectiveness occurred at 290 nm, with a rapid loss after 300 nm. After correction for epidermal transmission, peak effectiveness was shown to occur around 260 nm.