WAVELENGTH DEPENDENCE FOR ORNITHINE DECARBOXYLASE INDUCTION IN VIVO†

Abstract

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.