title: Kinetics of photobleaching of protoporphyrin IX in the skin of nude mice exposed to different fluence rates of red light.
abstract: The purpose of the present study was to determine the kinetics and the fluence rate dependency of the photobleaching of protoporphyrin IX (PpIX) in normal skin of Balb/c nude mice after systemic and topical application of 5-aminolevulinic acid (ALA). ALA was administered systemically (200 mg/kg body weight, i.p.) and topically (20% w/w ALA cream) to the mice. Fluences of up to 40 J/cm2 were delivered by a dye laser (636 nm) at fluence rates of 37.5, 75, 150, 300 and 500 mW/cm2. The photo-bleaching rate was constant within this range of fluence rates. This result suggests that there is no oxygen effect for PpIX photobleaching in this region for the skin of Balb/c nude mice. During light exposure the fluorescence decay followed neither first- nor second-order kinetics. The decay rate was slightly faster after systemic application than after topical application of ALA, but did not depend on the time (1-8 h) between application and analysis.
authors.affiliation: Department of Biophysics, Institute for Cancer Research, Oslo, Norway. roar.sorensen@labmed.uio.no
authors.forename: R
authors.initials: R
authors.lastname: Sørensen
authors.forename: V
authors.initials: V
authors.lastname: Iani
authors.forename: J
authors.initials: J
authors.lastname: Moan
mesh_terms: D000287:Administration, Topical; D000622:Aminolevulinic Acid / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D005260:Female; D007700:Kinetics; D008027:Light; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000378:metabolism* / Q000528:radiation effects; D011524:Protoporphyrins / Q000378:metabolism* / Q000528:radiation effects; D012867:Skin / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D013050:Spectrometry, Fluorescence
chemical_list: D017319:Photosensitizing Agents; D011524:Protoporphyrins; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX