title: Early changes in dermal collagen of mice exposed to chronic UVB irradiation and the effects of a UVB sunscreen.
abstract: Our previous studies have shown that hairless albino mice receiving chronic UVB irradiation show an increase in type III collagen, in the irradiated skin, after 12-36 weeks treatment. In this study we wished to find the earliest time at which such collagen changes were detectable and also to ascertain whether a topically applied UV-B sunscreen could prevent such changes. Groups of 10 hairless albino mice were irradiated, dorsally, with a daily dose of 62 mJcm-2 UVB for 3, 6, 9, and 12 weeks. Three parallel groups were used. They received a) no topical treatment, b) sunscreen vehicle alone, and c) sunscreen (containing 2-ethylhexyl 4'-methoxy-cinnamate) applied dorsally at 2 microliter cm-2. Dorsal and ventral (non-irradiated) skin samples were taken and the types I and III collagen quantified densitometrically after cyanogen bromide digestion and polyacrylamide gel electrophoresis. The ratio of dorsal/ventral type III collagen (D/V III) was determined for each mouse. The topical treatments caused no change in D/V III in the non-irradiated animals. In the non-topically treated group the irradiated animals showed a considerable increase in D/V III, compared with controls, at 12 weeks (P less than 0.001). The group treated with sunscreen vehicle alone also showed a significant increase in D/V III at week 12 (P less than 0.01). Both these groups showed a slight elevation in D/V III at week 6. The group treated with sunscreen showed no significant difference in D/V III between irradiated and control animals at any time.
authors.affiliation: Institute of Dermatology, United Medical School, Guy's Hospital, London, United Kingdom.
authors.forename: S R
authors.initials: SR
authors.lastname: Plastow
authors.forename: J A
authors.initials: JA
authors.lastname: Harrison
authors.forename: A R
authors.initials: AR
authors.lastname: Young
mesh_terms: D000818:Animals; D003094:Collagen / Q000528:radiation effects*; D005260:Female; D051379:Mice; D008812:Mice, Hairless; D012867:Skin / Q000528:radiation effects; D013473:Sunscreening Agents / Q000494:pharmacology*; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D013473:Sunscreening Agents; D003094:Collagen