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Effects of indomethacin on sunburn and suntan reactions in hairless
descendants of Mexican hairless dogs
T. Kimura1 and K. Doi2
1Research Center, Nihon Nosan Kogyo Co., Ltd., Takura,
Ibaraki, Japan and 2Department of Veterinary Pathology, Faculty of Agriculture,
The University of Tokyo, Bunkyo, Tokyo, Japan
Offprint requests to: Dr. T.
Kimura, Research Center, Nihon Nosan Kogyo Co., Ltd., Takura 5246, Ibaraki
300-26, Japan
Summary. The inhibitory effects
of topical indo-methacin (IM)-treatment on sunburn and suntan reactions
after ultraviolet (UV)-irradiation were investigated in the dorsal skin
of hairless descendants of Mexican hairless dogs. Skin color, plasma prostaglandin
E2 (PGE2) and histological features were examined. At 1 day after UV-irradiation,
the IM-untreated sites showed prominent erythema, while the IM-treated sites
exhibited few visible erythematous reactions. From 4 days after UV-irradiation,
both the IM-treated and -untreated sites began to develop skin pigmentation.
Assessment of skin color changes, using a colorimeter, reflected precisely
the color changes in visual sunburn and suntan reactions. Plasma PGE2 concentration
began to increase from 2 hours after UV-irradiation, reached the maximal
values at 24 hours and recovered at 96 hours after UV-irradiation. Histologically,
at 1 day after UV-irradiation, the IM-untreated sites showed remarkable
epidermal degeneration (thickening and sunburn cells) and moderate alteration
in the dermis. On the other hand, the IM-treated sites showed only minor
histological changes. At 4 days after UV-irradiation, deposition of melanin
granules was found in both the IM-treated and -untreated sites. At 7 days
after UV-irradiation, pig-mentation became more prominent in the stratum
basale. These results revealed that UV-induced erythematous reactions of
hairless dogs were closely related to the action of PGE2. Visually and histologically,
topical IM-treatment had apparent inhibitory effects on erythe-matous reactions,
while this agent showed no protective effects on epidermal pigmentation
after UV-irradiation. Histol Histopathol 13, 29-36 (1998)
Key words: Erythematous reactions,
Hairless dogs, Indomethacin, Prostaglandins, Ultraviolet
DOI: 10.14670/HH-13.29
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