The Effect of Systemically and Topically Applied Drugs on Ultraviolet‐induced Erythema in the Rat

Abstract

Exposure of the skin of rats to u.v. light (>295 nm) for 30 s or longer elicited a delayed erythema response, the rate of onset increasing with the period of irradiation. The erythema was still present at 24 h and was replaced by scab formation in 48 hours. Both topically applied steroidal and non‐steroidal anti‐inflammatory drugs reduced the erythema formation when administered immediately after u.v. exposure. Propyl gallate, an antioxidant with sun screening properties in man, also possessed topical anti‐erythemic activity. Both steroidal and non‐steroidal anti‐inflammatory drugs, systemically administered 1 h before u.v. exposure, reduced the erythema. However, the steroidal compounds were less effective than the nonsteroids and reduced the intensity of erythema by less than 50%. Antagonists of 5‐hydroxytryptamine (5‐HT) reduced the erythema but several other drugs with different pharmacological activities were ineffective. Neither topical nor systemic treatments of any of the drugs examined suppressed the scab formation at 48 hours. These results and those using other selective blocking agents indicate that in the mediation of the erythema reaction prostaglandins may play a major role and 5‐HT perhaps a minor one but that H1 histamine receptors and α‐ and β‐adrenoceptors have no significant role.

Production of ultraviolet-light-induced skin erythema in the hairless rat: a comparison with the haired rat in screening for anti-inflammatory drugs

“…Results and discussion Law & Lewis, 1977). In both hairless and haired animals the intensity of erythema increased with increasing exposure time up to 3 h after the irradiation, with the mean erythema scores in fairly close agreement.…”

“…The guinea-pig (Swingle, 1974) and normal albino haired rat (Law & Lewis, 1977) have been described as suitable models for the production of skin erythema by ultraviolet (UV) light for the purpose of the assessment of new anti-inflammatory drugs. The albino hairless rat, designated 'atrichis', which appeared as an autosomal recessive mutation in a Wi star strain maintained by the Centre de Selection et d'Elevage d'Animaux de Laboratoire, Orleans-la-Source, France (CSEAL) could be a promising alternative.…”

“…2a shows the response of hairless rats to the 2 drugs, and Fig. 2b shows the comparative data from haired rats (from Law & Lewis, 1977). Up to 4 h it is clear that the suppression of onset of erythema corresponds closely between drugs and between animals.…”

“…In a 1st experiment various exposure times were examined as previously described for haired rats (Law & Lewis, 1977). The intensity of erythema of each irradiated area was similarly visually assessed by a trained observer at several intervals after UV exposure.…”

Two simple methods for the evaluation of topically active anti-inflammatory steroidal ointments

“…TONELLI and his associates [4] devised the croton oil ear edema method for the determination of topical anti-inflammatory activity in animal models. The cantharidin ear edema method [5], ultra violet erythema method [6] and sulfuric-croton oil ear edema method [7] were also reported. In these methods, however, test compounds dissolved in organic solvents instead of formulated ointment were usually applied to the inflammatory sites.…”