Ear swelling in response to UVB irradiation.

The skin response to UVB irradiation in mice was evaluated by means of ear swelling. ICR albino mice were irradiated with 500 mJ/cm2 UVB and the effect of various drugs on ear swelling was examined 24 h after irradiation. Intravenous injections of betamethasone (0.8 microgram/g body wt.) or indomethacin (24 micrograms/g) remarkably inhibited ear swelling, whereas intraperitoneal injections of diphenhydramine (20 micrograms/g), cimetidine (10 micrograms/g), or a combination of both these antihistamines did not. In contrast, the number of sunburn cells counted 24 h after UVB irradiation (200 mJ/cm2) in mouse ears was not affected by these drugs. The amount of prostaglandin D2 (PGD2) in mice ears at various intervals after irradiation with 500 mJ/cm2 UVB was determined by radioimmunoassay. Compared with the values before irradiation, the PGD2 levels were significantly higher 3 and 6 h after irradiation and gradually decreased and returned to the basal level by 12 h, although ear swelling continued after 12 h. These results suggest that prostaglandins are responsible at least in part for the development of ear swelling, but not for sunburn cell formation induced by UVB, and that ear swelling represents a simple and useful response model for the rapid in vivo screening of nonsteroidal or steroidal anti-inflammatory agents.