Effect of topical indomethacin on UVR-induced redness and prostaglandin E levels in sunburned guinea pig skin.

Prostaglandin E (PGE) levels in the skin have been shown to be elevated during the 24 hr. period following exposure of guinea pig skin to ultraviolet radiation from 280-320 nm in the so-called UVB or "sunburn spectrum". The development of increased PGE levels paralleled the development of the delayed phase of erythema. When applied immediately after UVB exposure, one topical application of 2.5% Indomethacin (IM) simultaneously decreased the redness and PGE levels in the skin to near normal within one hr. of treatment. The IM effect persisted for approximately 24 hrs. By 48 hrs. the PGE level in the sunburned skin was near normal whether or not the skin had been treated with IM. The redness which was evident at 48 hrs. did not respond to additional topical IM treatment. This suggests that a substance(s) other than PGE may be involved in this latter portion of UVB-induced erythema. A major role for PGE as an early mediator or potentiator of UVB-induced erythema has been deomonstrated. Any involvement of PGE with UVB-induced cell death or alterations in DNA synthesis seems unlikely.