The effects of indomethacin on arachidonic acid and prostaglandins e2 and f2alpha levels in human skin 24 h after u.v.B and u.v.C irradiation.

1 Clinically normal human abdominal skin was irradiated with either three times its minimal erythema dose (MED) of ultraviolet B (u.v.B) or six MEDs of ultraviolet C (u.v.C) radiation. In both instances erythema was maximal at 24 h. 2 Exudate was recovered by a suction bulla technique from normal and irradiated skin at 24 h after irradiation. 3 Arachidonic acid, prostaglandins E2 and FSalpha, as measured by GC--MS, were significantly elevated at 24 h. Radioimmunoassay also showed increased PGF2alpha-like concentrations. 4 Oral indomethacin only partially reduced the erythema resulting from both types of radiation but totally suppressed the elevation of PGE 2 and F2alpha concentrations. 5 Topical indomethacin also suppressed u.v.B-induced increases in prostaglandins E2 and F2alpha. Unexpectedly, the vehicle alone produced a similar suppressive effect on prostaglandins although erythema appeared unaltered. 6 Most of the arachidonic acid metabolized by indomethacin-sensitive pathways is not converted to prostaglandins E2 and F2alpha in human skin.