Epidermal Synthesis of Prostaglandins and their Effect on Levels of Cyclic Adenosine 3',5'-Monophosphate

Extracts of guinea-pig and human skin epidermis were analyzed for prostaglandins PGE1, E2, and F2α, by radioimmunoassay, and found to contain a total of 62.0 (guinea pig) and 144.7 (human) ng/gm wet weight. The three prostaglandins occurred in approximately equal amounts.Guinea-pig epidermal homogenates converted labeled arachidonic acid to PGE2 and PGF2α, the rate of formation being 10 and 2.5 pmoles per mg protein in 0.5 hr. respectively. Conversion in the dermis occurred to a much smaller extent. Homogenates of uninvolved and involved epidermis from 10 subjects with psoriasis produced PGE2 from arachidonic acid at rates of 6.48 and 2.97 pmoles per mg protein, respectively, in 0.5 hr. These figures were significantly different statistically. The corresponding values for PGF2α were 1.10 and 0.51.The exposure of guineas-pig epidermal slices to isoproterenol (1–2 × 10-6 M) resulted in 2-fold to 5-fold increases in PGE (PGE1 + PGE2) levels in the tissue. Levels of PGF2α, were increased 2-fold at the higher concentration. Guinea-pig epidermal slices incubated with PGE2 (3–6 × 10-8 M) and theophylline (2 × 10-3 M) showed a 6-fold to 9-fold increase in cyclic AMP content, measured by radioimmunoassay. The effect of PGE2 was less pronounced. The lower ability of involved epidermal areas in psoriasis to produce PGE1 may account for the low levels of cyclic AMP in the lesions