The effect of steroid and dithranol therapy on cyclic nucleotides in psoriatic epidermis

Absolute values of both cAMP and cGMP leves were measured in the involved and uninvolved skin of psoriatic patients, and also the effect of topical therapy on these levels in the involved skin was studied. The mean cGMP level in the untreated psoriatic plaque was increased by 300% compared to the non-involved skin (which did not differ from normal skin), but no significant difference in cAMP levels was found. Epidermal stripping of uninvolved skin, which stimulates cell proliferation, did not change the cGMP level. Treatment of the psoriasis with dithranol caused the cGMP levels to return to normal, but a potent topical glucocorticoid, in contrast, produced no such decrease. This may imply that the two drugs act at different levels in suppressing cell replication, and dithranol may be a useful tool for the further investigation of cyclic nucleotide metabolism.