THE EFFECT OF TOPICAL STEROID ON THE ACTIONS OF VASOCONSTRICTOR AND VASODILATOR PEPTIDES IN HUMAN SKIN

The effect of topical application of clobetasol propionate ointment (0 .05% w/v) on the vascular changes induced by intradermal injections of histamine, calcitonin gene-related peptide, substance P, endothelin-1 and compound 48/80 was studied. Clobetasol propionate ointment was ap plied topically under occlusion to the forearm skin of healthy volunte ers and vehicle base was applied to the contralateral forearm. The int radermal injections were made 4 h or, in a separate study, 72 h after topical steroid application. Responses were measured by planimetry and laser Doppler flowmetry. Four hours application of steroid did not si gnificantly alter the responses to any of the vasoactive substances. A fter 72 hours application, clobetasol propionate significantly increas ed the size of the endothelin-1-induced area of vasoconstriction (p < 0.02) and significantly reduced the size of the flares induced by endo thelin-1 (p < 0.02), substance P (p < 0.009) and compound 48/80 (p < 0 .05). We conclude that the most likely explanation of our data is an i nhibition by the steroid of cutaneous mast cell function.