The effects of topical and systemic glucocorticosteroids on DNA synthesis in different tissues of the hairless mouse

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Abstract
Two topical corticosteroids, clobetasol propionate and clobetasone butyrate, were studied in hairless mice for their effects on DNA synthesis in the epidermis, thymus and spleen. Following topical application, both clobetasol propionate and clobetasone butyrate showed significant activity at the site of application throughout the range of concentrations tested (20 .mu.l; 0.0001-0.1%; 20 ng to 20 .mu.g). While 20 ng clobetasol propionate also elicited significant effects in the distal (untreated) epidermis and the thymus, > 2 .mu.g of clobetasone butyrate were required to produce similar effects in these tissues. Following i.v. administration of equivalent doses (0.01 and 0.001%; 200 .mu.l dose) of the same 2 steroids, only clobetasol propionate unexpectedly showed significant activity in the epidermis and thymus. Clobetasone butyrate showed slight, non-significant effects in the epidermis at the highest concentration (200 .mu.l; 0.01%), but not in the thymus or spleen. Effects following i.v. injection were unexpectedly lower than those following topical application. Effects on DNA synthesis in the epidermis at a site distal to application site are indicative of systemic activity from topically applied corticosteroids. The thymus is especially sensitive to corticosteroids eliciting systemic effects and an equivalent dose of a topical corticosteroid administered i.v. produces less inhibition of thymic and epidermal DNA synthesis than the same dose applied topically.