Topical spermine and putrescine stimulated DNA synthesis in the hairless mouse epidermis

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Abstract
Polyamines were applied topically to the skin of the hairless mouse. Putrescine stimulated the incorporation of thymidine [indicating increased DNA synthesis] after a 24-h application period. The effect of polyamines upon skin pretreated with a potent topical steroid [betamethasone valerate] was also examined; in this model thymidine incorporation was stimulated by both spermine and putrescine. Pretreatment was performed to reduce endogenous polyamine biosynthesis and increase the sensitivity of the epidermis to exogenous polyamines. Reduction of the activity of ornithine decarboxylase, the rate-limiting polyamine biosynthetic enzyme, by topical steroids was confirmed in the hairless mouse following induction of the enzyme by UVB. The results are consistent with those in vitro studies suggesting a role for polyamines in the control of DNA synthesis; the effect of corticosteroids upon proliferative skin disorders may be mediated through this mechanism.