PUVA suppresses the proliferative stimulus produced by stripping on hairless mice.

Hairless mice were fed with 8-methoxypsoralen by gastric tube and exposed to UVA light to produce threshold phototoxic reactions. 3H-thymidine autoradiography revealed no significant difference of the epidermal labelling index as compared to that of nonirradiated animals (4.8 vs 6.2). Single PUVA exposures performed 2,8,14 and 24 hr after tape stripping lead to suppression of a wave of synchronized DNA synthesis present in nonirradiated control animals. These data demonstrate different reactions of stripped and unstripped epidermis to PUVA exposures and offer indirect evidence for the suppression of DNA synthesis in hyperproliferative skin disorders by PUVA in vivo.