title: Testosterone and UVL-B stimulation of epidermal melanocytes in rat scrotal skin.
abstract: The effects of UVL-B and/or testosterone replacemnt therapy are compared in normal and castrated rats in order to determine whether testosterone is required for UVL-B (290-315 nm) stimulation of melanogenesis in the testosterone-dependent epidermal melanocyte system of the scrotal skin of black Long Evans rats. Testosterone is not a prerequisite for UVL-B stimulation of melanocytes as in both castrates and normal animals the melanocytes respond to UVL-B by increases in size, length and number of dendrites (dendriticness), and tyrosinase activity (intensity of Dopa reaction). Addition of testosterone to castrates does enhance the effects of UVL-B. However, UVL-B with or without testosterone cannot maintain normal melanogenesis in rats irradiated immediately after castration nor can it restore normal melanogenesis following long term castration. Bth the amount of UVL nergy/exposure and the number of exposures are important variables in stimulation of the epidermal melanocytes. Administration of a dose of UVL-B to castrates in a single exposure is ineffective, while the same overall dose spread over several exposures increases the size and dendriticness of melanocytes. Testosterone and UVL-B act synergistically in affecting melanogenesis although neither singly nor in combination are they able to fully restore normal melanogenesis.
mesh_terms: D000818:Animals; D002369:Castration; D002452:Cell Count; D008297:Male; D008544:Melanocytes / Q000166:cytology* / Q000187:drug effects / Q000528:radiation effects; D051381:Rats; D012611:Scrotum / Q000166:cytology*; D012867:Skin / Q000166:cytology; D013739:Testosterone / Q000494:pharmacology*; D014466:Ultraviolet Rays
chemical_list: D013739:Testosterone