EVIDENCE OF HETEROGENEITY AND QUANTITATIVE DIFFERENCES OF THE TYPE-1 5-ALPHA-REDUCTASE EXPRESSION IN CULTURED HUMAN SKIN CELLS - EVIDENCE OF ITS PRESENCE IN MELANOCYTES

Steroid 5 alpha-reductase is of crucial importance in androgen physiol ogy because it catalyzes the conversion of testosterone into the more potent 5 alpha-dihydrotestosterone in androgen-regulated target tissue s, The enzyme occurs in two isoforms, whereby type 1 isozyme exists ma inly in the skin and type 2 in the prostate, By using human cell cultu res, we examined cutaneous expression and subcellular localization of type 1 5 alpha-reductase in vitro. In immunocytochemistry, type 1 5 al pha-reductase was detected in the cytoplasm of cultured human sebocyte s, keratinocytes, fibroblasts, dermal microvascular endothelial cells, hair dermal papilla cells, and melanocytes. In western blot studies, two closely lying bands of 21-27 kDa were detected, possibly indicatin g heterogeneity of the type 1 5 alpha-reductase in all the cell types tested, with the exception of beard dermal papilla cells, Northern blo t studies revealed most abundant type 1 mRNA in neonatal foreskin kera tinocytes, followed by adult facial sebocytes, Occipital hair dermal p apilla cells presented higher levels of type 1 5 alpha-reductase mRNA than those of beard, These findings were confirmed by semiquantitative reverse transcriptase polymerase chain reaction coupled with high per formance liquid chromatography analysis, Taken together, it seems like ly that in cultured human skin cells there exist (i) heterogeneity of type 1 5 alpha-reductase protein and (ii) quantitative differences in its transcriptional and translational expression levels.