5alpha-reductase 1 and 2 expression and activity in human ovarian follicles, stroma and corpus luteum as compared to...

5alpha-Reductase is the steroidogenic enzyme which reduces testosterone to 5alpha-dihydrotestosterone. In the human two different enzymes have been described, 5alpha-reductase 1 and 2. The present investigations were undertaken to determine whether 5alpha-reductase 1 and 2 were expressed in the human ovary, and to determine the relative activity of the two enzymes in various ovarian tissues. The ovary apparently expressed mRNA for only 5alpha-reductase 1, whereas the foreskin expressed both 5alpha-reductase 1 and 2. We compared the 5alpha-reductase activity at both pH 5.5 (optimum for 5alpha-reductase 2 activity) and 8.0 (optimum for 5alpha-reductase 1 activity). 5alpha-reductase activity of foreskin at pH 5.5 was 3900 times higher than small follicles, 1500 times higher than ovarian stroma, and 240 times higher than corpora lutea (all P < 0.01). 5alpha-reductase activity of corpora lutea at pH 5.5 was 17-fold higher than that of follicles (P < 0.01) and 6.5-fold higher than that of ovarian stroma (P < 0.05). 5alpha-Reductase activity of foreskin at pH 8.0 was 93 times higher than small follicles, 51 times higher than corpora lutea, and 170 times higher than ovarian stroma (all P < 0.01). The ratio of 5alpha-reductase activity at pH 5.5 to that at pH 8.0 was higher in foreskin than in corpus luteum (P < 0.05), ovarian stroma (P < 0.01), or ovarian follicles (P < 0.01). The ratio was lower in ovarian follicles than in stroma or corpus luteum (both P < 0.05).