Human ovarian expression of 17β-hydroxysteroid dehydrogenase types 1, 2, and 3

Three isozymes of 17β-hydroxysteroid dehydrogenase (17βHSD) have been cloned and characterized as distinct gene products (17βHSD1, 17βHSD2, and 17βHSD3). The presence and location of these isozymes in the human ovary have not been defined. In this study, we utilized Northern analysis and RT PCR to examine transcripts for the three isozymes of 17βHSD. RNA was isolated from ovarian cortex, stroma (pre- and postmenopausal), hilum, follicles, and corpora lutea obtained from adult women, as well as whole fetal ovaries. By Northern analysis, high levels of 17βHSD1 messenger RNA were found in follicles, corpora lutea, and cortex, whereas low levels were detected in the postmenopausal stroma and in fetal ovaries by RT-PCR. 17βHSD1 messenger RNA was not detected in hilar tissue by either Northern analysis or RT-PCR. Utilizing RT-PCR, transcripts for 17βHSD2 were not detectable in cortex, stroma, (pre- or postmenopausal), hilum, or follicles, but were present in RNA derived from the corpora lutea and fetal ovary. The androgenic isozyme 17βHSD3 was not detectable in any of the ovarian compartments examined by either Northern analysis or RT-PCR. These data provide additional insight into the mechanism of testosterone and estradiol synthesis within the ovary. Specifically, the high level of 17βHSD1 is clearly localized to follicles and corpora lutea indicating involvement in the synthesis of estradiol. Secondly, androgenic 17βHSD3 is not expressed in the human ovary. Thus testosterone production within the human ovary, occurring under physiological conditions, arises from either the 17βHSD1 or an uncharacterized isozyme.