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1 July 2001 3α-Hydroxysteroid Dehydrogenase Messenger RNA Transcription in the Immature Rat Ovary in Response to an Ovulatory Dose of Gonadotropin
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The ovulatory process in mammals involves a substantial increase in the metabolism of steroids and eicosanoids in response to a surge in LH or to an injection of hCG into experimental animals. This study provides evidence that the ovulatory stimulus causes induction of the gene for 3α-hydroxysteroid dehydrogenase (3α-HSD), an enzyme that belongs to several oxidoreductase superfamilies that affect steroid and eicosanoid metabolism. Immature Wistar rats were primed with 10 IU eCG s.c., and 48 h later the 12-h ovulatory process was initiated by 10 IU hCG s.c. Ovarian RNA was extracted at 0, 2, 4, 8, 12, and 24 h after injecting the animals with hCG. The RNA extracts were used for reverse transcription-polymerase chain reaction (PCR) differential display to detect gene expression in the stimulated ovarian tissue. One of the PCR primer sets differentially amplified a cDNA fragment that is 52.3% homologous with a 3α-HSD gene in rat liver. Northern analyses revealed that maximum transcription was at 8 h after the animals had been treated with hCG. The Northerns also indicated that the 3α-HSD cDNA probe cross-hybridized with as many as six different bands of mRNA on the blots. In situ hybridization localized 3α-HSD mRNA in the granulosa and thecal layers of mature follicles and in newly formed corpora lutea at 24 h after the ovulatory stimulus. In conclusion, gene(s) for 3α-HSD are transcribed in ovarian follicles in response to an ovulatory dose of gonadotropin. A possible function of the oxidoreductase enzyme that is translated from the 3α-HSD mRNA may be to reduce the toxic aldehyde and ketone components of the steroids and eicosanoids that accumulate in the mammalian ovary at the time of ovulation.

Lawrence L. Espey, Shinya Yoshioka, Takeshi Ujioka, Shingo Fujii, and JoAnne S. Richards "3α-Hydroxysteroid Dehydrogenase Messenger RNA Transcription in the Immature Rat Ovary in Response to an Ovulatory Dose of Gonadotropin," Biology of Reproduction 65(1), 72-78, (1 July 2001).
Received: 19 September 2000; Accepted: 1 February 2001; Published: 1 July 2001

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