Oxytocin secretion by bovine granulosa cells increases dramatically after the LH/FSH surge. We have shown that oxytocin stimulates progesterone secretion and inhibits FSH-stimulated estradiol secretion in vitro by granulosa cells from bovine preovulatory follicles obtained before the LH/FSH surge. To determine if oxytocin regulates LH-stimulated steroid production by bovine theca interna cells, theca cells were isolated from preovulatory follicles obtained before the LH surge and were cultured for 4 days in the presence or absence of LH (2 or 4 ng/ml), without or with graded doses of oxytocin (125-1000 ng/ml). LH increased accumulation of androstenedione and progesterone. Oxytocin inhibited LH-stimulated androstenedione production, but had no effect on LH-stimulated progesterone production by cultured theca interna. The next objective was to determine if oxytocin regulates LH-stimulated steroidogenesis by modulating the levels of mRNA for steroidogenic enzymes and/or Steroidogenic Acute Regulatory protein (StAR). Low doses of LH alone increased the levels of mRNA for P450 17α-hydroxylase (17α-OH), 3β-hydroxysteroid dehydrogenase (3β-HSD) and cytochrome P450 side-chain cleavage, but not for StAR. In contrast, the effects of oxytocin on LH-stimulated androstenedione production were not associated with changes in the levels of mRNA for steroidogenic enzymes or StAR. These results suggest that oxytocin may play a paracrine role in regulating the follicular/luteal phase shift in steroidogenesis by decreasing androstenedione secretion by theca cells of the ovulatory follicle and that this effect is not mediated by changes in the levels of mRNA for steroidogenic enzymes and StAR.
|Number of pages||9|
|Journal||Molecular and Cellular Endocrinology|
|State||Published - Feb 25 2002|
Bibliographical noteFunding Information:
This work was supported by a USDA grant (#96-35203-3450). The authors thank S.E. Vincent for technical assistance, D. Bianchi for care of the animals and Dr S.M. Quirk for reading the manuscript. We wish to thank the National Hormone and Pituitary Program (supported by NIDDKD, the Center for Population Research of the NICHD, and the Agricultural Research Service of the USDA) for providing LH, Drs D.T. Armstrong and W. Hansel for the antisera to androstenedione and progesterone, and Dr R. Ivell for the StAR cDNA.
- Ovary (bovine)
- Theca cells
ASJC Scopus subject areas
- Molecular Biology