Endocrinology, Vol 131, 2755-2762, Copyright © 1992 by Endocrine Society

ARTICLES

Oxytocin/neurophysin-I messenger ribonucleic acid in bovine granulosa cells increases after the luteinizing hormone (LH) surge and is stimulated by LH in vitro

AK Voss and JE Fortune
Department of Physiology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853.

Bovine granulosa cells express the oxytocin/neurophysin-I (OT/NP-I) gene and secrete OT in vitro. We have shown previously that bovine granulosa cells isolated from the preovulatory follicle after the LH surge secrete 20 times more OT over 5 days in culture than granulosa cells obtained before the surge. LH or FSH stimulates OT secretion in vitro by granulosa cells isolated before the LH surge. We also observed that granulosa cells of preovulatory follicles isolated before the LH surge respond to OT with an increase in progesterone secretion, suggesting that OT may be involved in regulating the follicular/luteal phase shift, or ovulation, in an autocrine fashion. The objective of this study was to determine whether the increase in OT secretion from granulosa cells after the LH surge is regulated at the level of mRNA accumulation, peptide synthesis, and/or peptide secretion. Bovine preovulatory follicles were obtained during the early follicular phase (approximately 36 h before the LH surge), during the midfollicular phase (approximately 12 h before the LH surge), or during the late follicular phase (after the LH surge). Total RNA isolated from granulosa cells and theca interna at the time of cell isolation or after culture with or without LH was subjected to Northern analysis for OT/NP-I mRNA and quantified by densitometry. OT/NP-I mRNA was not detectable or was barely detectable in granulosa cells collected during the early or midfollicular phase (n = 6 and n = 4 follicles, respectively), but a strong hybridization signal was obtained from RNA isolated after the LH surge (n = 5 follicles; P < 0.01). In contrast, OT/NP-I mRNA was not detectable in theca interna before or after the LH surge. Although OT/NP-I mRNA was not detectable in granulosa cells isolated 24 h after prostaglandin F2 alpha injection, after 24 h in culture, a weak OT/NP-I mRNA hybridization signal was observed in RNA from granulosa cells in LH-containing cultures. After 72 h in culture, granulosa cells cultured in control, as well as in LH-containing medium, exhibited a strong signal for OT/NP-I mRNA, but granulosa cells treated with LH exhibited a stronger OT/NP-I hybridization signal than control cultures (P < 0.01). Theca interna did not yield any OT/NP-I hybridization signal initially, and none was induced in culture.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				Q. Li, F. Jimenez-Krassel, A. Bettegowda, J. J Ireland, and G. W Smith Evidence that the preovulatory rise in intrafollicular progesterone may not be required for ovulation in cattle J. Endocrinol., March 1, 2007; 192(3): 473 - 483. [Abstract] [Full Text] [PDF]

				G. M. Rivera and J. E. Fortune Selection of the Dominant Follicle and Insulin-Like Growth Factor (IGF)-Binding Proteins: Evidence that Pregnancy-Associated Plasma Protein A Contributes to Proteolysis of IGF-Binding Protein 5 in Bovine Follicular Fluid Endocrinology, February 1, 2003; 144(2): 437 - 446. [Abstract] [Full Text] [PDF]

				M. Jo, C.M. Komar, and J.E. Fortune Gonadotropin Surge Induces Two Separate Increases in Messenger RNA for Progesterone Receptor in Bovine Preovulatory Follicles Biol Reprod, December 1, 2002; 67(6): 1981 - 1988. [Abstract] [Full Text] [PDF]

				G.M. Rivera, Y.A. Chandrasekher, A.C.O. Evans, L.C. Giudice, and J.E. Fortune A Potential Role for Insulin-Like Growth Factor Binding Protein-4 Proteolysis in the Establishment of Ovarian Follicular Dominance in Cattle Biol Reprod, July 1, 2001; 65(1): 102 - 111. [Abstract] [Full Text] [PDF]

				T. J. Acosta, B. Berisha, T. Ozawa, K. Sato, D. Schams, and A. Miyamoto Evidence for a Local Endothelin-Angiotensin-Atrial Natriuretic Peptide Systemin Bovine Mature Follicles In Vitro: Effects on Steroid Hormones and Prostaglandin Secretion Biol Reprod, December 1, 1999; 61(6): 1419 - 1425. [Abstract] [Full Text]