Molecular and Cellular Endocrinology 15 January 2007 [antikvár]

ELSEVIER Molecular and Cellular Endocrinology 263 (2007) i MCE Molecular tad Cellubr Enaocripology www.elsevjer.com/locate/mce Regulation, action and transport of prostaglandins during the periovulatory period in cattle^ P.J. Bridges K J.E. Fortune* Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14S53, United Slates Received 13 January 2006; received in revised form 24 July 2006; accepted 10 August 2006 Abstract Follicular production of prostaglandins (PGs) is essential for mammalian ovulation, but the factors that mediate production and the cell-specific action(s) of PGE and PGFja during the ovulatory cascade remain largely unknown. The aims of these experiments were; (1) to investigate the potential role of oxytocin (OT) in ovulatory PG production, (2) to determine cellular and temporal patterns of expression of mRNA for specific PG receptors during the periovulatory interval, (3) to determine cell-specific effects of PGE2 on progesterone secretion, and (4) to investigate the potential for an active transport mechanism that may regulate the effect of PGs during the ovulatory cascade, using cattle as the animal model. Heifers were treated sequentially with POFj^ and GnRH to induce luteal regression, a follicular phase and the LH/FSH surge (ovulation occurs ~30h after GnRH). In experiment 1, OT increased the secretion of PGE and PGF2„ by granulosa cells collected from preovulatory follicles (before die LH/FSH surge) and OT production by pieces of follicle wall from periovulatory follicles (after the LH/FSH surge) was regulated by progesterone acting through the progesterone receptor. In experiment 2, levels of mRNA for the PGF2a receptor and three PGE receptor subtypes were determined by semi-quantitative RT-PCR in flieca interna and granulosa cells from pre- and periovulatory follicles collected at 0, 6, 12, 18 and 24 h post-GnRH. Time- and cell-specific patterns of change in mRNA for PG receptors were observed, suggesting multiple effects of both PGE and PGFic in both theca intema and granulosa cells throughout the ovulatory cascade. Cell-specificity of PG action was confirmed in experiment 3; PGE2 increased the secrerion of progesterone by theca intema but not granulosa cells collected from late periovulatory follicles. The results of experiment 4 revealed die expression of mRNA for the bovine PG transporter in Uieca intema and granulosa cells and its regulation during the periovulatory period, thus reveaUng the presence of a potential transport mechanism that could regulate cellular distribution of PGs throughout the ovulatory cascade. Taken together, these results provide new insight into mechanisms that regulate the production, distribution and site of action of PGE and PGF2„ during the ovulatory cascade. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Ovary; Ovarian follicle; Prostaglandin receptors; Oxytocin; Ovulation 1. Introduction In cattle (Algireetal., 1992; DeSilva and Reeves, 1985), as in other mammals (Barbosa et al., 1979; Killick and Elstein, 1987; Mikuni et al., 1998; Murdoch et al., 1986; Priddy et al., 1990), gonadotropin-induced follicular production of prostaglandins (PGs) is required for ovulation. We previously reported that gonadotropin-induced production of both PGE and PGF2a by bovine granulosa cells is regulated by progestin acting through * This research was supported by the National Institutes of Health (HD4I592 to JEF) and a Lalor Foundation Fellowship (PJB). • Corresponding author. Tel.: +1 607 253 3466; fax: +1 607 253 3476. E-mail address: JFl 1 Scomell.edu (J.E. Fortune). ' Present address: Department of Clinical Sciences, University of Kentucky, Lexington, KY 40536, LInited States. the progesterone receptor (PR; Bridges et al., 2006). Concentrations of progesterone in the follicular fluid of bovine periovulatory foUicIes and expression of mRNA for the PR in folUcular cells increase transiently, peaking shortly after the preovulatory LH/FSH surge and then increasing again late in the periovulatory period (Jo et al., 2002). Progesterone also stimulates production of oxytocin (OT) by bovine granulosa cells (Lioutas et al., 1997; Voss and Formne, 1991a). Expression of mRNA for OT/neiffophysin-I in granulosa cells and follicular fluid concentrations of OT begin to increase about midway through the bovine periovulatory period (Fortune et al., 2000; Jo and Fortune, 2003), whereas, expression of mRNA for prostaglandin G/H synthase-2 (PGHS-2, also known as COX-2) and concentrations of PGE and PGF20; in the follicular fluid remain low until late in the periovulatory period, increasing dramatically in the hours preceding ovulation (Bridges et al., 2006; 0303-7207/$ - see front matter © 2006 Elsevier Ireland Ltd. All rights reserved, doi; 10.1016/j.mce.2006.08.002