PARENT SESSION
OVARY - A

Monday, August 2, 2004
10:30 AM–12:30 PM
Buchanan Courtyard

(191) THE EXPRESSION OF BASIC FIBROBLAST GROWTH FACTOR (FGF2) AND ITS RECEPTORS IN BOVINE FOLLICLE BEFORE AND AFTER THE LH SURGE.

Schams, Dieter¹, Berisha, Bajram¹, Kraetzl, Wolf Dieter¹, Amselgruber, Werner², ¹ Physiology, Freising, Germany² Institute of Anatomy and Physiology, Stuttgart, Germany

ABSTRACT- The aim of this study was to investigate the possible participation of basic fibroblast growth factor (FGF2) and its receptors FGFR1IIIc and FGFR2IIIc in follicle before and after LH surge. Cows were treated for multiple ovulations by FSH treatment and luteolysis was induced on the 3rd day by PGF2 analog (cloprostenol, 500 g i.m.) injection. 40h later the LH surge was induced by GnRH application. The ovaries were collected by transvaginal ovariectomy (n=4-5 cows/group). The follicles were classified in 5 groups: (I) before LH-surge; (II) 3-5h after GnRH application (during LH-surge); (III) 10h after GnRH; (IV) 20h after GnRH; (V) 25h after GnRH (peri-ovulation) and (VI) corpus luteum (CL, d 1-3). For better characterization of follicle classes, estradiol-17 (E), progesterone (P), prostaglandin (PG) F2 and PGE2 were determined by EIA in follicular fluid (FF). The mRNA expression of examined factors were analyzed by RT-PCR, and FGF2 protein localization by immunohistochemistry. There was a significant up-regulation of FGF2 mRNA expression in follicles only during LH peak and 10h after LH peak with significant down-regulation afterwards. The mRNA of FGFR1IIIc mRNA was significantly higher in all follicle classes during and after LH peak. The mRNA expression of FGFR2IIIc decreased continuously and significantly during and after LH surge with significant down-regulation around ovulation phase (V). FGF2 protein in (I) was localized in theca tissue (endothelial and muscle cells of blood vessels) but not in granulosa cells (GC). But staining pattern for FGF2 changed dramatically after the LH surge. FGF2 protein is now localized in the nucleus (nucleolus) of many GC, and most of capillary endothelial cells are no longer positive. We assume that the nuclear localization of FGF2 indicates an important step for transition of GC to luteal cells by stimulation of transcription of ribosomal genes which is preceded by an increase of the protein nucleolin (as shown in vitro). The direct action of FGF2 on the level of ribosomal gene transcription could correspond to an additional growth-signaling pathway, mediated by this growth factor.

KEY WORDS: FGF2 expression, Follicle, LH surge, bovine