Abstract: 48

EXPRESSION OF mRNA FOR THE INSULIN-LIKE GROWTH FACTOR (IGF) SYSTEM DURING THE INITIATION OF OVARIAN FOLLICULAR GROWTH.

J. Liu¹ , P. E. Davis¹ , M. C. Lucy^{1 *}
University of Missouri, Columbia ¹

The neonatal pig ovary contains a large number of follicles in the earliest phases of growth. The objective was to characterize mRNA expression for IGF system genes within primordial, primary and secondary follicles by using the neonatal pig ovary as a model system. Ovaries from four neonatal pigs (26±2 d of age) were collected after slaughter. Messenger RNA for growth hormone receptor (GHR), IGF-I, type I IGF receptor (IGF-IR), IGF-II, type II IGF receptor (IGF-IIR), and IGF binding protein (BP)-2 were quantified by using in situ hybridization with antisense and sense (background) RNA probes. The neonatal pig ovary did not express IGF-I mRNA above background (P>.10). The mRNA for GHR (signal within oocytes), IGF-IR (signal within oocytes, pregranulosa, and granulosa cells) and IGF-IIR (signal within oocytes) were present in the neonatal pig ovary but the mRNA signal was similar within primordial, primary, and secondary follicles (P>.10). The IGF-II and IGFBP-2 mRNA were detected in pregranulosa and granulosa cells and had opposite patterns of expression. The IGF-II mRNA signal decreased (57.8, 12.1, and 2.7 units; SEM=4.1; P<.001); whereas, the IGFBP-2 signal increased (2.2, 20.9, and 52.3 units; SEM=7.5; P<.005) as follicles progressed from primordial to primary to secondary. In summary, GHR, IGF-IR, IGF-II, IGF-IIR and IGFBP-2 mRNA but not IGF-I mRNA were present within the neonatal pig ovary. The IGF-II and IGFBP-2 mRNA underwent developmental regulation in opposing directions. We conclude that the IGF system may control early phases of ovarian follicular development.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.