Insulin-Like Growth Factor Binding Protein -2 and -4 Messenger Ribonucleic Acid Expression in Bovine Ovarian Follicles: Effect of Gonadotropins and Developmental Status

Abstract

This work is concerned with the role of insulin-like growth factor binding protein (IGFBP)-2 and -4 in the regulation of IGF bioactivity in bovine follicles during the development of dominance. We measured the expression of IGFBP-2 and -4 messenger RNA (mRNA) in small (1-4 mm) gonadotropin-sensitive follicles and medium (4-8 mm) and large (>8 mm) gonadotropin-dependent follicles using in situ hybridization. In healthy nonatretic bovine follicles, IGFBP-2 and -4 mRNA expression was confined to granulosa and theca tissue, respectively. Moreover, during the development of follicular atresia, there were distinct changes in the temporal and spatial expression of these genes. IGFBP-2 immunoactivity was localized in granulosa tissue and the basement membrane of healthy preantral follicles, whereas IGFBP-4 immunoactivity was localized in both theca and granulosa tissue. Of particular interest was the lack of IGFBP-2 mRNA expression in large (>8 mm) gonadotropin-dependent follicles, an observation that was confirmed by the lack of immunoreactive IGFBP-2 in these follicles. The regulation of IGFBP-2 and -4 mRNA expression in granulosa and theca cells was analyzed using a serum-free cell culture system. FSH inhibited the expression of IGFBP-2 mRNA in granulosa cells, whereas LH stimulated IGFBP-4 mRNA expression in theca cells. Our results provide evidence for the existence of different roles for IGFBP-2 and -4 in the developing follicle.

Insulin-like growth factors-I and -II and insulin-like growth factor-binding protein-2 in dominant equine follicles during spring transition and the ovulatory season

“…In the present study, IGFBP-2 mRNA was located in both granulosa and theca layers, in contrast to the cow and sheep, where IGFBP-2 mRNA is confined to granulosa cells (Besnard et al 1996, Armstrong et al 1998, but similarly to the pig (Yuan et al 1996) and women (Zhou & Bondy 1993).…”

“…In contrast to the mare, in the cow and sheep the decrease in levels of IGFBP-2 during follicle growth is due largely to a loss of expression of mRNA encoding IGFBP-2 in the granulosa cells of dominant follicles (Besnard et al 1996, Armstrong et al 1998. One explanation of the discrepancy between message and protein in the mare would be the presence of IGFBP-2 protease activity in follicular fluid of preovulatory follicles.…”

“…Plasmids containing cDNAs for bovine IGFBP-2, IGF-I and IGF-II were linearized as described previously (Armstrong et al 1998). Antisense and sense [ 35 S]UTP-labelled cRNA probes were transcribed from these templates with a transcription kit (Promega Ltd, Southampton, UK) according to the manufacturer's instructions.…”

Effects of IGF-I bioavailability on bovine preantral follicular development in vitro

“…A proportion of follicles fixed on day 6 of culture (nZ10 follicles) was randomly selected and used for detection of IGFBP-2 immunoreactivity using the method described by Armstrong et al (1998), with some modifications. Follicles were fixed in 4% paraformaldehyde, embedded in paraffin wax and sectioned (6 mm).…”

Insulin-Like Growth Factor-I as a Possible Hormonal Mediator of Nutritional Regulation of Reproduction in Cattle

“…Inhibition of IGFBP expression by gonadotropins is one mechanism by which IGFBPs of low molecular weight are decreased in preovulatory follicular fluid [4,39,62,75,77]. In rats, Liu et al [52] showed that expression of mRNAs encoding IGFBP-4 and 5 decreased in FSH stimulated granulosa cells in vitro.…”