Localization of binding sites for IGF-I, insulin and GH in the sow ovary

Abstract

Binding sites for IGF-I, insulin, and GH were localized by in situ binding of 125 I-labelled hormones to the different compartments of the sow ovary. Binding sites for IGF-I were detected in oocytes, granulosa and thecal cells of healthy and atretic follicles as well as in the antrum and the stroma. Competition of 125 I-labelled IGF-I with IGF-I, insulin and an analogue of IGF-I (Long R 3 IGF-I), which allowed discrimination between binding to binding proteins from binding to type-I receptors, suggested that type-I receptors were present in granulosa cells of healthy follicles, whilst binding in other compartments was mainly due to binding proteins. Binding of insulin was revealed in oocytes, granulosa and theca interna cells of healthy preantral and antral follicles, and, to a lesser extent, in theca externa and stromal cells, and was still observed in granulosa cells of atretic follicles. Labelling with 125 Ilabelled bovine GH was demonstrated in oocytes, granulosa cells, theca interna cells, and, although less intense, in theca externa and stromal cells. It disappeared in granulosa cells during atresia. Binding sites for GH were detected at all follicular stages, from preantral to preovulatory stages, but the intensity of labelling in granulosa cells was more intense in preantral than in large follicles. These data support the participation of insulin, GH and IGF-I in oocyte maturation, follicular growth and stromal cell function in swine.

Regulation of adiponectin and its receptors in rat ovary by human chorionic gonadotrophin treatment and potential involvement of adiponectin in granulosa cell steroidogenesis

“…Adiponectin possesses insulin-sensitizing actions (Kadowaki & Yamauchi 2005). Insulin receptors or corresponding mRNAs have been identified in human or swine ovary in stromal, granulosa and theca cells but also in growing follicles (Poretsky et al 1985, el-Roeiy et al 1993, Samoto et al 1993, Quesnel 1999. A role for insulin has been described in porcine oocyte maturation (Tsafriri & Channing 1975).…”

Growth hormone: roles in female reproduction

“…2), since GH-binding activity peaks during early folliculogenesis in porcine follicles (Quesnel 1999) and fish ovarian Figure 1 Effects of GH in the female reproductive system. Pituitary GH stimulates the production of hepatic IGF-I, and both pituitary GH and hepatic IGF-I act to stimulate mammary, ovarian, uterine and/or oviduct function.…”

“…2), since both GH and gonadotrophins are required to prevent atresia of larger follicles (>2 mm) following hypophysectomy in sheep (Eckery et al 1997). GH may play a role in follicle selection, since GH-binding sites in sow granulosa cells are lost in atretic follicles (Quesnel 1999) and the development of the dominant follicle is impaired in GHRdeficient cattle (Chase et al 1998). GH administration in vivo similarly increases the number of large follicles in pigs (DeLaSota et al 1993 and GH-deficient dwarf rats (Ozawa et al 1996) and the number of corpora lutea in cattle (Lucy et al 1992) and GH transgenic rats (Danilovich et al 2000).…”

GH and IGF-I binding sites in adipose tissue, liver, skeletal muscle and ovaries of feed-restricted gilts

“…However, cell-specific alterations cannot be excluded since GH and IGF-I binding sites are widely distributed within porcine ovaries [26].…”