Effect of insulin-like growth factor 1 on gonadotropin release from the hypothalamus-pituitary axis in vitro

Abstract

The effects of insulin-like growth factor-I on gonadotropin release were studied using primary culture of rat anterior pituitary cells incubated with IGF-I ( 20\ x=r eq-\ 5000 \g=m\g/l) and a hypothalamus-pituitary perifusion system, in which either the mediobasal hypothalamus-pituitary unit or the pituitary were perifused with IGF-I (20-2000 \g=m\g/l). In primary cultures of rat anterior pituitary cells, IGF-I (2000 \g=m\g/l ) caused a significant increase in the release of both LH (46% increase) and FSH (27% increase). It also caused a significant decrease in the cellular content of LH (9%) and FSH (19%). Its effects in stimulating gonadotropin release were suppressed by administration of anti IGF-I receptor antibody (1 mg/l). In the perifusion system, IGF-I (2000 \g=m\g/l ) did not affect the LH release from the hypothalamus-pituitary or pituitary alone. However, it caused a significant increase in the GnRH (10\ m=-\ 9 mol/l) stimulated LH release from perifused pituitary. These data suggest that IGF-I enhances pituitary gonadotropin release via the IGF-I receptor, but its effect on the hypothalamus was not confirmed.

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

“…Adam et al [1] reported that an increase in circulatory IGF-I within the physiological range stimulates LH secretion in sheep. Kanematsu et al [48] after incubation of rat pituitary cells with IGF-I at a concentration of 2,000 and 5,000 µg/L for 72 hr, found that IGF-I increased the release of LH and FSH significantly from the cells in a dose dependent manner. Their study however found no significant change in LH release from an IGF-I perfused hypothalamus-pituitary unit or pituitary alone, suggesting that IGF-I may not have a strong effect on GnRH release from the hypothalamus.…”

Hypophysiotropic role of RFamide-related peptide-3 in the inhibition of LH secretion in female rats

“…25% trypsin, followed by dissociation performed by pipetting 0 . 2% pancreatin at 37 8C for 1 min, as has been previously reported (Kanematsu et al 1991, Tezuka et al 2002. Pituitary cells were seeded in DMEM containing 10% fetal bovine serum, and then plated on 24-well culture dishes (Falcon Plastics, Los Angeles, CA, USA) at a density of 10 6 viable cells/well.…”

Molecular Regulation of Gonadotropin Secretion by Gonadotropin Releasing Hormone in Salmonid Fishes

“…For example, intraventricular administration of IGF-I in female rats increased plasma luteinizing hormone (LH) and advanced the onset of puberty (Hiney et al, 1996). The administration of IGF-I to rat pituitary cell cultures increased basal secretion of follicle-stimulating hormone (FSH) and LH and gonadotropin-releasing hormone (GnRH)-induced LH secretion (Kanematsu, et al, 1991;Soldani et al, 1994Soldani et al, , 1995Xia et al, 2001). Moreover, in male rats, IGF-I stimulated release of FSH and LH, with increased expression of the glycoprotein α (GPα) subunit gene but not of the FSHβ, nor LHβ subunit genes (Pazos et al, 2004).…”