Effect of insulin-like growth factor I on gonadotropin release from the hypothalamus-pituitary axis in vitro.
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 (20-5000 micrograms/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 micrograms/l). In primary cultures of rat anterior pituitary cells, IGF-I (2000 micrograms/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 micrograms/l) did not affect the LH release from the hypothalamus-pituitary or pituitary alone. However, it caused a significant increase in the GnRH (10(-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.
Kanematsu
T
T
Department of Obstetrics and Gynecology, University of Tokushima, School of Medicine, Japan.
Irahara
M
M
Miyake
T
T
Shitsukawa
K
K
Aono
T
T
D000818:Animals; D002478:Cells, Cultured; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000378:metabolism*; D010477:Perfusion; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains
D007334:Insulin-Like Growth Factor I; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone