Administration of insulin-like growth factor I to rhesus monkeys does not augment gonadotropin-stimulated ovarian steroidogenesis.
Although it is well established that IGF-I is able to amplify the actions of FSH and LH on ovarian cells in vitro, little information is available regarding the effects of IGF-I on ovarian function in vivo. To address this question, rhesus monkeys whose spontaneous gonadotropin secretion was interrupted with a GnRH antagonist received continuous iv infusions of saline, IGF-I (240 microg/kg.d), or IGF-I (240 microg/kg.d) plus human GH (hGH) (200 microg/kg.d) 7 d before and continuing throughout a 15-d iv infusion of hFSH and hLH during which serum LH concentrations were maintained at 7-10 mIU/ml and FSH concentrations were incrementally increased every 3 d from 7.5 to 17.5 mIU/ml. Serum estradiol concentrations in saline-treated control animals did not differ (P > 0.05) from animals treated with IGF-I + hGH. In contrast, serum estradiol levels in IGF-I-treated animals were significantly less (P < 0.05) than those of control or IGF-I + hGH-treated animals. Serum androstenedione levels did not differ among the three treatment groups. Analysis of follicular fluids on the final day of gonadotropin infusion indicated that intrafollicular IGF-I concentrations paralleled serum IGF-I concentrations in all treatment groups. Measurement of the ratio of IGF-I to IGF-binding protein-3 in follicular fluids indicated that there was not a disproportionate increase in I-binding protein-3 in animals infused with either IGF-I alone or IGF-I + hGH. Concentrations of GH in follicular fluids of IGF-I treated animals were less than control animals suggesting that the diminished responsiveness of ovaries to FSH in the IGF-I treatment group may have been due to reduced GH.
Zeleznik
Anthony J
AJ
Department of Physiology and Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA. zeleznik@pitt.edu
Little-Ihrig
Lynda
L
Ramasawamy
Suresh
S
D000818:Animals; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000494:pharmacology*; D013006:Growth Hormone / Q000378:metabolism; D006728:Hormones / Q000096:biosynthesis*; D019382:Human Growth Hormone / Q000097:blood / Q000494:pharmacology; D007262:Infusions, Intravenous; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000097:blood / Q000494:pharmacology*; D008253:Macaca mulatta; D010053:Ovary / Q000187:drug effects* / Q000378:metabolism*; D013997:Time Factors
D006728:Hormones; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013006:Growth Hormone