Insulin-like growth factor-I down-regulates ghrelin receptor (growth hormone secretagogue receptor) expression in the rat pituitary.
The effects of insulin-like growth factor-I (IGF-I) on the ghrelin receptor [growth hormone secretagogue receptor (GHS-R)] gene expression and on the GH response to GHS in rat pituitary cell cultures were examined. Pituitary GHS-R mRNA levels were decreased in a dose (0.01-10 nM)- and time (4-12 h)-dependent manner by IGF-I as measured with reverse transcriptase (RT)-PCR. The basal GH secretion was not influenced by the pretreatment with IGF-I (1 nM for 8 h); however, the GH response to the receptor ligand, a synthetic GHS, KP-102 (100 nM, 15 min), was significantly reduced by pretreatment with IGF-I. Thus, the present studies indicate that IGF-I could inhibit GH secretion at least in part by regulating the expression of the GHS-R.
Kamegai
Jun
J
Department of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-Ku, Tokyo 113-8603, Japan. jkamegai@nms.ac.jp
Tamura
Hideki
H
Shimizu
Takako
T
Ishii
Shinya
S
Sugihara
Hitoshi
H
Oikawa
Shinichi
S
D000818:Animals; D002478:Cells, Cultured; D013006:Growth Hormone / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D054440:Receptors, Ghrelin
D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D054440:Receptors, Ghrelin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone