Ovariectomy-evoked increase in gonadotropin releasing hormone receptor parallels its messenger RNA level, but does not correlate with stimulated gonadotropin release.
The amount of gonadotropin releasing hormone receptor (GnRH-R) in the anterior pituitary changes during the rat estrous cycle; in addition, it is chronically increased for several weeks in response to ovariectomy. The present study was undertaken to investigate these changes in relation to the concentrations of GnRH-R mRNA, gonadotropins and luteinizing hormone-beta (LH-beta) subunit in serum and the pituitary gland, as well as hypothalamic GnRH. GnRH-R concentrations on the day of estrus were significantly lower than that at diestrus (30% lower during 2 d), its mRNA decreased even further (by 60%), but there were no significant changes in gonadotropin. Ovariectomy increased GnRH-R significantly (by 30% during 2 wk) in parallel with receptor mRNA and with pituitary LH and LH-beta, but induced an earlier increase in serum gonadotropins. Our results suggest that transcriptional activity is more intimately linked to the number of GnRH-R in the long-term increase after ovariectomy than in the short-term change during the estrous cycle, and that the increased GnRH-R is not a major factor in ovariectomy-stimulated gonadotropin release.
Saito
S
S
Department of Obstetrics and Gynecology, School of Medicine, Keio University, Tokyo, Japan.
Izumi
S
S
Kobayashi
M
M
Saitoh
S
S
Makino
T
T
Yoshimura
Y
Y
Nozawa
S
S
Takamatsu
K
K
D000818:Animals; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000378:metabolism; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011966:Receptors, LHRH / Q000235:genetics* / Q000378:metabolism*
D006065:Gonadotropins, Pituitary; D012333:RNA, Messenger; D011966:Receptors, LHRH; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone