Acute administration of estrogen suppresses LH secretion without altering GnRH release in ovariectomized rhesus macaques.
The pattern of hypothalamic gonadotropin-releasing hormone (GnRH) release was examined during estrogen (E)-induced suppression of plasma luteinizing hormone (LH) in ovariectomized (OVX) rhesus macaques. In Expt. 1, 4 OVX macaques were fitted with a jugular catheter and a push-pull cannula (PPC) directed into the median eminence (ME). Push-pull perfusion (PPP) was initiated 10 h before and continued for 10 h after subcutaneous estradiol benzoate (EB) injection (42 micrograms/kg b.wt.). In Expt. 2, 4 additional monkeys were subjected to local intrahypothalamic perfusion with estradiol-17 beta (E2, 3 microM) for the last 10 h of a 20-h PPP. In Expt. 2, OVX animals were challenged with 5 micrograms exogenous GnRH 3 h before and 8 h after EB injection to test for changes in altered LH release. Integrated 10-min ME perfusate and intermittent 10- or 60-min peripheral plasma samples were assayed for GnRH and LH by radioimmunoassay and bioassay, respectively. In addition, 2 other OVX macaques that received similar ME-PPC placement were sacrificed 2 days after the completion of a PPP for immunocytochemical labeling of GnRH neurons at the perfusion site. The results show that after EB, hypothalamic GnRH (MBH-GnRH) release remained unaltered while LH levels declined rapidly (Expt. 1). Similarly, intrahypothalamic perfusion of E2 failed to change the pattern of MBH-GnRH release in any of 4 monkeys (Expt. 2). Conversely, plasma LH release in response to exogenous GnRH was greatly reduced after EB (Expt. 3).(ABSTRACT TRUNCATED AT 250 WORDS)
Division of Reproductive Biology and Behavior, Oregon Regional Primate Research Center, Beaverton 97006.
K Y
KY
Pau
P M
PM
Gliessman
D L
DL
Hess
O K
OK
Ronnekleiv
J E
JE
Levine
H G
HG
Spies
D000818:Animals; D004958:Estradiol / Q000008:administration & dosage*; D005260:Female; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism*; D008251:Macaca / Q000378:metabolism*; D008253:Macaca mulatta / Q000378:metabolism*; D010052:Ovariectomy; D010906:Pituitary Hormone-Releasing Hormones / Q000378:metabolism*
D010906:Pituitary Hormone-Releasing Hormones; D004958:Estradiol; D007986:Luteinizing Hormone