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)
Pau
K Y
KY
Division of Reproductive Biology and Behavior, Oregon Regional Primate Research Center, Beaverton 97006.
Gliessman
P M
PM
Hess
D L
DL
Ronnekleiv
O K
OK
Levine
J E
JE
Spies
H G
HG
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