PMID- 233935
OWN - NLM
STAT- MEDLINE
DCOM- 19750609
LR  - 20181203
IS  - 0013-7227 (Print)
IS  - 0013-7227 (Linking)
VI  - 96
IP  - 3
DP  - 1975 Mar
TI  - Acute and chronic estradiol-17beta inhibition of LH release in prepubertal female 
      pigs: time course and site of action.
PG  - 558-63
AB  - It has been demonstrated that 5.0 mug estradiol-17beta (E2) iv inhibits 
      spontaneous episodic release (SER) of LH from 3-9 h after injection in immature 
      female pigs (gilts). To understand this phenomenon we tested pituitary response 
      (PR) to synthetic LH-RH/FSH-RH (LH-RH) for 13 h after identical E2 treatment in 
      eight 7-8-week-old gilts. Using chronic cannulae PR was determined by measuring 
      the change in plasma LH (delta LH) by RIA after iv injection of 2.0 mug LH-RH. PR 
      was determined every 2 h starting 1 or 2 h before E2 or saline treatments. The PR 
      prior to treatment was 4.3 plus or minus 0.3 ng/ml. By the second 
      releasing-hormone challenge PR in controls was depressed, remaining at about 2.5 
      ng/ml thereafter. Compared with controls PR depression was greater (P less than 
      0.005) 1 h following E2 (delta LH = 1.0 plus or minus 0.4 ng/ml). Responsiveness 
      then returned toward pretreatment levels and from 6 h post-treatment onward PR 
      was not different from controls. Initial inhibition of SER may therefore be 
      located in the pituitary and brain. However, after 4 h inhibition appears to be 
      purely neural. Earlier studies showed that subcutaneous (SC) implants of E2 for 3 
      days in prepubertal gilts depressed PR to LH-RH. We further examined the effect 
      upon PR of implants releasing physiologic levels of E2. PR was evaluated as above 
      at 2-h intervals for 12 h after SC implantation of silastic capsules containing 
      E2 (n = 6) or sham implant (n = 1); then every 6 h up to 54 h post-treatment. For 
      the first 12 h PR depression in the control was identical to controls in the 
      acute experiment; after 36 h PR was similar to pretreatment levels. In E2 
      implanted animals PR fell to a mean of 1.8 plus or minus 0.1 ng/ml, 4-12 h after 
      implantation, then recovered, stabilizing at 2.3 plus or minus 0.1 ng/ml after 18 
      h. It is concluded that estrogen treatment rapidly causes a depression of 
      pituitary response to exogenous LH-RH. This rapid effect may not be dependent on 
      E2 dosage. The extent of recovery of pituitary responsiveness probably depends 
      upon the level and persistence of the E2 treatment.
FAU - Pomerantz, D K
AU  - Pomerantz DK
FAU - Foxcroft, G R
AU  - Foxcroft GR
FAU - Nalbandov, A V
AU  - Nalbandov AV
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Endocrinology
JT  - Endocrinology
JID - 0375040
RN  - 33515-09-2 (Gonadotropin-Releasing Hormone)
RN  - 4TI98Z838E (Estradiol)
RN  - 9002-67-9 (Luteinizing Hormone)
SB  - IM
MH  - Animals
MH  - Depression, Chemical
MH  - Dose-Response Relationship, Drug
MH  - Estradiol/*pharmacology
MH  - Female
MH  - Gonadotropin-Releasing Hormone/pharmacology
MH  - Luteinizing Hormone/blood/*metabolism
MH  - Pituitary Gland/*metabolism
MH  - Radioimmunoassay
MH  - Swine
MH  - Time Factors
EDAT- 1975/03/01 00:00
MHDA- 1975/03/01 00:01
CRDT- 1975/03/01 00:00
PHST- 1975/03/01 00:00 [pubmed]
PHST- 1975/03/01 00:01 [medline]
PHST- 1975/03/01 00:00 [entrez]
AID - 10.1210/endo-96-3-558 [doi]
PST - ppublish
SO  - Endocrinology. 1975 Mar;96(3):558-63. doi: 10.1210/endo-96-3-558.