Abstract
The positive feedback role of estrogen in facilitating the ovulatory discharge of LH has been investigated. It has been shown that estrogen secretion increases in 4-day cyclic rats sometime late in diestrus-2 or early proestrus and reaches peak concentrations at 1000 hours proestrus. LH release begins at 1400 hours and peaks at 1600 hours. Simultaneous with changes in estrogen, peripheral plasma progesterone, of adrenal origin, exhibits diurnal rhythms being elevated between 0100-0500 hours, decreasing to nadir at 1400-1600 hours each day. Consequently, since both sex steroids' plasma levels are fluctuating prior to the ovulatory LH surge, the ratio of estrogen/progesterone may prove to be more important in altering the hypothalamic thresholds of excitability required for LH release than estrogen acting alone. Four-day cyclic rats were ovariectomized (ovx) and/or adrenalectomized (adx) on diestrus-2 at 1000 hours. In ovx rats, replacement of endogenous estrogen by injection of 10 μg 17β-estradiol (E2) resulted in a more or less normal LH surge at proestrus. When progesterone was administered to such ovxestrogen-primed rats, at 0930 hours proestrus, the timing of the LH surge was synchronized, and all rats exhibited peak LH values at 1400 hours. Ovx-adx rats treated with E2 failed to release LH and only did so if estrogen were combined with progesterone. It is suggested from these studies that, in the rat, both steroids, acting synergistically, are essential for the ovulatory LH surge to occur.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 209-222 |
| Number of pages | 14 |
| Journal | Advances in the Biosciences |
| Volume | 15 |
| Issue number | C |
| State | Published - 1975 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Medicine(all)
Cite this
Regulatory role of estrogen in the ovulatory discharge of luteinizing hormone. / Barraclough, Charles A.; Turgeon, Judith L; Cramer, Oneida; Mann, David.
In: Advances in the Biosciences, Vol. 15, No. C, 1975, p. 209-222.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Regulatory role of estrogen in the ovulatory discharge of luteinizing hormone
AU - Barraclough, Charles A.
AU - Turgeon, Judith L
AU - Cramer, Oneida
AU - Mann, David
PY - 1975
Y1 - 1975
N2 - The positive feedback role of estrogen in facilitating the ovulatory discharge of LH has been investigated. It has been shown that estrogen secretion increases in 4-day cyclic rats sometime late in diestrus-2 or early proestrus and reaches peak concentrations at 1000 hours proestrus. LH release begins at 1400 hours and peaks at 1600 hours. Simultaneous with changes in estrogen, peripheral plasma progesterone, of adrenal origin, exhibits diurnal rhythms being elevated between 0100-0500 hours, decreasing to nadir at 1400-1600 hours each day. Consequently, since both sex steroids' plasma levels are fluctuating prior to the ovulatory LH surge, the ratio of estrogen/progesterone may prove to be more important in altering the hypothalamic thresholds of excitability required for LH release than estrogen acting alone. Four-day cyclic rats were ovariectomized (ovx) and/or adrenalectomized (adx) on diestrus-2 at 1000 hours. In ovx rats, replacement of endogenous estrogen by injection of 10 μg 17β-estradiol (E2) resulted in a more or less normal LH surge at proestrus. When progesterone was administered to such ovxestrogen-primed rats, at 0930 hours proestrus, the timing of the LH surge was synchronized, and all rats exhibited peak LH values at 1400 hours. Ovx-adx rats treated with E2 failed to release LH and only did so if estrogen were combined with progesterone. It is suggested from these studies that, in the rat, both steroids, acting synergistically, are essential for the ovulatory LH surge to occur.
AB - The positive feedback role of estrogen in facilitating the ovulatory discharge of LH has been investigated. It has been shown that estrogen secretion increases in 4-day cyclic rats sometime late in diestrus-2 or early proestrus and reaches peak concentrations at 1000 hours proestrus. LH release begins at 1400 hours and peaks at 1600 hours. Simultaneous with changes in estrogen, peripheral plasma progesterone, of adrenal origin, exhibits diurnal rhythms being elevated between 0100-0500 hours, decreasing to nadir at 1400-1600 hours each day. Consequently, since both sex steroids' plasma levels are fluctuating prior to the ovulatory LH surge, the ratio of estrogen/progesterone may prove to be more important in altering the hypothalamic thresholds of excitability required for LH release than estrogen acting alone. Four-day cyclic rats were ovariectomized (ovx) and/or adrenalectomized (adx) on diestrus-2 at 1000 hours. In ovx rats, replacement of endogenous estrogen by injection of 10 μg 17β-estradiol (E2) resulted in a more or less normal LH surge at proestrus. When progesterone was administered to such ovxestrogen-primed rats, at 0930 hours proestrus, the timing of the LH surge was synchronized, and all rats exhibited peak LH values at 1400 hours. Ovx-adx rats treated with E2 failed to release LH and only did so if estrogen were combined with progesterone. It is suggested from these studies that, in the rat, both steroids, acting synergistically, are essential for the ovulatory LH surge to occur.
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UR - http://www.scopus.com/inward/citedby.url?scp=0016415948&partnerID=8YFLogxK
M3 - Article
C2 - 1172472
AN - SCOPUS:0016415948
VL - 15
SP - 209
EP - 222
JO - Advances in the Biosciences
JF - Advances in the Biosciences
SN - 0065-3446
IS - C
ER -