The control of progesterone secretion during the estrous cycle and early pseudopregnancy in the rat: prolactin, gonadotropin and steroid levels associated with rescue of the corpus luteum of pseudopregnancy

M (Susan) Smith, M. E. Freeman, J. D. Neill

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1055 Citations (Scopus)

Abstract

The hormonal factors associated with converting a corpus luteum of estrous cycle into a corupus luteum of pseudopregnancy were studied by measuring luteinising hormone, follice stimulating hormone (LH, FSH) prolactin, estradiol and progesterone levels in decapitated rats during the 4 day estrous cycle and a comparable time of pseudopregnancy (lights on 0600-0800 hr). During the estrous cycle, prolactin, LH and FSH remained low and unchanging excep on the afternoon of proestrus, when typical proestrous surges were oserved. In contrast, estradiol levels began to increase on day 1, from baseline values of 7 pg/ml to approximately 15-20 pg/ml. These levels were maintained until the afternoon of day 2, when estradiol further increased to reach peak levels of 40-50 pg/ml by 0900 hr on proestrus. Estradiol then declined in relation to the increase in LH secretion and had returned to baseline by estrus. Progesterone secretion by the corpora lutea of the cycle also increased on the afternoon of day 1 and reached a maximum value of 25-30 ng/ml early on the morning of day 2. At this time, a precipitous fall in progesterone occurred, returning to baseline values of 5-10 ng/ml by 0700 on day 2, signifying the regression of the corpora lutea of the cycle. Progesterone remained low thereafter until the afternoon of proestrus when levels increased in response to the proestrous surge of LH. Following cervical stimulation at 1900 hr on proestrus, no differences were noted, with respect to the estrous cycle, in LH, FSH or estradiol secretion through the afternoon of day 2. Surprisingly, progesterone levels did not differ in the cycle and psueodopregnancy until the early morning of day 2. Instead of progesterone levels falling to baseline as they had during the cycle, the corpora lutea of pseudopregnancy were rescued, progesterone increasing dramatically to reach levels of 45-50 ng/ml by 1700 hr on that same day. The only difference in hormone secretion that was noted which could account for this marked divergence in progesterone secretion was the pattern of prolactin secretion following cervical stimulation. In contrast to the low levels seen during the estrous cycle, biphasic surges of prolactin secretion occurred each day, one being nocturnal (0100-0900 hr) and the other diurnal (1500-2100 hr). The rescue of the corpus luteum occurred in association with the nocturnal surge on day 2. These results suggest that prolactin is the major luteotropic stimulus which transforms an estrous cycle into a pseudopregnancy by prolonging progesterone secretion from the corpus luteum. Moreover, if LH is important for progesterone secretion, no changes were observed in the pattern of LH secretion which can account for the rescue of the corpus luteum.

Original languageEnglish (US)
Pages (from-to)219-226
Number of pages8
JournalEndocrinology
Volume96
Issue number1
StatePublished - 1975
Externally publishedYes

Fingerprint

Pseudopregnancy
Estrous Cycle
Corpus Luteum
Gonadotropins
Prolactin
Progesterone
Steroids
Proestrus
Estradiol
Hormones
Luteinizing Hormone
Luteolysis
Estrus

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

@article{f1936e06a4464540ab58ba7f139bb234,
title = "The control of progesterone secretion during the estrous cycle and early pseudopregnancy in the rat: prolactin, gonadotropin and steroid levels associated with rescue of the corpus luteum of pseudopregnancy",
abstract = "The hormonal factors associated with converting a corpus luteum of estrous cycle into a corupus luteum of pseudopregnancy were studied by measuring luteinising hormone, follice stimulating hormone (LH, FSH) prolactin, estradiol and progesterone levels in decapitated rats during the 4 day estrous cycle and a comparable time of pseudopregnancy (lights on 0600-0800 hr). During the estrous cycle, prolactin, LH and FSH remained low and unchanging excep on the afternoon of proestrus, when typical proestrous surges were oserved. In contrast, estradiol levels began to increase on day 1, from baseline values of 7 pg/ml to approximately 15-20 pg/ml. These levels were maintained until the afternoon of day 2, when estradiol further increased to reach peak levels of 40-50 pg/ml by 0900 hr on proestrus. Estradiol then declined in relation to the increase in LH secretion and had returned to baseline by estrus. Progesterone secretion by the corpora lutea of the cycle also increased on the afternoon of day 1 and reached a maximum value of 25-30 ng/ml early on the morning of day 2. At this time, a precipitous fall in progesterone occurred, returning to baseline values of 5-10 ng/ml by 0700 on day 2, signifying the regression of the corpora lutea of the cycle. Progesterone remained low thereafter until the afternoon of proestrus when levels increased in response to the proestrous surge of LH. Following cervical stimulation at 1900 hr on proestrus, no differences were noted, with respect to the estrous cycle, in LH, FSH or estradiol secretion through the afternoon of day 2. Surprisingly, progesterone levels did not differ in the cycle and psueodopregnancy until the early morning of day 2. Instead of progesterone levels falling to baseline as they had during the cycle, the corpora lutea of pseudopregnancy were rescued, progesterone increasing dramatically to reach levels of 45-50 ng/ml by 1700 hr on that same day. The only difference in hormone secretion that was noted which could account for this marked divergence in progesterone secretion was the pattern of prolactin secretion following cervical stimulation. In contrast to the low levels seen during the estrous cycle, biphasic surges of prolactin secretion occurred each day, one being nocturnal (0100-0900 hr) and the other diurnal (1500-2100 hr). The rescue of the corpus luteum occurred in association with the nocturnal surge on day 2. These results suggest that prolactin is the major luteotropic stimulus which transforms an estrous cycle into a pseudopregnancy by prolonging progesterone secretion from the corpus luteum. Moreover, if LH is important for progesterone secretion, no changes were observed in the pattern of LH secretion which can account for the rescue of the corpus luteum.",
author = "Smith, {M (Susan)} and Freeman, {M. E.} and Neill, {J. D.}",
year = "1975",
language = "English (US)",
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pages = "219--226",
journal = "Endocrinology",
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T1 - The control of progesterone secretion during the estrous cycle and early pseudopregnancy in the rat

T2 - prolactin, gonadotropin and steroid levels associated with rescue of the corpus luteum of pseudopregnancy

AU - Smith, M (Susan)

AU - Freeman, M. E.

AU - Neill, J. D.

PY - 1975

Y1 - 1975

N2 - The hormonal factors associated with converting a corpus luteum of estrous cycle into a corupus luteum of pseudopregnancy were studied by measuring luteinising hormone, follice stimulating hormone (LH, FSH) prolactin, estradiol and progesterone levels in decapitated rats during the 4 day estrous cycle and a comparable time of pseudopregnancy (lights on 0600-0800 hr). During the estrous cycle, prolactin, LH and FSH remained low and unchanging excep on the afternoon of proestrus, when typical proestrous surges were oserved. In contrast, estradiol levels began to increase on day 1, from baseline values of 7 pg/ml to approximately 15-20 pg/ml. These levels were maintained until the afternoon of day 2, when estradiol further increased to reach peak levels of 40-50 pg/ml by 0900 hr on proestrus. Estradiol then declined in relation to the increase in LH secretion and had returned to baseline by estrus. Progesterone secretion by the corpora lutea of the cycle also increased on the afternoon of day 1 and reached a maximum value of 25-30 ng/ml early on the morning of day 2. At this time, a precipitous fall in progesterone occurred, returning to baseline values of 5-10 ng/ml by 0700 on day 2, signifying the regression of the corpora lutea of the cycle. Progesterone remained low thereafter until the afternoon of proestrus when levels increased in response to the proestrous surge of LH. Following cervical stimulation at 1900 hr on proestrus, no differences were noted, with respect to the estrous cycle, in LH, FSH or estradiol secretion through the afternoon of day 2. Surprisingly, progesterone levels did not differ in the cycle and psueodopregnancy until the early morning of day 2. Instead of progesterone levels falling to baseline as they had during the cycle, the corpora lutea of pseudopregnancy were rescued, progesterone increasing dramatically to reach levels of 45-50 ng/ml by 1700 hr on that same day. The only difference in hormone secretion that was noted which could account for this marked divergence in progesterone secretion was the pattern of prolactin secretion following cervical stimulation. In contrast to the low levels seen during the estrous cycle, biphasic surges of prolactin secretion occurred each day, one being nocturnal (0100-0900 hr) and the other diurnal (1500-2100 hr). The rescue of the corpus luteum occurred in association with the nocturnal surge on day 2. These results suggest that prolactin is the major luteotropic stimulus which transforms an estrous cycle into a pseudopregnancy by prolonging progesterone secretion from the corpus luteum. Moreover, if LH is important for progesterone secretion, no changes were observed in the pattern of LH secretion which can account for the rescue of the corpus luteum.

AB - The hormonal factors associated with converting a corpus luteum of estrous cycle into a corupus luteum of pseudopregnancy were studied by measuring luteinising hormone, follice stimulating hormone (LH, FSH) prolactin, estradiol and progesterone levels in decapitated rats during the 4 day estrous cycle and a comparable time of pseudopregnancy (lights on 0600-0800 hr). During the estrous cycle, prolactin, LH and FSH remained low and unchanging excep on the afternoon of proestrus, when typical proestrous surges were oserved. In contrast, estradiol levels began to increase on day 1, from baseline values of 7 pg/ml to approximately 15-20 pg/ml. These levels were maintained until the afternoon of day 2, when estradiol further increased to reach peak levels of 40-50 pg/ml by 0900 hr on proestrus. Estradiol then declined in relation to the increase in LH secretion and had returned to baseline by estrus. Progesterone secretion by the corpora lutea of the cycle also increased on the afternoon of day 1 and reached a maximum value of 25-30 ng/ml early on the morning of day 2. At this time, a precipitous fall in progesterone occurred, returning to baseline values of 5-10 ng/ml by 0700 on day 2, signifying the regression of the corpora lutea of the cycle. Progesterone remained low thereafter until the afternoon of proestrus when levels increased in response to the proestrous surge of LH. Following cervical stimulation at 1900 hr on proestrus, no differences were noted, with respect to the estrous cycle, in LH, FSH or estradiol secretion through the afternoon of day 2. Surprisingly, progesterone levels did not differ in the cycle and psueodopregnancy until the early morning of day 2. Instead of progesterone levels falling to baseline as they had during the cycle, the corpora lutea of pseudopregnancy were rescued, progesterone increasing dramatically to reach levels of 45-50 ng/ml by 1700 hr on that same day. The only difference in hormone secretion that was noted which could account for this marked divergence in progesterone secretion was the pattern of prolactin secretion following cervical stimulation. In contrast to the low levels seen during the estrous cycle, biphasic surges of prolactin secretion occurred each day, one being nocturnal (0100-0900 hr) and the other diurnal (1500-2100 hr). The rescue of the corpus luteum occurred in association with the nocturnal surge on day 2. These results suggest that prolactin is the major luteotropic stimulus which transforms an estrous cycle into a pseudopregnancy by prolonging progesterone secretion from the corpus luteum. Moreover, if LH is important for progesterone secretion, no changes were observed in the pattern of LH secretion which can account for the rescue of the corpus luteum.

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