Effect of Hysterectomy on Serum Luteinizing Hormone Concentrations and on Corpus Luteum Function in the Rat

Greef, W. J. De; Dullaart, J.; Zeilmaker, G. H.

doi:10.1210/endo-98-5-1228

Cited by 24 publications

(13 citation statements)

References 21 publications

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“…Hysterectomy lowered serum LH concentrations in the pseudopregnant and the ovariectomized rats [4], increased suckling-induced PRL secretion and caused the disappearance of the diurnal PRL surges in lactating rats [15], without affecting the preovulatory LH [4] and PRL surge. Taken together with the high OTR mRNA levels observed in the afternoon of proestrus, oxytocin might be involved in the regulation of LH and/or PRL secretion through the uterus after their preovulatory surges.…”

Section: Discussionmentioning

confidence: 93%

Changes of Receptor mRNAs for Oxytocin and Estrogen during the Estrous Cycle in Rat Uterus

Murata

Narita

Honda

et al. 2003

The Journal of Veterinary Medical Science

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ABSTRACT. Oxytocin receptor (OTR) mRNA levels increase dramatically near term and is potently stimulated by estrogen because increased OTR mRNA levels result from estrogen treatment in ovariectomized rat uterus. In this study, OTR, estrogen receptor (ER) α and ERβ mRNA levels in the rat uterus during the estrous cycle were examined by quantitative RT-PCR. OTR mRNA levels during the estrous cycle began to increase on diestrus (P<0.05, vs value on estrus), reached maximal increase both in the morning (1000-1130 hr) and afternoon (1600-1630 hr) on proestrus (P<0.01, vs metestrus, diestrus and estrus) and then declined on estrus. In contrast ERα mRNA levels began to decrease on diestrus, reached statistical significance both in the morning and the afternoon on proestrus (P<0.01, vs metestrus, diestrus and estrus) and returned to the value of metestrus on estrus. ERβ mRNA levels were low in the morning and the afternoon on proestrus (P<0.01, vs metestrus and estrus) and also returned to metestrus values on estrus. Treatments with estrogen for 3 days significantly decreased both ERα and ERβ mRNA levels. It can be concluded from these results that during the estrous cycle, OTR mRNA levels in rat uterus predominantly increase at proestrus with a decrease in ERα and ERβ mRNA levels, which is probably due to the increased estrogen levels in circulation before ovulation. KEY WORDS: estrogen receptor, estrous cycle, oxytocin receptor, rat.J. Vet. Med. Sci. 65(6): 707-712, 2003 Oxytocin (OT) was initially isolated as a neurohypophysial hormone which stimulates the contraction of the myometrium and myoepithelium to facilitate parturition and milk ejection respectively, and is considered to act on various reproductive functions in the ovary, the uterus or the brain. In the uterus, the near-term myometrium is extremely sensitive to oxytocin and this increased uterine responsiveness to oxytocin occurs in parallel with an increase in the number of uterine oxytocin binding sites in rats [6,40], humans [7], rabbits [22,23] and cows [9]. Corresponding increases in uterine oxytocin receptor (OTR) mRNA expression in late pregnancy and parturition have been reported in cows [12], rats [20,21,31], humans [17] and sheep [50,52].Estrogen stimulates the number of uterine oxytocin binding sites [6,38,41] and OTR mRNA expression in ovariectomized (OVX) virgin rats [20,21]. However, injection of estrogen does not stimulate oxytocin receptor mRNA expression in late pregnant rats or in progesterone-primed OVX virgin rats, but is effective only after ovariectomy and removal of progesterone, respectively [27]. These results suggest that, in addition to the increase in serum estrogen level near term in rats, regulation of the uterine responsiveness to estrogen is important for understanding the role of estrogen in the uterus. The actions of estrogen are mediated through transcription-regulating intracellular estrogen receptors [1,30]. Two types of estrogen receptor (ER), ERα and ERβ have been cloned from human uterus [11] and rat prostate [19] ...

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Section: Discussionmentioning

confidence: 93%

Changes of Receptor mRNAs for Oxytocin and Estrogen during the Estrous Cycle in Rat Uterus

Murata

Narita

Honda

et al. 2003

The Journal of Veterinary Medical Science

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“…Removal of the uterus in pseudopregnant rats prolongs the activity of the corpus luteum [16,27] and prolongs the occurrence of the PRL surges [7,13].…”

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confidence: 99%

Effect of Lesions of the Corticomedial Amygdala on the Nocturnal Prolactin Surge

Clarke

Gala

1985

Neuroendocrinology

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It has been reported that the corticomedial amygdala (CMA) is involved in regulating various hypothalamic and neuroendocrine events. This study examined the role of the CMA in the regulation of the nocturnal surge of prolactin (PRL) induced by cervical stimulation (CS). Female Sprague-Dawley rats were ovariectomized, received CMA or sham lesions, and were placed on a reversed lighting schedule of 14 h light: 10 h dark. 3 weeks later, all rats were cervically stimulated. 5 days after CS (CS + 5) rats were fitted with chronic, intraatrial catheters, and daily progesterone (P) injections (10 mg s.c.) were initiated. On CS + 8, CS + 12, and CS + 15, sequential blood samples were taken from unrestrained rats at 00.00, 02.00, 04.00, 06.00, 08.00, and 10.00 h (animal time). CMA lesions significantly reduced peak PRL levels on CS + 12 and CS+ 15, but not on CS + 8. When ovariectomized CS rats received either 1 or 10 mg P/day and were sampled on CS+ 12, CS+ 15, and CS + 19, CMA lesions reduced the magnitude of the surge on CS+ 12 and CS + 15, a time when P amplification of the surge was apparent. On CS+ 19, when P amplification of the surge was absent, CMA lesions had no effect. CMA lesions greatly reduced peak PRL levels on CS + 12, but not on CS + 8, when rats were lesioned, catheterized, and injected daily with 1 or 10 mg P/day on CS + 3. Similar results were seen in CS rats with their ovaries intact. CMA lesions reduced the magnitude of the nocturnal PRL surge on CS + 12, but not on CS + 8, in pseudopregnant rats that were given 2 mg P/day, in addition to their ovarian P secretion, to extend the occurrence of the surge through CS+ 12. Since lesions of the CMA resulted in blocking the extension of the amplitude of the nocturnal surge, it is suggested that the CMA may play a role in the termination process of the surge. The CMA may mediate at least part of the action of P to delay termination of the surge.

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“…Changes in hemodynamics, renal function and volume homeostasis as well as endocrine changes do not differ appreciably between early pseudo -and early normal rat pregnancy [1,2,7,16,19,21,22]. Therefore, the pseudopregnant rat seems to be an attractive model to explore the mechanism of early-pregnancy vasodilatation.…”

Section: Discussionmentioning

confidence: 99%

“…The latter induces a state of prolonged pseudopregnancy, in which the hormonal changes do not differ appreciably from those in normal pregnancy as well as from those in pseudopregnancy [7,16]. The present study was designed to test the hypothesis that the hemodynamic changes in early pseudopregnancy develop exclusively in response to changes in the circulating levels of ovarian hormones.…”

Section: Introductionmentioning

confidence: 98%

“…Meanwhile, in the rat the state of pseudopregnancy mimics early pregnancy in many aspects. Pseudopregnancy in the rat is a condition characterized by the persistence of the endocrine function of the corpus luteum and lasts for a period of up to 12-14 days [1,7]. During the first 9-10 days of this period, the patterns of change in the circulating levels of the sex steroids and prolactin [1,8,11,22] on the one hand, and those in hemodynamics on the other hand [15,20] are comparable with those in normal early rat pregnancy.…”

Section: Introductionmentioning

confidence: 99%

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Hemodynamic changes in pseudopregnancy in chronically instrumented, conscious rats are preserved after hysterectomy

Eijndhoven

Slangen

Heijden

et al. 2002

Pflugers Arch - Eur J Physiol

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Hemodynamic changes in early-pregnant and pseudopregnant rats are comparable, indicating that the trophoblast does not contribute to these changes. It is unclear whether the presence of the uterus is needed for the normal early-pregnancy hemodynamic adaptation. In this study we tested the hypothesis that uterine factors do not contribute to the systemic hemodynamic changes in early pseudopregnancy. To this end, we studied systemic hemodynamics in conscious pseudopregnant rats subjected to a hysterectomy, and compared these results with those obtained in a control group of pseudopregnant rats. The animals were studied on days 4, 8, 12 and 19 postmating. On day 8 of pseudopregnancy, cardiac output has increased by 23+/-7% in the hysterectomized group and 15+/-5% in the control group. In both groups this rise in cardiac output was entirely accomplished by a rise in stroke volume, by 28+/-8% and 19+/-5%, respectively. Mean arterial pressure did not change appreciably. Therefore, total peripheral resistance also decreased in both groups (17+/-6%) by day 8. After day 12 the hemodynamic parameters returned to baseline. We conclude that systemic hemodynamic changes in hysterectomized pseudopregnant rats closely resemble those in intact pseudopregnant rats. Therefore, the uterus does not seem to play a role in these changes. This supports the hypothesis that only hormones from ovarian origin trigger the initial hemodynamic adaptation to early pregnancy.

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Effect of Hysterectomy on Serum Luteinizing Hormone Concentrations and on Corpus Luteum Function in the Rat

Cited by 24 publications

References 21 publications

Changes of Receptor mRNAs for Oxytocin and Estrogen during the Estrous Cycle in Rat Uterus

Changes of Receptor mRNAs for Oxytocin and Estrogen during the Estrous Cycle in Rat Uterus

Effect of Lesions of the Corticomedial Amygdala on the Nocturnal Prolactin Surge

Hemodynamic changes in pseudopregnancy in chronically instrumented, conscious rats are preserved after hysterectomy

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