Steroidogenic Effect of 170-Estradiol in the Rabbit: Stimulation of Progesterone Synthesis in Prematurely Regressing Corpora Lutea*

Bender, Edward M.; Miller, Josephine B.; Possley, R. M.; Keyes, P. Landis

doi:10.1210/endo-103-5-1937

Cited by 45 publications

(13 citation statements)

References 21 publications

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“…The day of hCG injection (day of ovulation) was designated as Day 0. On Day 1 of pseudopregnancy, all rabbits received s.c. two polydimethylsiloxane implants (1.2 cm, filled length) containing crystalline estradiol-1713 as described previously [11,19,20]. Exposure of the rabbits to estrogen was manipulated in vivo by removal or reinsertion of the implants as indicated in each experiment.…”

Section: Methodsmentioning

confidence: 99%

“…Rabbits (n = 3 rabbits per group) were either exposed to estradiol continuously for 11, 12, or 13 days (estradiol maintained: 48 h, 72 h, 96 h, respectively), withdrawn from estradiol on Day 9 for 48 h or 72 h (estradiol withdrawn: 48 h, 72 h), or withdrawn on Day 9 for 48 h and then given replacement estradiol on Day 11 for an additional 48 h (estradiol replaced). From previous studies we knew that the corpora lutea remain responsive to estradiol within the first 48 h of estradiol deprivation [4,11,20]. Plasma progesterone concentration was measured on Days 9 (n = 18 rabbits), 11 (n = 12), 12 (n = 6), and 13 (n = 6) of pseudopregnancy to confirm the efficacy of estradiol implant manipulation.…”

Section: Experiments Imentioning

confidence: 99%

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Expression of the Steroidogenic Acute Regulatory Protein in the Corpus Luteum of the Rabbit: Dependence upon the Luteotropic Hormone, Estradiol-17β1 1

Townson

Wang

Keyes

et al. 1996

Biology of Reproduction

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The recent characterization of the mitochondrial protein, Steroidogenic Acute Regulatory (StAR) protein, as a rate-limiting protein in steroidogenesis prompted us to investigate whether StAR is expressed in the rabbit corpus luteum and whether the expression of StAR is responsive to estradiol-17 beta, the luteotropic hormone in the rabbit. In rabbits treated continuously with exogenous estradiol through Day 13 of pseudopregnancy (n = 9), immunoblot analysis revealed that luteal expression of StAR was stable, ranging from 8.5 to 9.7 U of corrected integrated optical density. Plasma progesterone concentration (mean +/- SEM) remained elevated in these rabbits (14.3 +/- 2.1 ng/ml). In contrast, expression of StAR decreased in corpora lutea of rabbits deprived of estradiol for the last 48 and 72 h of the experiment (4.9 +/- 2.2 and 0.3 +/- 0.2 U, respectively, n = 3 per group), and was associated with a decline in plasma progesterone (0.8 +/- 0.1 and 0.5 +/- 0.3 ng/ml, respectively). Replacement of estradiol after 48 h of estradiol deprivation (n = 3) stimulated the reappearance of StAR (10.3 +/- 2.6 U) and the restoration of plasma progesterone (10.4 +/- 4.9 ng/ml). [35S]Methionine labeling of proteins in rabbit corpora lutea revealed that several isoforms of StAR protein were specifically synthesized in response to estradiol treatment. Collectively, these observations are consistent with a proposed role for StAR in the mediation of the luteotropic effect of estrogen to promote the synthesis of progesterone in the rabbit.

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Section: Methodsmentioning

confidence: 99%

Section: Experiments Imentioning

confidence: 99%

Expression of the Steroidogenic Acute Regulatory Protein in the Corpus Luteum of the Rabbit: Dependence upon the Luteotropic Hormone, Estradiol-17β1 1

Townson

Wang

Keyes

et al. 1996

Biology of Reproduction

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“…After decapitation of the rats, trunk blood was collected into heparinized tubes and then centrifuged at 1740 g for 20 min. The plasma was frozen in liquid nitrogen, and stored at À20 8C until extracted and assayed for 20a-dihydroprogesterone according to the method previously described by Bender et al (27).…”

Section: Radioimmunoassaymentioning

confidence: 99%

Downregulation of long-form prolactin receptor mRNA during prolactin-induced luteal regression

Bowen

Telleria²,

Towns³

et al. 2000

European Journal of Endocrinology

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Objective: Prolactin is capable of both trophic and lytic actions in rat corpora lutea. In corpora lutea responding to a trophic prolactin signal, the long form of the prolactin receptor is the dominant form and is upregulated by prolactin. We investigated whether mRNA for the short form of the prolactin receptor was dominant in corpora lutea responding to a lytic prolactin signal, and whether the relative concentrations of the mRNAs for both forms of the prolactin receptor were changed during this response. Design and methods: Immature rats were ovulated by injection of 5 IU equine chorionic gonadotrophin and 5 IU human chorionic gonadotrophin, and were hypophysectomized shortly after ovulation. Nine days after hypophysectomy, rats were injected with prolactin (500 mg/day) or vehicle for 24 (n 6, n 6) or 72 h (n 13, n 5). Total RNA was isolated from corpora lutea and mRNA for both types of prolactin receptor were analyzed by semiquantitative RT-PCR using the ribosomal protein S16 as the internal control. Results: The intensities of the long-and short-form prolactin receptor signals were normalized to the S16 internal control and expressed as relative densitometric units. The normalized values at 24 h for prolactin-treated vs vehicle-treated rats were 0.23 6 0.05 vs 0.49 6 0.15 (P > 0.05) for the short form and 4.04 6 0.8 vs 4.23 6 0.6 (P > 0.05) for the long form. The values for 72 h were 0.30 6 0.05 vs 0.24 6 0.05 (P > 0.05) for the short form and 2.76 6 0.4 vs 5.53 6 0.3 (P < 0.01) for the long form respectively. Conclusion: The long form of the prolactin receptor is the dominant form at both time-points; however, the concentration of mRNA for this receptor isoform was speci®cally downregulated by prolactin treatment. Our results suggest that the short form of the prolactin receptor alone is unlikely to mediate the luteolytic action of prolactin, but that luteolytic events may be in¯uenced via a change in the ratio of the two receptor isoforms.

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“…On Day 1 of pseudopregnancy, all rabbits received two polydimethylsiloxane implants containing crystalline estradiol-17p, s.c. The dimensions of these implants and the procedure have been described previously [16,17,19]. Subsequently, luteal function was manipulated by the removal or the removal and replacement of the estradiol implants at the times indicated in each experiment.…”

Section: Animalsmentioning

confidence: 99%

“…With this approach, the timing of onset of regression is known precisely, enabling a rigorous temporal analysis of the potential involvement of macrophages in regression initiated in this manner. Further, since incipient regression can be reversed and progesterone synthesis can be restored by replacement of estradiol [17,18], the potential involvement of macrophages in these responses can also be evaluated.…”

Section: Introductionmentioning

confidence: 99%

Estrogen withdrawal Induces Macrophage Invasion in the Rabbit Corpus Luteum1

Naftalin

Bove

Keyes

et al. 1997

Biology of Reproduction

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Macrophages within the corpus luteum are associated with spontaneous luteal regression in a number of species. However, an understanding of the consequences of macrophage recruitment on the functional capacity and responsiveness of the luteal tissue has remained elusive. Here we investigate the temporal appearance of macrophages and their potential impact in corpora lutea of rabbits, in which a rapid fall in progesterone synthesis and premature regression of the corpus luteum are initiated by withdrawal of the luteotropic hormone estradiol-17beta. Removal of estradiol implants, placed subcutaneously, induced a significant increase in the average number of macrophages per high-power field (hpf) in corpora lutea (p < 0.05) within 72 h. Replacement of the estradiol implants 48 h after their removal resulted in a marginal rebound of plasma progesterone and a variable number of luteal macrophages (range: 6-160 macrophages/hpf) among the 11 rabbits. A third experiment revealed that the relative numbers of macrophages within the corpora lutea have no apparent relationship to rates of progesterone synthesis in vitro: progesterone production (ng/mg tissue) did not differ (p > 0.05) between corpora lutea of estradiol-maintained rabbits and those of estradiol-replaced rabbits despite obvious differences in numbers of luteal macrophages (2 +/- 1 vs. 42 +/- 10 macrophages/hpf, respectively; p < 0.05). We conclude that the entry/recruitment of macrophages into the rabbit corpus luteum is sensitive to the luteotropic hormone estradiol-17beta and that the presence of macrophages does not preclude the continuation of progesterone production in surviving luteal tissue revitalized after estradiol removal/replacement.

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Steroidogenic Effect of 170-Estradiol in the Rabbit: Stimulation of Progesterone Synthesis in Prematurely Regressing Corpora Lutea*

Cited by 45 publications

References 21 publications

Expression of the Steroidogenic Acute Regulatory Protein in the Corpus Luteum of the Rabbit: Dependence upon the Luteotropic Hormone, Estradiol-17β1 1

Expression of the Steroidogenic Acute Regulatory Protein in the Corpus Luteum of the Rabbit: Dependence upon the Luteotropic Hormone, Estradiol-17β1 1

Downregulation of long-form prolactin receptor mRNA during prolactin-induced luteal regression

Estrogen withdrawal Induces Macrophage Invasion in the Rabbit Corpus Luteum1

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