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PubMed2002

Asynchrony in the estrous cycles of golden hamsters (Mesocricetus auratus).

The golden hamster has been described as exhibiting estrous cycle synchrony caused by social dominance. This has recently been reexamined by J. C. Schank (2000, Horm. Behav. 38, 94-101) with the aid of computer simulations. He concluded that there is no evidence for cycle synchrony among golden hamsters. In the present article we confirm this theoretical approach with the help of long-term experiments. Indeed, estrous cycle asynchrony was observed. Singly housed female golden hamsters in phase with their neighbors and in physical contact desynchronized their 4-day cycles after 2 or 3 weeks. Asynchrony was caused mainly by stochastic 5-day cycles. Statistical analysis was performed using a Monte-Carlo bootstrap approach. Based on the empirical data, an individual-based computer model was developed to simulate the dynamics of cycle desynchronization. Potential advantages were deduced for the population level. It emerged that estrous cycle asynchrony led to higher reproductive success for females where the probability of fertilization was low (e.g., after hibernation, poor habitat).

Animals↗
PubMed1995

Temporal and spatial alterations in uterine estrogen receptor and progesterone receptor gene expression during the estrous cycle and early pregnancy in the ewe.

Mechanisms regulating responses of the ovine uterus to endocrine and paracrine signals during the estrous cycle and pregnancy are likely to require tissue- and cell-specific regulation of steroid hormone receptor gene expression. To determine effects of day and pregnancy status (cyclic or pregnant) on uterine estrogen receptor (ER) and progesterone receptor (PR) gene expression, ewes were hysterectomized either on Day 1 (Day 0 = estrus/mating), 6, 11, 13, or 15 of the estrous cycle (n = 3/day) or on Day 11, 13, 15, 17, or 25 of early pregnancy (n = 5/day). Steady state levels of ER and PR mRNA were determined in endometrial and myometrial tissues by slot-blot hybridization and ribonuclease protection assays, respectively, using homologous ovine ER and PR cRNA probes. Changes in spatial expression of ER and PR mRNA and protein in uterine tissue sections were determined by in situ hybridization and immunocytochemical analyses. In cyclic ewes, steady state levels of endometrial ER mRNA were highest on Day 1, declined between Days 1 and 6, and increased between Days 11 and 15. However in pregnant ewes, endometrial ER mRNA levels decreased between Days 11 and 15 and increased slightly between Days 15 and 25. In cyclic ewes, levels of myometrial ER mRNA were highest on Day 1, decreased to Day 6, and remained low thereafter. In cyclic ewes, endometrial PR mRNA levels were highest on Day 1, decreased between Days 1 and 11, and then increased between Days 13 and 15. In cyclic ewes, myometrial PR mRNA levels were highest on Day 1 and declined thereafter. Endometrial PR mRNA levels were not different between cyclic and pregnant ewes on Days 11, 13, and 15. In pregnant ewes, PR mRNA levels were low on Day 11, increased between Days 11 and 17, and decreased between Days 17 and 25. In pregnant ewes, myometrial PR mRNA levels were low and did not change between Days 11 and 25. In situ hybridization and immunocytochemical analyses revealed distinct tissue- and cell type-specific alterations in uterine ER and PR mRNA and protein expression during the estrous cycle and early pregnancy that generally paralleled overall changes in steady state levels of ER and PR mRNAs. In the endometrium, the most striking observation was that PR mRNA and protein expression disappeared from the luminal and shallow glandular epithelium between Days 6 and 13 of the estrous cycle, whereas ER mRNA and protein expression was low on Days 6 and 11 and increased between Days 11 and 15 in the luminal and shallow glandular epithelium. During early pregnancy, expression of ER and PR mRNAs, as well as ER and PR protein, was very low or absent in the luminal and shallow glandular epithelium between Days 13 and 25 of pregnancy. Moreover, ER and PR mRNA and protein were consistently present at low levels in the stroma and deep glandular epithelium in both cyclic (Days 11-15) and pregnant (Days 11-25) ewes. Collectively, results suggest that uterine ER and PR gene expression is regulated in a tissue- and cell type-specific manner during the estrous cycle and early pregnancy.

Animals↗
PubMed1991

Dynamics of ovarian follicular development in cattle during the estrous cycle, early pregnancy and in response to PMSG.

Ovarian follicular dynamics of cattle were examined during the estrous cycle, early pregnancy and in response to PMSG. Number and size of follicles were monitored by ultrasonographic examinations. During the estrous cycle, distinct periods of follicular dominance (measured by the increase in difference in size between the largest and second largest follicle) occurred in both the luteal (Days 6-8) and proestrus (18-22) phases of the estrous cycle (two follicular waves). Associated with the well timed development of the first dominant follicle was a change in distribution of follicle numbers in small (less than 5 mm; increased on Days 2-4), medium (6-8 mm; increased on Days 3-5) and large (greater than or equal to 9 mm; increased on Days 6-9) follicular size classes. Follicular development was greater on the ovary bearing the CL for the period that the CL was present. The dominant follicle formed during the first follicular wave was capable of ovulating (6 of 8 heifers) following an injection of a synthetic analogue of prostaglandin F-2 alpha on Day 9 of the estrous cycle. During early pregnancy (Days 6-34), follicular development (size of largest follicle, number of follicles and total accumulated size of all follicles) on the ovary bearing the CL was suppressed between Days 24 and 34 of pregnancy. This was a local effect in that follicular development was sustained on the contralateral ovary. Therefore, the CL or conceptus may be regulating follicular development in a manner to help prevent luteolysis. Associated with the injection of PMSG was an initial increase in the number of small follicles followed by their recruitment into medium and large size classes leading to ovulation. Number of follicles greater than 5 mm on the Day of estrus was related (r = .97) to the number of subsequent embryos and oocytes collected. Ultrasonography is a valuable technique to monitor ovarian follicular dynamics in cattle, and can thereby be used to infer changes in physiological and endocrine states.

Animals↗
PubMed1988

Factors associated with shortened estrous cycles after abortion in beef heifers.

Forty-six crossbred Hereford heifers were allotted into five experimental groups. Fenprotalene, a prostaglandin analogue, was administered to induce abortion and (or) to regress the corpus luteum (CL) in four groups of heifers about 75 d after conception. The four groups were 1) pregnant heifers, 2) pregnant heifers with the ovary contralateral to the gravid uterine horn removed 24 h after fenprostalene injection, 3) same as Group 2 but with the ipsilateral, rather than the contralateral, ovary removed and 4) heifers with uterus removed (ovaries intact) about 35 d after conception. A fifth group of nonpregnant heifers received implants containing norgestomet from 10 to 76 d after estrus and were given fenprostalene 24 h before removal of the implant. Average length of the first estrous cycle after the fenprostalene injection was 11.2, 8.3, 9.7 and 19.1 for Groups 1, 2, 3 and 5, respectively. Estrous cycles were longer (P less than .05) in norgestomet-treated heifers. Hysterectomized heifers (Group 4) did not exhibit a second estrus by 50 d after fenprostalene treatment; otherwise, all first estrous cycles after the fenprostalene injection were either "short" (7 to 13 d) or "normal" (17 to 23 d). Twenty-two of 24 heifers that aborted had short estrous cycles and two had normal estrous cycles. Short estrous cycles occurred after abortion regardless of whether the ovary ipsilateral or contralateral to the previously gravid uterine horn ovulated. Early regression of the CL (short luteal phase) did not occur in nonpregnant heifers after long-term progestogen stimulation or after hysterectomy, but it did occur in heifers with a previously gravid uterus.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortifacient Agents↗
PubMed1996

Glutathione-S-transferase in rat ovary: its changes during estrous cycle and increase in its activity by estradiol-17 beta.

Glutathione-S-transferases (GSTs) are drug metabolizing and detoxification enzymes, involved in the intracellular transport and metabolism of steroid hormones. This study indicated that the enzyme was heterogeneously distributed and changed during estrous cycle. The enzyme was found to be predominantly located in the cytosolic fraction while considerable activity was also observed in the mitochondrial and microsomal fractions. The activity of GST was measured during different stages of estrous cycle, viz proestrous, estrous, metestrous and diestrous. The change in its activity was observed during different stages of estrous cycle. Estrous stage was observed to have the highest GST activity. Immature (28-29 days old) rats treated with estradiol-17 beta (5 micrograms in 0.2 ml oil/animal/day, and 10 micrograms in 0.2 ml oil/animal/day, for 3 days), ovarian GST activity seemed to increase significantly (P < 0.01). This increase in the activity and the heterogeneous distribution of GST indicates the functional role of this enzyme in the ovary under endocrine regulation.

Animals↗
PubMed2001

Insulin gene expression pattern in rat pancreas during the estrous cycle.

Sex steroid hormones influence insulin homeostasis and glucose metabolism, estradiol (E2) and progesterone (P4) induce changes in both fasting and postprandial insulinemia in rodents, however, insulin gene expression during estrous cycle is unknown. The aim of the present study was to determine an insulin gene expression pattern during the estrous cycle in the rat. Groups of 6 adult rats in each day of the estrous cycle were used. Serum P4, E2, testosterone (T) and insulin concentrations were determined by radioimmunoassay (RIA). A Northern blot analysis was performed to assess insulin gene expression in pancreatic tissue. We found a marked variation in insulin gene expression during the estrous cycle. The highest insulin expression was observed during the proestrus day. Interestingly, E2 and P4 but not T levels were correlated with changes in insulin mRNA content. The variations in serum insulin during the cycle were correlated with its mRNA content in pancreas. The overall results showed variations in serum insulin and insulin gene expression during estrous cycle of the rat that correlated with circulating E2 and P4 levels.

Animals↗
PubMed1996

Effects of the estrous cycle and ovarian hormones on behavioral indices of anxiety in female rats.

The influence of the estrous cycle and the effects of exogenous administration of estradiol and progesterone on level of anxiety were studied in intact and ovariectomized rats. Intact Sprague-Dawley female rats were classified according to the stages of estrous cycle. Another group of rats was ovariectomized bilaterally and, 14 days after surgery, they received estradiol benzoate (10 micrograms/kg, s.c.) and/or progesterone (25 mg/kg, s.c.) or corn oil (1 ml/kg). The behavioral tests began 3 h after estradiol or 6 h after progesterone and consisted of: (1) exploration of an elevated plus-maze; and (2) retention of a passive avoidance response. Open-arm exploration of the plus-maze varied according to light intensity and the stages of the estrous cycle. There was a slight increase in open-arm exploration by rats in metestrus, under high light intensity. Low light intensity increased the exploration of the open arms by rats in proestrus and estrus, compared to the other phases of the cycle. Retention of the passive avoidance response was inhibited during proestrus and estrus. Progesterone increased open-arm exploration of the plus-maze under high light conditions, whereas estradiol antagonized this effect. Retention of passive avoidance was inhibited after estradiol or progesterone injection. These results suggest that the behavioral indices of anxiety can vary across the estrous cycle, that low light intensities have anxiolytic-like effects, and that the sensitivity to this effect is higher during proestrus and estrus. This could be explained through modulatory effects of ovarian hormones upon behavioral indices of anxiety.

Animals↗
PubMed1988

Plasma gonadotropin and progesterone concentrations during the estrous cycle of Finn, Suffolk and Targhee ewes.

Hormonal profiles during the estrous cycle of Finn, Suffolk and Targhee ewes were compared in six ewes of each breed. Blood samples were drawn by venipuncture at 8-h intervals from onset to onset of consecutive estrous periods. Number of corpora lutea (CL) and ovarian follicles >/=3 mm in diameter on Day 10 (estrus = Day 0) were observed using endoscopy. Estrous cycle length was 14.9, 15.6 and 16.4 d (P<0.01) in Finn, Suffolk and Targhee ewes, respectively. Finns had more (P<0.001) CL (3.5) than Suffolks (2.0) and Targhees (1.8), but luteal phase progesterone concentrations were similar among breeds in peak level and area under the curve. In Finn ewes, the amplitude of the preovulatory LH surge was lower (P<0.01) and tended to occur later in estrus; otherwise LH levels and patterns were similar among breeds. A coincident follicle stimulating hormone (FSH) preovulatory surge occurred in most ewes, the amplitude of which was related to that of luteinizing hormone (LH); r = 0.67, P<0.01. Plasma FSH levels and patterns were similar in Finn, Suffolk and Targhee ewes and most ewes had three to four secretory episodes. Follicles >/=3 mm averaged 1.8, 1.0 and 1.2 (P>0.1) in Finn, Suffolk and Targhee ewes, respectively. Results indicate that the higher ovulation rate of the Finn ewe is not elicited by increased FSH levels at any stage of the estrous cycle.

Journal Article↗
PubMed1996

Substance P and neurokinin A variations throughout the rat estrous cycle; comparison with ovariectomized and male rats: II. Trigeminal nucleus and cervical spinal cord.

Substance P and neurokinin A were assayed in the trigeminal nucleus and cervical spinal cord of 4-day cycling female, ovariectomized, and male rats. During the estrous cycle, levels were largely stable in the trigeminal nucleus. In ovariectomized rats, the levels differed from those on any day of the estrous cycle suggesting a weak effect of ovarian steroids. In males, the variations in the substance P and neurokinin A contents in the trigeminal nucleus were not similar to those in either cyclic or ovariectomized rats. The levels fluctuated substantially in the cervical spinal cord. During the first 3 days of the estrous cycle, the substance P and neurokinin A contents fell concomitant with the 17 beta-estradiol surge, suggesting a downregulation of substance P and neurokinin A contents by 17 beta-estradiol. Furthermore, on estrus, progesterone seemed to inhibit the accumulation of both neurokinins. Testosterone may stimulate accumulation of substance P and neurokinin A in the cervical spinal cord, with a marked circadian rhythm. These results are in favor of the neurokinin content of the spinal cord being regulated by the gonadal steroids. In the trigeminal nucleus, only testosterone has an effect.

Animals↗
PubMed1996

Quantitative changes in macrophage distribution in normal mouse ovary over the course of the estrous cycle examined with an image analysis system.

PROBLEM: The current study considered the distribution of macrophages within the major ovarian structures throughout the estrous cycle. METHODS: Immunohistochemical analyses were carried out using an avidin-biotin-peroxidase staining method and the rat anti-mouse macrophage monoclonal antibody anti-Mac-l was applied to stain macrophages. A computer-assisted image analysis system was used to quantify and compare the distribution of macrophages within individual ovarian structures during the estrous cycle. The following morphological structures were analyzed: primordial, preantral, antral, pre-Graafian, and atretic follicles; first-, second-, and third-generation corpora lutea; and the interstitium. The analysis included follicular and corpus luteum substructures: theca, granulosa cells, and interstitium. The system allows the estimation of macrophage distribution as a macrophage density per microns2 of the defined area. RESULTS: Primordial and preantral follicles did not contain macrophages during all stages of the estrous cycle. In antral, pre-graafian, and graafian follicles, macrophages were located and quantified only in the theca and were not detected in the granulosa cell layer. In contrast, atretic follicles showed macrophage localization in both thecal and granulosa cell layers. Macrophages were present in small numbers in the granulosa luteal cell layer and in high numbers in the thecal layer of newly developing corpora lutea. In the second generation of corpus luteum, macrophages followed the same pattern of distribution, while old corpora lutea contained significantly higher numbers of macrophages in both thecal and luteal cell layers. Surprisingly, significant quantitative changes in the macrophages distribution were detected over the course of the estrous cycle. Macrophage density was significantly higher in proestrus and metestrus when compared with the density in diestrus and estrus in most of the studied substructures with the exception of atretic follicles. Atretic follicles showed high macrophage density throughout the cycle with a two-fold higher density at metestrus. CONCLUSION: Macrophages were present in the mouse ovary over the course of the estrous cycle. The greatest numbers of macrophages appearing in corpora lutea and in atretic follicles suggest a role for macrophages in corpus luteum differentiation and follicular atresia. Their patterns of distribution at proestrus and metestrus within microenvironmental compartments suggests a functional correlation with the events of ovarian development.

Animals↗
PubMed2000

Tumor necrosis factor-alpha and its receptor in bovine corpus luteum throughout the estrous cycle.

The objective of this study was to investigate tumor necrosis factor alpha (TNF-alpha) expression, the presence of functional TNF-alpha receptors, and expression of TNF receptor type I (TNF-RI) mRNA in the bovine corpus luteum (CL) during different stages of the estrous cycle. Reverse transcription (RT)-polymerase chain reaction (PCR) showed no difference in TNF-alpha mRNA expression during the estrous cycle. Concentrations of TNF-alpha in the CL tissue increased significantly from the mid to the late luteal stage and decreased thereafter (P < 0.05). An RT-PCR analysis showed higher levels of TNF-RI mRNA in CL of Days 3-7 than of other stages (P < 0.05). (125)I-TNF-alpha binding to the membranes of bovine CL was maximal after incubation at 38 degrees C for 48 h. The binding was much greater for TNF-alpha than for related peptides. A Scatchard analysis revealed the presence of a high-affinity binding site in the CL membranes collected at each phase of the estrous cycle (dissociation constant: 3.60 +/- 0.58-5.79 +/- 0.19 nM). In contrast to TNF-RI mRNA expression, the levels of receptor protein were similar at each stage of the estrous cycle. When cultured cells of all luteal stages were exposed to TNF-alpha (1-100 ng/ml), TNF-alpha stimulated prostaglandin F(2alpha) and prostaglandin E(2) secretion by the cells in a dose-dependent fashion (P < 0.01), especially during the early luteal phase, although it did not affect progesterone secretion. These results indicate the local production of TNF-alpha and the presence of functional TNF-RI in bovine CL throughout the estrous cycle, and suggest that TNF-alpha plays some roles in regulating bovine CL function throughout the estrous cycle.

Animals↗
PubMed1997

Regulation of the natriuretic peptide system in rat uterus during the estrous cycle.

Uterine natriuretic peptides may be involved in the alterations that occur in the uterus during the estrous cycle through its role in hydromineral balance. The following studies were performed to determine whether uterine natriuretic peptides and receptors follow a cyclic pattern during the estrous cycle. The results obtained show that atrial natriuretic peptide (ANP) content in rat uterine tissue was low in proestrus (8.5 +/- 2.6 pg/g) and significantly increased (P < 0.001) in estrus (71.5 +/- 16.6 pg/g), metestrus (82.6 +/- 19.7 pg/g) and diestrus (91.0 +/- 19.4 pg/g), whereas plasma ANP was not altered during the cycle. Similarly, measurement of uterine ANP mRNA by reverse transcribed polymerase chain reaction (RT-PCR) indicated lowest levels of ANP mRNA at proestrus. Measurement of C-type natriuretic peptide (CNP) by a specific and sensitive radioimmunoassay revealed that uterine CNP also varies with the estrous cycle. Uterine CNP was low in diestrus (143.2 +/- 22.4 pg/mg protein) as compared with proestrus, estrus and metestrus (305.3 +/- 51.5, 267.5 +/- 44.9, 291 +/- 41.2 pg/mg protein respectively, P < 0.05). Autoradiography performed on uterine tissue slices localized natriuretic peptide receptors to myometrial smooth muscle layers and to endometrial uterine glands. High binding of 125I-ANP was observed in proestrus and estrus with 60-75% decreases during metestrus and diestrus. Binding of 125I-tyr0CNP to uterine slices was also high during proestrus, but declined by 35% at estrus, metestrus and diestrus. The alterations in the receptors were also observed at the level of synthesis. RT-PCR detection of guanylyl cyclase A (GC-A) receptor mRNA and guanylyl cyclase B (GC-B) mRNA showed high signals at proestrus but 4- and 2-fold reductions respectively at metestrus and diestrus. In conclusion, variations in uterine ANP and CNP and their receptors during the rat estrous cycle imply the involvement of the natriuretic peptides in uterine hydromineral balance and myometrial motor activity.

Animals↗
PubMed2001

Presence of the acute phase protein, bikunin, in the endometrium of gilts during estrous cycle and early pregnancy.

Noninvasive, epitheliochorial placental attachment in the pig is regulated through endometrial production of protease inhibitors. The objective of the present study was to determine if the light-chain serine protease inhibitor of the inter-alpha-trypsin inhibitor family, bikunin, is produced by the porcine endometrium during the estrous cycle and early pregnancy. Western blot analysis revealed the presence of bikunin in uterine flushings of gilts collected during the luteal phase of the estrous cycle and early pregnancy (Days 12-18). However, bikunin unbound to the inter-alpha-trypsin heavy chains was detected only in endometrial explant culture medium obtained from estrus and pregnant (Days 12, 15, and 18) gilts. Endometrial bikunin gene expression was lowest on Day 10 of the estrous cycle and pregnancy, followed by a 30- to 77-fold increase on Day 15 of the estrous cycle and pregnancy. Bikunin gene expression decreased on Day 18 of the estrous cycle, whereas endometrial bikunin gene expression continued to increase in pregnant gilts. Bikunin mRNA was localized to the uterine glands between Days 15 and 18 of the estrous cycle and pregnancy. In addition to its role as a protease inhibitor, bikunin functions in stabilization of the extracellular matrix, which suggests that bikunin could be involved with facilitating placental attachment to the uterine epithelial surface in the pig.

Animals↗
PubMed1993

Estrous cycle characteristics of postpubertal gilts approaching anestrus due to limited dietary energy intake.

Twenty-nine Duroc x (Yorkshire x Landrace) gilts, approximately 9 mo of age and each having experienced at least three estrous cycles, were allotted randomly to five dietary treatments. Each treatment provided a different daily intake of metabolizable energy: .25, .5, .75, 1.0 Mcal (severely restrictive [RES]; chosen to cause cessation of estrous cycles) or 3.4 Mcal (control; designed for maintenance of estrous cyclicity). Blood samples were drawn by venipuncture every 3 d and sera were assayed for progesterone (P4) concentration. Estrous cycle length was estimated by defining d 0 as the last day when serum P4 concentrations were < 1 ng/mL before increasing to > 1 ng/mL. Gilts were considered acyclic when serum P4 levels remained < 1 ng/mL for four consecutive samples (9 d). Anestrus occurred after 78.7 +/- 6.1 d in all RES gilts (n = 23) and in one control on d 24. Compared with the control treatment, RES treatments resulted in longer (P < .05) average estrous cycles (21.0 +/- .2 vs 20.2 +/- .3 d) and greater (P < .05) mean serum P4 concentrations (13.7 +/- .4 vs 11.4 +/- .8 ng/mL). There were no differences in P4 or cycle length measurements among RES treatments. Cycle duration and serum P4 concentrations of the final estrous cycle before anestrus were similar to those of previous cycles. It is concluded that severe energy restriction caused elevated serum P4 concentrations. Neither cycle length nor serum P4 concentration was notably altered as gilts neared anestrus.

Animal Nutritional Physiological Phenomena↗
PubMed1989

Distinct pulsatile prolactin secretory patterns during the estrous cycle: possible encoding for diverse physiological responses.

PRL levels during the estrous cycle have been reported to be low, with the notable exception of the afternoon proestrous surge. The present study was designed to evaluate the pulsatile pattern of PRL secretion during the low secretory phases of the cycle. Animals were bled at 3-min intervals for 150 min during proestrus morning (AM), estrus AM and evening (PM), metestrus AM, and diestrus AM and PM. Using the algorithm Detect, pulse frequency, duration, interval, peak and trough values, area under the pulses, and mean PRL levels were calculated. PRL secretion was pulsatile during all stages of the estrous cycle, although the pattern varied considerably among the different cycle stages. Pulse frequency was highest during estrus and lowest during diestrus. All quantitative pulse parameters (peak, trough, amplitude, and area under pulse) were also higher during estrus and lowest in diestrus. Analysis of area under the pulse using frequency distribution indicated that at least two subpopulations of pulses, i.e. small mass and large mass pulses, were observed in certain stages of the cycle. Small mass pulses were present at all stages of the cycle; while their frequency remained unchanged, changes in other parameters were observed at different stages which did not always correlate with changes in mean PRL levels. Big mass pulses, on the other hand, presented a clear change in pulse frequency with values rising progressively from diestrus PM through proestrus to peak at estrus. Between estrus PM and metestrus AM these big mass PRL pulses essentially disappeared. In contrast to the marked changes in frequency, big mass PRL pulses were remarkably homogeneous in other quantitative characteristics. The results indicate that distinct changes in PRL pulsatility patterns occur during the estrous cycle; these changes are related to both the pattern and the quality of PRL pulses. Based on the observations of a companion study (28) and other data, we suggest that the genesis of the big mass and small mass PRL pulses involves dopaminergic and nondopaminergic mechanisms, respectively. The timing and selectivity of the changes in PRL pulsatile patterns suggest that those patterns may encode different signals for expression of the diverse actions of PRL on reproductive tissues.

Animals↗
PubMed2002

Dynamics of messenger RNAs encoding inhibin/activin subunits and follistatin in the ovary during the rat estrous cycle.

Quantitative changes in ovarian inhibin/activin subunit and follistatin mRNAs during the rat estrous cycle were examined by ribonuclease protection assay using digoxygenin-labeled RNA probes. Levels of ovarian inhibin alpha subunit mRNA remained low throughout estrus, metestrus, and diestrus; abruptly increased on the morning of proestrus; then rapidly decreased when the primary gonadotropin surge occurred. A similar changing pattern was observed in inhibin/activin beta(A) subunit mRNA. On the other hand, inhibin/activin beta(B) subunit mRNA showed a different changing pattern. Levels of beta(B) subunit mRNA remained constant during metestrus and diestrus, abruptly decreased on the afternoon of proestrus, then quickly recovered from the nadir by 1100 h on estrus. Throughout the rat estrous cycle, especially during the periovulatory period, alpha subunit mRNA levels were considerably higher than beta(A) and beta(B) subunit mRNA levels. In addition, changes in plasma concentrations of inhibin A and inhibin B were very similar to that in ovarian beta(A) and beta(B) subunit mRNA levels, respectively, with several-hour delays. These results suggest that levels of beta subunit mRNAs restrict secretion of dimeric inhibins. Levels of follistatin mRNA remained low from the midnight of metestrus to the midnight of diestrus, then increased until initiation of the primary gonadotropin surge. Thereafter, follistatin mRNA decreased, reached the nadir at 0200 h on estrus, then increased abruptly at 1100 h on estrus. Afterward, follistatin mRNA levels remained high until the morning of metestrus. The changing pattern of ovarian follistatin mRNA was similar to, and preceded, the changes in plasma concentrations of progesterone, suggesting that ovarian follistatin may modulate progesterone secretion during the rat estrous cycle.

Activins↗
PubMed1990

Electrophoretic characterization of proteins in oviduct fluid of cows during the estrous cycle.

This study was undertaken to examine the in vivo protein composition of the bovine oviduct during the estrous cycle. Oviduct fluid was collected daily from four oviduct-cannulated dairy cows for a total of four complete estrous cycles. Fluid secretion followed a definite cyclic pattern, with maximum secretion occurring at estrus in all cycles. Protein concentration fluctuated during the cycle and varied among animals. In general, protein concentration was lower at the time of estrus. Total protein in oviduct fluid, however, was higher around estrus, indicating increased transudation or secretion by the oviduct. One-dimensional SDS-PAGE separation revealed the protein pattern of oviduct fluid to be generally similar to that of blood serum and follicular fluid. Two proteins appeared to be oviduct-specific. The first, a protein of approximately 47 kDa, was evident in oviduct fluid throughout the estrous cycle. The second protein, evident as a broad diffuse staining band above albumin, appeared for only 3-4 days at or near ovulation. This protein had a molecular weight of 80-95 kDa and stained positive for carbohydrate with periodic acid-Schiff reagent. These studies indicate that the in vivo protein composition of oviduct fluid varies with the estrous cycle, and that around estrus, an oviduct-specific glycoprotein is present.

Animals↗
PubMed1998

Luteal expression of steroidogenic factor-1 mRNA during the estrous cycle and in response to luteotropic and luteolytic stimuli in ewes.

Steroidogenic factor-1 (SF-1) is a transcription factor involved in regulating basal and/or cAMP-induced increases in expression of several components of the steroidogenic pathway, including cytochrome P450 side-chain cleavage (P450scc), steroidogenic acute regulatory protein (StAR), and 3beta-hydroxysteroid dehydrogenase/delta5, delta4 isomerase (3beta-HSD). In experiment 1, on days 3, 6, 9, 12, and 15 of the estrous cycle, steady-state concentrations (fmol/microg poly A+ RNA) of SF-1 mRNA in luteal tissue were 0.09 +/- 0.01, 0.17 +/- 0.01, 0.24 +/- 0.03, 0.30 +/- 0.09, and 0.20 +/- 0.05, respectively (estrus = day 0; n = 4/d). Concentrations of SF-1 mRNA increased (p < 0.05) between days 3 and 12, but were not different among the other days of the estrous cycle. Luteal concentrations of SF-1 mRNA and concentrations of progesterone in sera were highly correlated (p < 0.01; r = 0.72). In experiment 2, ewes on days 11 or 12 of the estrous cycle were injected with 25 mg prostaglandin F2alpha (PGF2alpha) into the jugular vein followed by an injection of 10 mg PGF2alpha i.m. 2 h later. Corpora lutea were collected 4, 12, and 24 h after the first injection of PGF2alpha (n = 4-5 ewes/time). Control luteal tissue was collected from ewes on days 11-13 of the estrous cycle, which had not been injected (n = 4) or had been injected with saline 24 h previously (n = 4). Steady-state concentrations of SF-1 mRNA had decreased (p < 0.05) to 48% of control values by 4 h after injection, and remained low at 12 and 24 h. In experiment 3, ewes on days 9-12 of the estrous cycle were administered PGF2alpha (1 micromol), phorbol 12-myristate 13-acetate (PMA; 2 micromol), luteinizing hormone (LH; 20 microg), forskolin (50 microg), or vehicle (1 mL saline) directly into the ovarian artery. Corpora lutea were collected 0 (noninfused) 4, 12, or 24 h later (n = 3-4 animals/treatment/time) for quantification of SF-1 mRNA. Steady-state concentrations of mRNA encoding SF-1 were not affected by infusion of PGF2alpha or PMA, although concentrations of mRNA encoding StAR and 3beta-HSD were decreased (p < 0.05) by these treatments. Concentrations of mRNA encoding SF-1 were increased (p < 0.05) to 157 and 149% of control values by LH and forskolin, respectively, 12 h following infusion and returned to control values by 24 h following either treatment. In contrast, infusion of LH or forskolin did not change concentrations of mRNA encoding StAR, P450scc, or 3beta-HSD. In summary, during the estrous cycle, the pattern of expression of SF-1 mRNA was similar to the pattern of concentrations of progesterone in serum and expression of mRNA encoding P450scc, but differed from that previously shown for 3beta-HSD and StAR mRNA. The effects of administration of PGF2alpha on concentrations of SF-1 mRNA appeared to be dose-dependent. However, acute effects of PGF2alpha on mRNA encoding 3beta-HSD and StAR were observed when concentrations of mRNA encoding SF-1 were not influenced. In addition, although LH or forskolin increased luteal SF-1 mRNA 12 h following infusion, no increases in mRNA encoding StAR, P450scc, or 3beta-HSD were observed. Thus, during the midluteal phase of the estrous cycle, neither luteotropic nor luteolytic hormones appear to coordinately regulate mRNA encoding SF-1 and mRNA encoding StAR, P450scc, or 3beta-HSD.

3-Hydroxysteroid Dehydrogenases↗