| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Ovary |
Reproductive Medicine Unit, Department of Obstetrics and Gynaecology, The University of Adelaide, The Queen Elizabeth Hospital, Woodville, South Australia, 5011, Australia
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
corpus luteum function, immunology, pregnancy, progesterone, seminal vesicles
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Mating appears to provide a stimulus for recruitment of additional macrophages into the follicle/corpus luteum, because on the day after ovulation, mice exhibited more macrophages in corpora lutea of pregnant mice compared to unmated mice [8]. The mechanism behind this finding may involve the prolactin surge associated with cervical stimulation during copulation, as has been shown for the increase in proliferative activity of vascular cells of the corpus luteum of pregnancy [10]. Alternatively, a component of semen may be responsible. Indeed, exposure to seminal plasma at mating induces an inflammatory response within the uterus of mice, resulting in local production of cytokines and recruitment of leukocytes into the endometrium [11]. That seminal plasma exposure of the uterus can influence the ovary has been demonstrated in estrous pigs in which a reduction in the interval between the LH surge and ovulation occurred for the ovary adjacent to the uterine horn receiving infusion of seminal plasma [12]. It has also been shown that seminal plasma exposure of uterine horns in pigs increases the concentration of plasma progesterone [13].
The aims of this study were to determine whether exposure to seminal plasma during mating in mice was able to alter ovarian function. We hypothesized that the leukocyte response induced within the uterus in response to seminal plasma exposure would extend to the ovary and, in particular, enhance macrophage recruitment into periovulatory follicles with a resulting increase in progesterone levels during the early stages of luteinization. Progesterone secreted by the corpus luteum is vital for the establishment of early pregnancy due to progestational effects on the uterus, and studies have shown that experimental manipulation of progesterone levels in the early stages of pregnancy affects embryonic survival [14, 15]. The experimental approach used in the current study was to mate female mice with intact males (in which semen contains both sperm and seminal plasma), vasectomized males (in which semen contains seminal plasma only), or seminal vesicle-excised males (in which semen does not contain seminal plasma), and then assess ovaries for macrophage localization in corpora lutea and measure progesterone levels in blood.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
SV129 mice were obtained from the University of Adelaide, Australia, and were used between 8–13 wk of age. Mice were housed at The Queen Elizabeth Hospital, Adelaide, Australia, in a controlled environment of 24°C with a 14L:10D cycle. Water and food were available ad libitum. All experiments were approved by the University of Adelaide and The Queen Elizabeth Hospital animal ethics committees, and were performed in accordance with the National Health and Medical Research Council Australian Code of Practice for the Care and Use of Animals for Scientific Purposes.
Vasectomy
Male mice were anesthetized using halothane (Fluothane, Zeneca Ltd., Macclesfield, U.K.), and vasectomy was performed as previously described [16] with a minor modification. Briefly, a 1-cm vertical incision was made in the lower abdomen, and size 4.0 black braided silk sutures (Ethicon, Somerville, NJ) were used to ligate each vas deferens in two locations, spaced approximately 5 mm apart. The vas deferens was then cut between the two ligations and returned to the abdominal cavity. The peritoneum and skin layers were sutured and the mice were placed under a heat lamp until they regained consciousness. The mice were allowed to recover for 2–3 wk before mating commenced.
Seminal Vesicle Removal
This procedure was carried out as previously described [17]. Mice were anesthetized as they were for vasectomy, and a vertical incision was created in the lower abdomen. Each seminal vesicle was pulled out of the abdominal cavity taking care not to cause inadvertent rupture. The seminal vesicle was then quickly separated by blunt dissection from the coagulating gland, which was left intact and replaced into the abdominal cavity. The incision was sutured, and mice were allowed to recover as they were after vasectomy.
Matings and Estrous Cycle Tracking
One or two female mice were caged with individual males, and females were checked each morning for the presence of a vaginal plug to indicate that mating had occurred. Because matings with seminal vesicle-excised males do not produce a copulation plug, mating of these females was determined by the presence of sperm in a vaginal smear. Day 1 was designated as the day during which either a vaginal plug or a smear containing sperm was observed. Vaginal smears were performed using 30 µl of saline, which was wet-mounted onto a microscope slide for examination using an inverted Olympus CK2 microscope (Olympus, Tokyo, Japan). To obtain female mice that were unmated but at equivalent stages of the estrous cycle as mated mice (metestrus-1 for Day 1 of mating, metestrus-2 for Day 2, and diestrus for Day 4), daily vaginal smears were performed, and the relative proportions of epithelial cells, cornified epithelial cells, and leukocytes was assessed and used to determine the estrous cycle stage [18]. Female mice for estrous cycle tracking were housed in groups of three in a large cage. A male mouse housed within a smaller cage was placed inside the female cage to provide visual and olfactory stimuli to help maintain regular estrous cycles in the females.
Tissue and Blood Collection
Female mice were anesthetized with 2% Avertin (15 µl/g body weight injected i.p.) between 1100 h and 1400 h on either Day 1, 2, 4, 6, or 9 after mating, and blood was collected via cardiac puncture using a 23-gauge needle. Blood was allowed to clot at room temperature for up to 2 h, and serum was collected by centrifugation and stored at –20°C. Mice were killed via cervical dislocation and ovaries were immediately removed and placed into Hepes-buffered tissue culture medium-199 (TCM-199; ICN Biochemicals Inc., Costa Mesa, CA) containing 2 mM sodium bicarbonate, 2 mM sodium pyruvate, 25 mM Hepes, 100 IU/ml penicillin G, and 100 µg/ml streptomycin sulfate. Fat was removed from each ovary under a dissecting microscope (Wild M3Z; Heerbrugg, Switzerland) and the ovaries were either embedded in Jung tissue-freezing medium (Leica Instruments GmbH, Nussloch, Germany), frozen in liquid nitrogen-cooled isopentane, and stored at –80°C, or they were used for isolation of corpora lutea.
Corpora Lutea Culture
Incubation of corpora lutea was carried out according to methods previously described for rats [19, 20]. Corpora lutea were excised from ovaries and cleaned of excess stromal tissue under a dissecting microscope. Corpora lutea from both ovaries of a single mouse were pooled, and four were selected for preculture in bicarbonate-buffered TCM-199 containing 25 mM sodium bicarbonate, 0.23 mM sodium pyruvate, 27 µM phenol red, 100 IU/ml penicillin G, and 100 µg/ml streptomycin sulfate at 37°C for 30 min in 5% CO2 in air. Corpora lutea were then placed into 0.5 ml of bicarbonate-buffered TCM-199 in a stoppered glass vacutainer (two per tube) either with or without the addition of LH (bovine, AFP5500; kindly supplied by the National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD) at a final concentration of 1 µg/ml. Tubes were gassed with 5% CO2/95% O2 and cultured at 37°C for 2 h with gentle shaking. At the end of the incubation period, 100 µl of media was removed and stored at –20°C for later analysis.
Quantification of Ovulated Ova, Embryos, and Corpora Lutea
Oviducts collected from mice on Day 1 or 2 of mating (or metestrus for unmated mice) and flushed with Hepes-buffered TCM-199 to recover ova/embryos, which were counted and, for the Day 2 time point, were assessed for evidence of cell cleavage. Ovaries collected from mice on Day 4 were separated from excess fat and the number of corpora lutea were counted under a dissecting microscope. On Days 6 and 9 after mating, embryos were counted as implantation sites on uterine horns.
Progesterone Assay
The concentration of progesterone in serum and media was assayed using an RIA kit (Diagnostic Systems Laboratories, Webster, TX). The assay was performed following the manufacturer's instructions with the exception that the volume of reagents was halved. Values were obtained from a 1–150 nM standard curve. The intraassay coefficient of variation was 8.2% (83.5 nM) and the interassay coefficient of variation was 12.4% (76.2 nM).
Immunohistochemistry
Fresh, frozen sections of ovaries were cut at 6 µm using a cryostat (Leica CM 1850; Leica Instruments). Approximately 5–6 regions of each ovary were sectioned at 100-µm intervals, and sections were stored in desiccated boxes at –80°C. Slides were thawed to room temperature and then fixed in 96% ethanol for 10 min at 4°C. Sections were incubated with monoclonal antibodies F4/80 (which recognize a cell surface glycoprotein of monocytes and macrophages [21]) or TIB120 (which recognize major histocompatibility complex [MHC] class II [Ia] on activated macrophages and dendritic cells; American Type Culture Collection, Manassas, VA) overnight at 4°C in a humidified container. Antibodies were used as an undiluted hybridoma supernatant with 10% normal mouse serum. Slides were washed in PBS three times for 5 min, followed by a blocking step in PBS with 1% BSA, and then incubated with biotinylated rabbit anti-rat immunoglobulin G (1:300 dilution in PBS with 10% normal mouse serum and 1% BSA; DAKO, Carpinteria, CA) at 4°C for 2 h in a humidified container. Slides were then washed in PBS and PBS/BSA, and incubated with avidin conjugated to horseradish peroxidase (1:400 dilution in PBS with 10% normal mouse serum and 1% BSA; DAKO) at 4°C for 40 min. After another round of washing in PBS, bound antibody was visualized by incubating sections with 3,3'-diaminobenzidine (DAB) in Tris buffer containing urea hydrogen peroxide (Sigma Aldrich Chemical Company, St. Louis, MO) for 12 min at room temperature. Sections were stained with hematoxylin, dehydrated, and coverslipped using DPX mountant (BDH Laboratory Supplies, Poole, U.K.). Additional sections were stained in the absence of primary antibodies or with irrelevant, isotype-matched control monoclonal antibodies, as negative controls. As positive controls to confirm the specificity of F4/80 and TIB120, sections of mouse spleen, gut, and uterus were stained, and the expected characteristic pattern of staining was obtained in each tissue.
Slides were examined using an AH-3 light microscope (Olympus) and staining was quantified using Video Pro software (Leading Edge Pty Ltd., Adelaide, Australia). Staining was expressed as the mean percentage of positive staining (DAB) normalized to total staining (DAB + hematoxylin). Four nonoverlapping fields were analyzed within each corpus luteum, with six individual corpora lutea assessed per mouse. Five to six mice were used for each mating group.
Data Analysis
Data are presented as the mean ± SEM. Results for immunohistochemistry were analyzed by a one-way analysis of variance (ANOVA) with a Tukey posthoc test. When data were not normally distributed or the variance was not equal, a Kruskal-Wallis ANOVA on ranks was performed with the Dunn method for multiple comparisons. Serum progesterone and in vitro progesterone secretion data were analyzed by a two-way ANOVA with a Tukey posthoc test. A log10 transformation was carried out prior to performing the two-way ANOVA if data were not normally distributed. Significance was assigned at P < 0.05.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
To determine whether uterine exposure at mating to sperm or seminal plasma was able to influence macrophage abundance within corpora lutea, ovaries removed from females mated to intact, vasectomized, or seminal vesicle-excised males were assessed for the presence of macrophages within newly formed corpora lutea by immunolocalizing macrophage markers on the day after mating (Day 1) and also at the expected time of implantation of the embryo (Day 4). On Day 1, positive staining was observed for both F4/80 antibodies (expressed by monocytes and macrophages) and MHC class II antibodies (expressed by activated macrophages and dendritic cells) for all three mating groups. Staining patterns were comparable for both antibodies with labeled cells distributed throughout the corpus luteum. The abundance of labeled cells was similar in corpora lutea of mice mated to intact and vasectomized males (Fig. 1, A and B). F4/80 and MHC class II-positive cells were more sparsely distributed in corpora lutea of mice mated to seminal plasma-deficient males (Fig. 1C). At Day 4, a similar result was observed, with a lower abundance of positively stained cells apparent in corpora lutea of mice mated to seminal plasma-deficient males compared with females mated with intact or vasectomized males (Fig. 1, D– F).
|
The positive staining within corpora lutea was quantified using computer-assisted image analysis. On Day 1, the percentage of positive staining was equivalent in corpora lutea of mice mated with intact and vasectomized males for both antibodies (10% for F4/80 and 8% for MHC class II; Fig. 2, A and B). In the corpora lutea of mice mated with seminal plasma-deficient males, the percentage of positive staining was approximately half that in the other groups, which was a significant decrease for both antibodies (P < 0.05). On Day 4, the proportion of positively stained cells remained lower in corpora lutea of mice mated with seminal plasma-deficient males compared with corpora lutea from mice mated with intact and vasectomized males, although this was not significant (P > 0.05; Fig. 2, C and D).
|
Effect of Mating Type on Progesterone Production During Luteinization
To determine whether the effects of seminal plasma deficiency on macrophage abundance within corpora lutea were associated with a change in progesterone production, serum progesterone content was measured in female mice mated with intact, vasectomized, or seminal vesicle-excised males. Results from unmated mice (at equivalent days postovulation to mated mice) were also included to serve as a reference progesterone levels in the absence of pregnancy or pseudopregnancy. Unlike the macrophage localization data, there were no significant differences between serum progesterone concentration in mice mated with intact, vasectomized, or seminal vesicle-excised males, on either Days 1, 2, or 4 (P > 0.05; Fig. 3). As expected, progesterone concentration in mated mice was highest on Day 4, with levels on Day 2 being higher than on Day 1. In the unmated control group, progesterone concentration had returned to low levels by Day 4, consistent with luteolysis occurring at this time point in corpora lutea from unmated mice.
|
To provide a more sensitive method for detecting progesterone output of corpora lutea, ovaries of mice were dissected and individual corpora lutea were excised and cultured in groups of two for 2 h with or without LH, after which time the culture supernatants were assayed for progesterone concentration. An initial time course experiment revealed that progesterone was secreted by corpora lutea in a linear fashion up to 6 h, and so the 2-h incubation period chosen was within the linear range (data not shown). As shown in Figure 4A, progesterone secretion in basal media by corpora lutea recovered on Day 1 from mice mated with seminal plasma-deficient males was approximately 50% lower than that of corpora lutea from mice mated with vasectomized males, however, this decrease was not significant (P > 0.05). LH induced a significant increase in progesterone secretion by approximately 50-fold for each of the four treatment groups (P < 0.001), but no difference in the LH-induced progesterone levels was observed among groups.
|
In vitro progesterone secretion of corpora lutea was also examined on Day 4. In the absence of LH, progesterone secretion was about 40-fold higher by corpora lutea from mated mice compared with unmated mice, similar to the pattern observed for serum progesterone (P < 0.001; Fig. 4B). Unlike serum progesterone levels, however, in vitro progesterone secretion by corpora lutea recovered from mice mated with seminal plasma-deficient males was significantly higher than the intact group (P < 0.05). LH induced a significant increase in progesterone secretion in all groups except the group mated with seminal plasma-deficient males.
Effect of Mating Type on Progesterone Production During Luteolysis
The significantly higher in vitro secretion of progesterone by corpora lutea from the group of mice mated with seminal plasma-deficient males compared with the intact group on Day 4, suggested that seminal plasma may negatively regulate progesterone production at this time point. This raised the possibility that seminal plasma has a role in promoting luteolysis in the absence of pregnancy. Serum progesterone levels were therefore measured in females mated with intact, vasectomized, or seminal vesicle-excised males on Day 6 and Day 9 after mating, which are time points toward the end of pseudopregnancy [9]. Figure 5 shows that on Day 6, there was no significant difference between the three groups, indicating that luteolysis was not yet occurring, and that there was no effect of seminal plasma deficiency. On Day 9, serum levels of progesterone in the groups of mice mated with vasectomized and seminal plasma-deficient males were only about one-tenth of the level in the intact group (P < 0.001), confirming that luteolysis was taking place in these mice. No significant difference was observed between these two pseudopregnant groups (P > 0.05; Fig. 5).
|
Despite the semen of seminal plasma-deficient mice containing sperm, very few females mated with these males become pregnant, as indicated by the low proportion of mice exhibiting embryos in oviductal flushings (Day 2) or with embryos implanted in the uterus (Day 6 and Day 9) following mating (Table 1). However, pseudopregnancy was successfully induced in all females mated with seminal plasma-deficient males, as indicated by the sustained levels of serum progesterone after mating (Fig. 3).
|
Effect of Mating Type on Ovulation
Despite seminal plasma deficiency having an effect on macrophage abundance within corpora lutea, experiments showed progesterone levels during luteinization or luteolysis were not affected. Macrophages have been shown to influence ovulation rate as depletion of ovarian macrophages decreases the number of ovulated oocytes [22]. The number of ova recovered from oviducts on the day after ovulation was therefore counted in mice mated with intact, vasectomized, and seminal vesicle-excised males, as well as in unmated mice. As shown in Table 2, there was no significant difference in the number of oocytes collected in each of the four groups (P > 0.05), with approximately 7– 8 ova in total recovered from both oviducts of all mice. To examine whether there were differences in the number of ovulation sites on ovaries between the groups, corpora lutea were counted under a dissecting microscope. Because corpora lutea were large and sufficiently vascularized for easy detection on Day 4 after mating compared with Day 1, ovaries were collected from mice at this time point. There was no significant difference between groups (Table 2).
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Macrophages are present within the theca of developing follicles, and their numbers increase at ovulation [3]. Our findings of fewer macrophages within corpora lutea on the day after mating with seminal plasma-deficient males implies that seminal plasma acts to mediate the recruitment of macrophages into either the preovulatory follicle or the developing corpus luteum, depending on whether mating occurs before or after ovulation. Studies have shown that mice maintained under a regular light/dark cycle usually ovulate around or just after the midpoint of the dark phase, depending on the strain [18], and that when housed with a male, mating usually occurs some 2–5 h prior to ovulation [23, 24]. This suggests that the effects of seminal plasma at mating would affect preovulatory follicles.
The mechanism for macrophage attraction to preovulatory follicles following seminal plasma exposure is not known, but it may involve upregulated expression of monocyte chemotactic protein-1 (MCP-1) within follicles, which has previously been shown to act as a chemoattractant for macrophages within corpora lutea of rats [25]. Alternatively, the cytokines granulocyte macrophage-colony stimulating factor (GM-CSF) and macrophage-colony stimulating factor (M-CSF), or other chemokines such as RANTES and MIP1
may be responsible. The corpora lutea of mice deficient in M-CSF have markedly fewer F4/80-positive macrophages [8] and the ovaries of mice deficient in GM-CSF have fewer MHC class II-positive cells [9]. These cytokines are among several shown to be induced by semen and to mediate recruitment of macrophages into the uterus of mice following mating [26–28], but the effects of semen on ovarian cytokine expression remain to be explored.
That seminal plasma exposure of the uterus (or lack thereof) can influence the anatomically distant ovary is a novel finding, and has only previously been shown with regard to advancing the timing of ovulation in pigs [12]. The mechanism and route of signal transfer from the uterus to the ovary has not been established. One plausible postulate involves a countercurrent mechanism whereby a signaling mediator, possibly prostaglandin E2 produced by uterine epithelial cells, diffuses from the uterine vein into the ovarian artery to reach the preovulatory follicles. This vascular communication route is responsible for transporting prostaglandin F2 from the uterus to the ovary in sheep to signal luteolysis [29]. Whether this countercurrent system exists in rodents is not known, nor is the identity of any molecular messenger traveling from the uterus to the ovary. The additional possibilities of seminal fluid efflux via the oviduct to exert local effects in the ovary, or lymphatic connections between the uterus and ovary allowing trafficking of inflammatory cells, also remain to be explored. The finding in pigs that seminal plasma influences the ovary ipsilateral but not contralateral to a uterine horn exposed to seminal plasma [12] supports a local, direct communication rather than a systemic endocrine effect.
The proposed stimulatory role of seminal plasma in mediating recruitment of macrophages into preovulatory follicles is transient and appears to abate by Day 4, when the differential effects of semen composition on macrophage numbers in mice were less pronounced than on Day 1. In view of previous studies in cytokine-null mutant mice linking macrophages with steroidogenesis [9], this observation indicated a possible role for macrophages in progesterone synthesis during the early stages of luteinization. However, serum progesterone levels on Days 1, 2, and 4 were similar in females mated with either males deficient in seminal plasma or with intact and vasectomized males, indicating no effect of seminal plasma on this endocrine parameter of ovarian function during luteinization. Presumably, the effects of seminal plasma on macrophage abundance operate above the threshold required for optimal progesterone production.
Macrophages may also contribute to luteolysis, because their abundance within corpora lutea has been shown to increase during transition into the luteolytic phase [30]. Macrophages have been reported to promote luteolysis via secretion of cytokines that inhibit steroidogenesis [31]. In the absence of pregnancy, seminal plasma exposure during mating may augment the luteolytic process via activity of macrophages. Such a mechanism could accelerate the demise of corpora lutea to allow commencement of the next estrous cycle and maximize the opportunity for subsequent pregnancy. However, our observations made in late pseudopregnancy (Day 9 after mating) demonstrated similar serum progesterone levels between the two groups, suggesting the kinetics of corpus luteum demise late in pseudopregnancy were similar regardless of whether the uterus was exposed to seminal plasma.
Another role for the apparent macrophage recruitment into follicles by seminal plasma at mating could be in facilitating ovulation. However, we find no evidence for this, as there was no effect of seminal plasma deficiency on the number of ova recovered from oviducts on the day after ovulation, or on the number of corpora lutea found on ovaries. A role in remodeling of the preovulatory follicle into a corpus luteum is also possible, because macrophages secrete proteases, including elastase, collagenase, stromelysin, and gelatinase, that potentially mediate degradation of extracellular matrix molecules during rupture of the follicle wall (reviewed in [4]). Additionally, ovarian macrophages have been shown to actively participate in phagocytosis toward the end of the luteal life span [32] and so may also be involved in phagocytosing cellular and matrix remnants during luteinization. Furthermore, macrophages may contribute to the process of angiogenesis via production of growth factors such as vascular endothelial growth factor and other secretory products such as substance P and prostaglandins [33].
Further studies are required to evaluate the relationship between F4/80-positive and MHC class II-positive cells in the corpus luteum, but an emerging understanding of macrophage heterogeneity in other mucosal [34] and reproductive tract tissues [35] suggests that these markers likely identify distinct subpopulations of recently recruited immature macrophages, activated mature macrophages, and dendritic cells. That mating of female mice to males deficient in seminal plasma decreases the abundance of both F4/80-positive and MHC class II-positive cells indicates likely effects both on monocyte recruitment from the blood and on the process of activation and maturation that follow. A final potential role for these cells in the early corpus luteum may be in the regulation of immune tolerance to remnant oocyte antigens that require active immune tolerance to prevent induction of autoimmunity [36].
On Day 1 after mating, LH stimulated a large increase in progesterone output of cultured corpora lutea, demonstrating the robust responsiveness to regulatory stimuli of nascent corpora lutea. LH-induced progesterone secretion by corpora lutea in vitro has previously been demonstrated in mouse and other species [37–39]. Despite corpora lutea from unmated mice on Day 4 after ovulation appearing relatively anemic and having low basal levels of progesterone secretion, they were still able to respond to LH with a strong increase in progesterone output, demonstrating that these corpora lutea still possess the ability to synthesize or secrete (or both) large amounts of progesterone. In fact, the percentage increase in response to LH was much greater than observed in active corpora from mated mice (a 50-fold increase for unmated mice compared with an approximately 2-fold increase for mated females). Thus it appears that the capacity to increase progesterone output in response to LH is inversely related to basal progesterone synthesis. The mechanism for this observation may be a saturation of progesterone synthesis pathway components in active corpora lutea from mated mice, which restricts the maximum secretion level of progesterone in response to an external stimulus. This proposal is supported by the observation that LH-induced levels of progesterone secretion were similar between all four groups.
Only a small proportion of female mice mated with seminal vesicle-excised males became pregnant, as examined on Days 2, 6, and 9 after mating. It has been previously shown in both mice and rats that the fertility of seminal vesicle-excised males is severely diminished, with only 7% and 0% of female mice and rats, respectively, bearing a litter after mating with seminal plasma-deficient males [17, 40]. Because the low pregnancy rate was observed as early as Day 2, the likely reason is impaired fertilization or early embryonic development. In golden hamsters, a deficiency in secretions from the seminal vesicles as well as the prostate and coagulating glands causes retardation in development of the early embryo [41]. In the mouse, a similar developmental block in embryonic cleavage may be occurring following matings deficient in seminal plasma, or there may have been suboptimal rates of fertilization. It has been shown in rats that a normal copulation plug is essential for sperm transport into the uterus [42], and so in the current study in which a plug was not formed after matings with males deficient in seminal plasma, sperm may not have entered the uterus in sufficient quantities to reach the oviduct and fertilize the oocytes. Indeed, it has been reported that only 50% of female mice mated with seminal vesicle-excised males had a concentration of sperm in uterine luminal fluids greater than 106/ml [11]. Which of these mechanisms is responsible for the lower rates of pregnancy in female mice mated to seminal plasma-deficient males has yet to be elucidated.
In conclusion, results of the current study suggest that in the mouse, despite an influence of seminal plasma deficiency on macrophage numbers within corpora lutea, there was no obvious effect of seminal plasma on serum progesterone levels during luteinization or luteolysis, or on ovulation rate. It is likely that seminal plasma has an effect on other parameters of the corpus luteum orchestrated by macrophages such as tissue remodeling, angiogenesis, or immune regulation.
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
2 Correspondence. FAX: 61 8 8222 7521; david.armstrong{at}adelaide.edu.au
Received: 15 January 2004.
First decision: 17 February 2004.
Accepted: 1 June 2004.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
identified as a luteolytic hormone in sheep. Nat New Biol 1972 238:129-134[CrossRef][Medline]This article has been cited by other articles:
|
|
 |
|
  S. A. Robertson, L. R. Guerin, J. J. Bromfield, K. M. Branson, A. C. Ahlstrom, and A. S. Care Seminal Fluid Drives Expansion of the CD4+CD25+ T Regulatory Cell Pool and Induces Tolerance to Paternal Alloantigens in Mice Biol Reprod, May 1, 2009; 80(5): 1036 - 1045. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Tonello and G. Poli Tubal ectopic pregnancy: macrophages under the microscope Hum. Reprod., October 1, 2007; 22(10): 2577 - 2584. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. A. Robertson Seminal fluid signaling in the female reproductive tract: Lessons from rodents and pigs J Anim Sci, March 1, 2007; 85(13_suppl): E36 - E44. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S O'Leary, M J Jasper, S A Robertson, and D T Armstrong Seminal plasma regulates ovarian progesterone production, leukocyte recruitment and follicular cell responses in the pig Reproduction, July 1, 2006; 132(1): 147 - 158. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
