Relationship between maternal plasma progesterone concentration and interferon-tau synthesis by the conceptus in cattle

The objective of this study was to determine the relationship between maternal progesterone concentration and conceptus synthesis of interferon-tau as an index of conceptus viability at the time of maternal recognition of pregnancy. Heifers of mixed beef breeds were randomly assigned to receive 1 of 2 treatments: 1) intramuscular injection of 1500 IU hCG on Day 5 after artificial insemination (AI; n = 12) or 2) intramuscular injection of saline on Day 5 after AI (n = 17). Ovaries were scanned daily by transrectal real-time ultrasonography. Progesterone concentrations were determined from daily blood samples collected from the jugular vein. Heifers were slaughtered on Day 18 after AI and conceptus tissues were collected. These were incubated individually at 37 degrees C in RPMI medium, and supernatant collected after 24 h. Conceptus secretory products in the supernatant were analyzed for interferon concentration by antiviral assay using vesicular stomatitis virus. Transrectal ultrasonography showed all heifers that received hCG had at least 1 extra corpus luteum (CL) in addition to the spontaneous CL formed from the previous ovulation (10 with 2 CL, 2 with 3 CL). A significant increase in plasma progesterone concentration was detected in pregnant heifers treated with hCG (n = 9) vs pregnant control heifers (n = 11; P < 0.001). There was a tendency for an increase (P = 0.059) in synthesis of interferon-tau by conceptuses from hCG-treated heifers compared to control heifers. Maternal plasma progesterone concentrations were correlated with interferon-tau production by the conceptuses (r = 0.593, P < 0.006), suggesting that higher maternal progesterone may provide a more suitable environment for the developing conceptus.     

Relationship between corpora lutea or fetal number and plasma concentrations of progesterone and testosterone in mice

Blastocysts (1-14) were transferred unilaterally into 63 pseudopregnant mice which were killed on Day 17. Plasma progesterone concentrations were significantly (P less than 0.05) lower in animals with one fetus than in those with 2-5 or 9-14 fetuses. Plasma testosterone concentrations were correlated with fetal number in mice with 1-13 fetuses (P less than 0.001). The total placental content of chorionic gonadotrophin in 13 litters varied directly with the number in the litter (1-6), and was 1.67 +/- 0.15 ng/placenta. The number of corpora lutea per mouse was negatively correlated with mean CL volume per mouse (P less than 0.001), and the number of conceptuses was positively correlated with mean CL volume per mouse (P less than 0.001). The effect of conceptuses on the ovary was systemic. The relationship between plasma testosterone concentration and conceptus number may be due to gonadotrophins acting on the ovary, or androgens produced by the placenta or fetus.     

The relationship of conceptus number and fetal sex to maternal serum testosterone concentration in the rat

On Day 8 of pregnancy, the number of implantation sites in pregnant rats was adjusted to 1, 2, 4, 6, or greater than 10. Blood was collected on Days 11, 12, 15, 18, and 20 for the determination of serum testosterone, progesterone, and androstenedione. Serum testosterone levels exhibited a direct linear relationship with implantation number, increasing from 1 through greater than 10 implants. This linear relationship was particularly evident at Days 12, 15, and 18 of pregnancy. Serum progesterone levels increased from one to four conceptuses and plateaued above this number. There was no apparent relationship between the number of conceptuses and serum androstenedione levels, which may reflect the multiple origins of this steroid in the pregnant rat. In a separate group of rats in which the number of conceptuses was adjusted to three on Day 8 of pregnancy, blood was collected on Days 11, 12, 15, 18, and 20. Fetal sex was determined between the last bleeding and the day of parturition. Serum testosterone was determined and results were examined with regard to the number of male/female fetuses in the litter of three. There was no relationship between maternal serum testosterone levels and the number of male fetuses, indicating that the fetal testis does not make a significant contribution to circulating maternal testosterone levels.     

The suppressive effect of the maternal pituitary on relaxin secretion during the second half of pregnancy in rats does not require the presence of the nonluteal ovarian tissue

This study was conducted to determine whether the suppressive effect of the maternal pituitary on relaxin secretion, luteal growth, and progesterone secretion during the second half of pregnancy in rats (Golos and Sherwood, 1984) requires the presence of the nonluteal ovary. At proestrus, rats received unilateral follicular autotransplants to the kidney capsule. These developed into ectopic corpora lutea (eCL) which maintained pregnancy following removal of the in situ ovary on Day 13 of pregnancy. On Day 8, the conceptus number was left unchanged (eCL-5C) or adjusted to 2 (eCL-2C). Serum relaxin levels, eCL relaxin levels, and eCL weights were significantly lower in eCL-2C rats than in eCL-5C rats from Day 12 through Day 20. Following hypophysectomy on Day 13, serum relaxin levels increased significantly in both groups. Mean luteal weights also increased following hypophysectomy of eCL-2C rats. Although not statistically significant, serum progesterone levels tended to be higher in eCL-5C rats than in eCL-2C rats from Day 12 until Day 18; serum progesterone levels tended to increase following hypophysectomy regardless of conceptus number. It is concluded that the presence of the non-luteal components of the ovary are not required for the suppressive effect of the maternal pituitary on relaxin secretion and luteal growth during the second half of pregnancy.     

Inhibitory effects of adrenocorticotrophin or corticosterone on progesterone secretion during mid-pregnancy in rats

Conceptus number was reduced to one on Day 7 of pregnancy in rats by aspirating all but a single conceptus (Group E) or left at greater than or equal to 8 conceptuses (Group C). In Group E rats, serum progesterone concentrations remained low from Day 12 until autopsy at Day 21. Hypophysectomy on Day 12 significantly increased serum progesterone values after Day 17 of pregnancy, and these increases were blocked by treatment with ACTH (10 U/day, i.p., Days 12-17). Adrenalectomy on Day 12 also induced slight, but statistically significant, increases in serum progesterone concentration after Day 17, and these were overcome by implantation of a 10 mg capsule of corticosterone. In Group C rats, hypophysectomy or adrenalectomy on Day 12 did not change serum progesterone concentrations, but 40 U ACTH/day inhibited progesterone secretion. We conclude from these results that the pituitary-adrenal system exerts inhibitory effects on progesterone secretion during mid-pregnancy in rats.     

Evidence for maternal regulation of early conceptus growth and development in beef cattle

Fifty-one cyclic beef cows were mated with fertile bulls. At 36 h after the start of oestrus, cows were assigned to receive sesame oil (controls) or progesterone (100 mg) on Days 1, 2, 3 and 4 of pregnancy. Peripheral plasma concentration of progesterone was measured until slaughter on Days 5 or 14. Cows were randomly assigned to be slaughtered on Days 5 or 14 or remain intact and palpated per rectum on Day 40 to verify pregnancy. Uteri on Days 5 and 14 were flushed for recovery of luminal protein and conceptus tissue. Conceptus and endometrial tissues were cultured with [3H]leucine and submitted to two-dimensional-PAGE and fluorography. Administration of progesterone increased peripheral plasma progesterone concentration on Day 2-5. Conceptuses recovered from progesterone-treated cows on Day 14 were advanced in development compared to conceptuses from control cows. Conceptuses recovered from progesterone-treated cows were viable as polypeptides associated with maintenance of pregnancy in cattle were synthesized and released at an earlier time and pregnancy was maintained beyond Day 40. Early progesterone stimulation altered the synthesis and release of polypeptides from endometrial explant cultures on Day 5. Results indicate a role of progesterone in the maternal regulation of conceptus growth and development in early pregnancy of cattle.     

Synchronous onset of oestradiol-17β secretion by Meishan conceptuses

The response of Meishan conceptuses to an exogenous precursor for oestradiol-17β biosynthesis was investigated in vitro, to determine whether gestational age or morphological stage of development elicit changes in hormone metabolism. Conceptuses were recovered on days 11, 12, 13 or 15 after the onset of oestrus and cultured for 6 hours at 37°C, in the presence or absence of testosterone. On days 12 and 13 after the onset of oestrus spherical conceptuses were recovered from some gilts, whereas others yielded elongated or filamentous conceptuses. All conceptuses recovered on day 15 after oestrus had elongated. The number of cells per individual conceptus increased from days 11 to 13 after the onset of oestrus (P < 0.001), as did conceptus surface area (P = 0.038). Supplementing culture media with testosterone, as a substrate for oestrogen biosynthesis, significantly increased conceptus oestradiol-17β secretion in vitro on days 12, 13 and 15, regardless of whether pre- or post-elongation conceptuses were cultured. However, on day 11 oestradiol-17β was only detected at significant concentrations in the culture media of four testosterone supplemented conceptuses and only one gilt produced conceptuses capable of secreting oestradiol-17β in the absence of testosterone. Therefore, the onset of conceptus oestradiol-17β secretion is apparently limited by the expression of aromatase enzymes that are activated synchronously, irrespective of the stage of morphological development, within Meishan litters. Once established, Meishan conceptus oestradiol-17β secretion in vitro is increased in the presence of exogenous testosterone.     

Detection of fetal gender differences in maternal serum progesterone concentrations of Asian elephants (Elephas maximus)

Previous studies have analyzed total testosterone concentrations in maternal serum for a reliable method of fetal gender determination in Asian elephants (Elephas maximus). The present study investigated the possibility that progesterone concentrations in maternal serum may reflect these testosterone patterns. Weekly serum samples were collected from 17 pregnancies in captive Asian elephants and analyzed via radioimmunoassay (RIA) for progesterone concentrations. Nine and eight cows carried male and female calves, respectively. Mean progesterone concentrations in maternal serum of elephants carrying male calves were greater than in those carrying female calves (P<0.01). Mean progesterone concentrations (based on 5-week means) in maternal serum were greater at weeks 20-55 (P<0.01) and 60-65 (P<0.05) for elephants carrying male calves.     

Effect of progesterone,mifepristone, and estrogen treatment during early pregnancy on conceptus development and uterine capacity in Swine

A series of experiments was performed to investigate the influence of progesterone at Days 2 and 3 of pregnancy on conceptus development and uterine capacity. In experiment 1, unilaterally hysterectomized-ovariectomized (UHO) white crossbred gilts were given no treatment, estradiol valerate (5 mg given on Days 11 and 12), or progesterone (200 mg/day on Days 2 and 3 after mating). On Day 105 of pregnancy, each fetus and its associated placenta were weighed, and the number of live and dead fetuses was recorded for each litter. Early progesterone treatment reduced (P < 0.05) litter size (a measure of uterine capacity in UHO gilts). In experiment 2, intact white crossbred gilts were mated, given no treatment or progesterone treatment on Days 2 and 3 of pregnancy, and farrowed. Progesterone treatment decreased (P < 0.05) pregnancy rates. In pregnant gilts, progesterone had no effect on the number of live or stillborn piglets at birth, and gestation length was decreased (P < 0.05). Progesterone treatment did not affect the number of large or small piglets. In experiment 3, intact gilts were mated at estrus and then received 1). no treatment or treatment with 2). 100 mg, 3). 200 mg, or 4). 400 mg mifepristone (also known as RU486) on Day 2 of pregnancy. On Day 11 of pregnancy, both uterine horns were flushed, the number and diameter of each conceptus was recorded, and the flushed material was assayed for total protein and acid phosphatase. The 400 mg mifepristone treatment decreased conceptus diameter (P < 0.05) and total protein (P = 0.06) in the uterine flushings. In experiment 4, UHO gilts were mated at estrus, injected with either corn oil (control) or mifepristone (400 mg) on Day 2 of pregnancy, and killed on Day 105 of pregnancy, and the number and weight of live fetuses and placentas was recorded. In contrast to the effect of progesterone treatment, mifepristone decreased uterine capacity by decreasing the number of small conceptuses. These data suggest that progesterone concentrations on Days 2 and 3 of pregnancy in swine influence the rate of conceptus development during early pregnancy and uterine capacity during later pregnancy.     

Steroid metabolism by endometrial and conceptus tissues during early pregnancy and pseudopregnancy in gilts

Endometrial and conceptus tissues were obtained on Days 10.5, 11, 12, 16 and 25 of pregnancy and Day 25 of pseudopregnancy of gilts and incubated for 6 h in Minimal Essential Medium (5 ml) containing 35 ng [3H]progesterone. Metabolism of [3H]progesterone to oestrone, oestradiol and oestriol was determined by gas and high-pressure liquid chromatography and successive recrystallizations with unlabelled standards. Conceptuses collected between Days 10.5 and 12 were spherical, tubular or filamentous and incubated with 500 mg endometrium and [3H]progesterone. Production of oestrone by spherical conceptuses was not detected, but was 44-47 pg/tubular conceptus and 21 pg/filamentous conceptus. A similar trend was observed for oestradiol. Conceptus tissues from Days 16 and 25 (chorion) were most active in producing oestrone (123 and 520 pg/mg tissue, respectively) and oestradiol (277 and 876 pg/mg tissue, respectively). Endometrial oestrogen production was less than that for conceptus tissue for oestrone and oestradiol on Days 16 and 25 of gestation. Coincubations of endometrium and conceptus tissues had lower oestrogen production than conceptus alone. Endometrium from Day 25 of pseudopregnancy metabolized [3H]progesterone to several non-polar metabolites, but no oestrogens were detected. An unidentified phenolic metabolite of [3H]progesterone was detected in higher quantities than either oestrone or oestradiol; 445 to 461 pg/conceptus at the tubular stage. These results indicate temporal changes in the conversion of [3H]progesterone to oestrogens by conceptus and endometrial tissue from pregnant gilts, but not endometrium from pseudopregnant gilts.     

Trophoblast giant cell release of placental lactogens: temporal and regional characteristics

Placental lactogen (PL) production by rat trophoblast giant cells was studied using in vitro methods. The influence of trophoblast giant cell location within the conceptus and day of trophoblast giant cell isolation on the type of PL released in vitro were investigated. The effect of trophoblast giant cell location on the amount of PL, progesterone, and testosterone released in vitro was also evaluated. Trophoblast giant cells release two types of PLs in vitro; a high-molecular-weight lactogen, PL-1, and a low-molecular-weight lactogen, PL-2. The type of PL released by trophoblast giant cells was not influenced by their location within the conceptus at the time of dissection. Location did influence the amount of hormone produced by trophoblast giant cells. Mural trophoblast giant cells were more active in the production of PL, progesterone, and testosterone. The type of PL released by trophoblast giant cells is highly dependent upon the day of gestation the cells are removed for study. Trophoblast giant cells isolated on Day 10 of gestation release predominantly PL-1, while those cells isolated 24 hr later (Day 11 of gestation) release predominantly PL-2. The switch from PL-1 to PL-2 production that occurs in vivo does not occur under the in vitro conditions employed in this report.     

Hormonal correlates of 'masculinization' in female spotted hyaenas (Crocuta crocuta). 2. Maternal and fetal steroids.

Concentrations of androgens (androstenedione, testosterone, 5 alpha-dihydrotestosterone), oestrogen and progesterone were measured in relation to pregnancy in the spotted hyaena (Crocuta crocuta). The gestation period was estimated to be about 110 days. There was a marked progressive rise in all the steroids starting in the first third of gestation. Chromatographic separation of plasma showed that much of the oestrogen is not oestradiol (only 12% of total measured) and that a significant fraction of the 'testosterone' may be dihydrotestosterone. In the final third of pregnancy, concentrations of androgen (especially testosterone plus dihydrotestosterone) in the female circulation reached the maximal values of adult males; the percentage of dihydrotestosterone relative to total testosterone plus dihydrotestosterone was higher in females (44 +/- 3.9%, n = 20) than in males (29.5 +/- 3.5%, n = 17). Plasma androstenedione was also significantly higher in females, but the increment was less than for oestrogen, testosterone and progesterone, and the temporal pattern was less clear. Samples from the maternal uterine and ovarian circulation showed that androstenedione is largely of ovarian origin and metabolized by the placenta, while testosterone, progesterone and oestrogen are primarily of placental or uterine origin. Fetal samples were taken from two mixed-sex sets of twins and one male singleton. Gradients across the placenta measured in the fetal circulation confirmed that the placenta metabolizes androstenedione and is a source of testosterone for the female fetus; there were no consistent differences in androgens between male and female fetuses. It is suggested that the conspicuous masculinization of the female spotted hyaena, especially evident in the external genitalia at birth, is a result, at least in part, of high placental production of testosterone or dihydrotestosterone derived from the metabolism of high maternal androstenedione.     

Effects of aggressive encounters on plasma corticosteroid-binding globulin and its ligands in white-crowned sparrows

In birds, corticosteroid-binding globulin (CBG) binds corticosterone, progesterone and testosterone. The concentration of each ligand can alter the binding of the other ligands through competitive interactions. Thus, an increase in corticosterone or progesterone may displace testosterone bound to CBG, leading to an increase in bioactive free testosterone levels without affecting total testosterone levels in the circulation. Aggressive interactions increase plasma total testosterone levels in some birds but not in others. Here, we tested the hypothesis that aggressive encounters in the late breeding season would not increase total testosterone levels in plasma, but would alter CBG, total corticosterone or total progesterone levels in such a way as to modify the number of available binding sites and therefore occupancy by testosterone. A marked decrease in CBG occupancy by testosterone would indirectly suggest an increase in free testosterone levels in plasma. Wild male white-crowned sparrows were exposed to a simulated territorial intrusion (STI) or control for 30 min. Subjects were then caught and bled. We measured CBG using a ligand-binding assay and corticosterone, progesterone and testosterone using highly sensitive radioimmunoassays. STI significantly increased aggressive behaviors but did not affect plasma total testosterone levels. STI significantly increased plasma CBG and total corticosterone levels and decreased plasma total progesterone levels. We predict that CBG occupancy by corticosterone will increase slightly following an aggressive encounter. However, this small change is unlikely to increase free testosterone levels, because of the large number of seemingly unoccupied CBG binding sites in these subjects.     

Maternal recognition of pregnancy in the rabbit

Conceptuses were removed by extrusion through incisions in the uterus on Days 11, 12 and 18 post coitum (p.c.). Pseudopregnant does at Days 11 and 12 and pregnant does at Day 18 were sham-operated and served as controls. Blood samples were collected before and daily for 3 days after conceptus removal. Serum progesterone profiles of does whose conceptuses were removed on Day 11 p.c. were identical to those of intact pseudopregnant and sham-operated pseudopregnant controls. Conceptus removal on Days 12 or 18 p.c. resulted in a precipitous decline (P less than 0 X 01) in progesterone levels within 48 h. LH levels were low (less than 1 ng/ml) in all groups before and after surgery and there were no significant differences between treated and control rabbits. These data demonstrate that the maternal recognition of pregnancy occurs by Day 12 of gestation and that conceptus removal does not result in an alteration in serum LH levels.     

Relationship of conceptus number to the action of luteinizing hormone-antiserum in the pregnant rat

Treatment of pregnant rats on Day 12 of pregnancy with luteinizing hormone-antiserum (LH-AS) (equine anti-bovine LH) had no effect on the maintenance of pregnancy or serum progesterone levels in rats bearing either 2 or more than 8 conceptuses. In rats with only 1 conceptus, LH-AS administration resulted in a significant decline in serum progesterone to basal levels within 24 h and all animals (n = 6) failed to maintain pregnancy. All rats with either 1, 2 or greater than 8 implantations showed no effect of normal horse serum (NHS) administration. There was no effect of LH-AS administration on serum testosterone levels, compared to NHS-treated controls.     

Relationship between functional activity of the adrenal glands and gonads in monkeys during puberty]

Testicular and adrenal cortex endocrine functions were simultaneously tested in pubertal baboons (papio hamadryas) during one year. Concentrations of androgens (testosterone, 5 alpha-dihydrotestosterone, dehydroepiandrosterone), corticosteroids (cortisol, progesterone, 17-hydroxyprogesterone, 17-hydroxypregnenolone) and aldosterone were determined in blood of the experimental monkeys by radioimmunoassay. It was shown that with increasing androgen (testosterone and dihydrotestosterone) levels in blood of the pubertal monkeys there was a significant decrease of corticosteroid concentration which was most pronounced in the monkeys with maximum increase of testosterone level. Described hormonal changes did not influence aldosterone concentration.     

Copulatory behaviors and body condition predict post-mating female hormone concentrations, fertilization success, and primary sex ratios in Japanese quail

Environmental cues and social interactions are known to influence reproductive physiology and behavior in vertebrates. In female birds, male courtship displays can result in the growth of ovarian follicles, the production of reproductive hormones, and stimulation of oviduct development, all of which have the potential to influence maternal investment. Male Japanese quail follow a typical sequence of copulatory behaviors during a mating interaction and often force copulations with unreceptive females. We hypothesized that female Japanese quail could adjust maternal investment in response to male copulatory behaviors during a single mating interaction. We investigated the relationships between 1) male copulatory behaviors and post-mating concentrations of steroids in the female, 2) female steroid concentrations and fertilization success of inseminations and 3) female steroid concentrations and the offspring sex ratio. We found that male condition and copulatory behaviors predicted female steroid concentrations and maternal investment in eggs laid after a mating trial. The body condition of one or both mates was a significant predictor of the changes in female corticosterone and testosterone concentrations after mating, whereas specific male copulatory behaviors significantly predicted changes in female progesterone concentrations. Male and female body condition, male neck grabs and post-mating concentrations of female corticosterone, progesterone, and testosterone were all significant predictors of egg fertilization rates. Female body condition, male copulation efficiency, and female testosterone concentrations were significant predictors of offspring sex ratios. Our results show that phenotypic and behavioral characteristics of male Japanese quail modulate female steroid concentrations and result in changes in maternal investment.     

Comparison of PGF2α-induced luteolysis in early pregnant and estrogen-treated ‘pseudopregnant’ gilts

Conceptus estrogen clearly plays a major role in luteal maintenance in the pig; however, other conceptus-derived substances or conceptus-induced uterine secretory products appear to have a local luteotrophic/anti-luteolytic effect on the corpora lutea (CL) and likely may play a key role in maternal recognition of pregnancy in the pig. The objective of these studies was to compare PGF₂α-induced luteolysis in estrogen-treated ‘pseudopregnant’ gilts versus pregnant gilts during the period of maternal recognition of pregnancy. In Experiment 1, doses of PGF₂α ranging from 1 to 100 μg were administered via intraluteal silastic implants to pseudopregnant gilts to determine the dose necessary to cause functional (progesterone) and structural (weight) luteal regression similar to that observed during the natural estrous cycle. Luteal sensitivity to this minimally effective luteolytic dose of PGF₂α was then determined for both pseudopregnant and pregnant gilts in Experiment 2. Experiment 3 investigated whether Day 13 porcine conceptus tissue could directly prevent PGF₂α-induced luteolysis at the level of the CL. The minimally effective luteolytic dose of PGF₂α (100 μg) determined in the pseudopregnant pig caused a similar decline in progesterone concentration and weight of CL in pregnant gilts, suggesting that the susceptibility of CL of pregnant and pseudopregnant pigs to PGF₂α is similar. However, luteal weight was greater (P<0.05) for the pregnant gilts than for pseudopregnant gilts, suggesting that estrogen treatment alone cannot mimic the conceptus effects on CL growth and development. Experiment 3 demonstrated that lyophilized Day 13 conceptus tissue implanted directly into individual CL could partially inhibit PGF₂α-induced luteolysis, providing for the first time direct evidence that porcine conceptuses as early as Day 13 contain factors which can directly (i. e. at the level of the CL) prevent luteal regression.     

Progesterone inhibits rejection of xenogeneic transplants in the sheep uterus

OBJECTIVES: One of the proposed roles of progesterone is to prevent maternal immunological destruction of the allogeneic conceptus. Here, it was demonstrated that progesterone allows survival of a xenotransplant placed in the uterine lumen. METHODS: Ovariectomized ewes, surgically prepared to have ligatures around each uterine horn, were given daily subcutaneous injections of 50 mg progesterone or vehicle (sesame oil). After 30 days of treatment, mouse hybridoma cells were transplanted to one ligated uterine horn and phosphate-buffered saline was injected into the other horn. The uterus was flushed after an additional 14 days of treatment and hybridoma cells were identified by immunofluorescence. RESULTS: Overall, hybridoma cells were recovered from 4 of 5 progesterone-treated ewes and 1 of 5 vehicle-treated ewes. Immunohistochemical analysis of intercaruncular endometrium using antibodies towards CD8, gammadelta, and CD45R lymphocyte markers revealed that local presence of hybridoma cells caused a significant increase in CD8+ cells in all tissue compartments. While not significant, the numbers of CD8+ cells in the luminal and glandular epithelium were lower for progesterone-treated ewes. Progesterone tended to increase gammadelta T cell numbers in the glandular epithelium. CONCLUSIONS: Results demonstrate that xenograft rejection in the uterus is associated with an increase in CD8+ cells in the endometrium and that progesterone can inhibit uterine tissue graft rejection responses sufficiently to allow survival or delay rejection of xenograft tissue.