Corpus Luteum Of Pregnancy Research Articles

Circulating steroids and the relationship between ovarian and placental secretion during early and mid pregnancy in the baboon.

Ovarian and placental steroid secretion was examined at intervals during early and mid-pregnancy in the olive baboon, Papio anubis. Progesterone, androstenedione, testosterone, estrone, and estradiol-17β were measured after celite chromatography in samples from peripheral circulation and from utero-ovarian veins draining ovaries with and without corpora lutea at the following stages of pregnancy: days 8-9 (unconfirmed pregnant), 10-19, 34-40, 60-66, and 104-106 after ovulation. The pattern of hormone levels in peripheral and utero-ovarian vein samples indicated the following: 1) The corpus luteum was the principal source of progesterone until at least day 19. Placental secretion was well advanced by days 34-40 and provided the major contribution to circulating progesterone levels by day 60.2) There was a significant elevation in peripheral concentrations of androstenedione and testosterone on days 10-19 and 34-40 of pregnancy; androgen levels in peripheral and utero-ovarian vein samples declined to baseline values by day 60. 3) Estrogens were secreted by the corpus luteum on days 10-19 but not on days 34-40. Placental secretion of estradiol-17β increased markedly after days 60-66, whereas little, if any, placental secretion of estrone was apparent at this time. These results provide circumstantial evidence that progesterone secretion by the corpus luteum of early pregnancy extends beyond the time when estrogen secretion has declined and that the timing of the luteo-placental shift in the baboon is intermediate between that in rhesus monkeys and that in marmosets and humans. Increased secretion of androgens during the first 6 weeks of gestation may be useful in early pregnancy diagnosis in the baboon, although the physiological significance of this event is not clear.

Corpora lutea of pregnancy and elevated serum progesterone during pregnancy and postpartum anestrus in woodchucks (Marmota monax).

Serum samples (n = 62) were collected from wild-caught woodchucks (n = 45) that were nonpregnant (n = 3), pregnant (n = 25) or postpartum (n = 34) when bled at the time of capture and/or necropsy, or following maintenance and observation for variable periods of time. Progesterone concentrations were determined by radioimmunoassay and related to the actual or estimated time from parturition which occurs at 31 days postcoitum in this species. Mean serum progesterone levels during the initial, middle and last third of pregnancy were 6.5 +/- 1.7, 22.5 +/- 3.7 and 16.8 +/- 3.2 ng/ml, respectively. Postpartum progesterone levels were elevated above basal values (less than or equal to 0.3 ng/ml) in both lactating and nonlactating animals for 2-3 months postpartum and were not consistently basal until more than 90 days postpartum. Mean progesterone levels at less than 30, 30-60, 61-90, and greater than 90 days postpartum were 25.1 +/- 6.2, 60.6 +/- 18.5, 22.8 +/- 8.7 and 0.4 +/- 0.2 ng/ml, respectively, and those at 30-60 days postpartum were greater than those at midpregnancy (P less than 0.05). Mean corpus luteum diameters were also greater (P less than 0.05) postpartum (2.9 +/- 0.3 mm) than during pregnancy (1.5 +/- 0.3 mm). The correlation between placental scars and ipsilateral corpora lutea indicated that the corpora lutea observed postpartum were the corpora lutea of the recent pregnancy. The termination of each uterine horn in a separate external cervical os precluded the occurrence of transcornual migration.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between ovarian and placental steroid production during early pregnancy in the marmoset monkey (Callithrix jacchus).

Concentrations of progesterone, 17 alpha-hydroxyprogesterone, oestrone and oestradiol-17 beta in peripheral and utero-ovarian vein blood were measured during the first 60 days of pregnancy. The same hormones were also measured in peripheral blood samples from non-fertile cycles. Peripheral levels of 17 alpha-hydroxyprogesterone, oestrone and oestradiol increased gradually during early pregnancy whereas concentrations of progesterone declined. The patterns of secretion of progesterone, 17 alpha-hydroxyprogesterone and oestrone, but not oestradiol, were significantly different in fertile and non-fertile cycles by 15 days after ovulation. Comparison of hormone values in peripheral and utero-ovarian vein samples from ovaries with and without corpora lutea (Days 7, 9, 13, 21, 40 and 60 of pregnancy) showed that: (a) progesterone was secreted by the corpus luteum until at least Day 40 by which time there was also placental secretion; (2) although 17 alpha-hydroxyprogesterone was secreted by the corpus luteum, the relative contribution of luteal and placental secretion after Day 21 was not clear; (3) oestrone secretion by the corpus luteum was no longer detectable by Day 40, but placental oestrone secretion appeared to be present by this time; (4) the corpus luteum did not secrete significant amounts of oestradiol at any stage of early pregnancy, although there was evidence for placental secretion by Day 40. These results suggest that progesterone secretion by the corpus luteum of early pregnancy continues beyond the time when oestrogen secretion has declined. The corpus luteum to placental shift in the marmoset appears to occur at a later stage of pregnancy than it does in the macaque monkey and probably also in man.

Hormonal changes in post-partum blood plasma and milk of buffaloes (Bubalus bubalis)

ABSTRACTPost-partum changes in the concentration of progesterone, oestradiol-17β and prolactin were measured by radioimmunoassay in the blood plasma and milk of 28 buffaloes. The mean concentration of progesterone in the plasma of normal animals was 0·24 ± 0·04 μ.g/1 on the day of calving and decreased linearly during the post-partum period, until the complete regression of the residual corpus luteum of pregnancy occurred, when the plasma concentration was recorded as 0μ05 to 0μ08 μg/l. The concentration at a silent oestrus was 0μ17 ± 0·02 μ.g/1. The milk progesterone profile was parallel to that of plasma but the level was 2 to 4 times higher.The mean concentration of oestradiol-17β in plasma was 41·0 ± 2·34 ng/1 on the day of calving; it declined significantly by day 1 post partum (P < 0·001) and fluctuated between 8 and 16 ng/1 until oestrus, when the concentration was approximately 25 ng/1. The oestradiol-17β concentration in milk was significantly higher than that of plasma on the day of calving. During the first 20 days post partum, a similar concentration of oestradiol-17β was maintained in both fluids but thereafter the concentration in milk was 2 to 3 times that of plasma.The mean concentration of prolactin in plasma was 212·6± 19·08 μg/1 on the day of calving and then declined and fluctuated between 70 and 270 μg/1 during the rest of the period. A minor elevation occurred around oestrus. The prolactin concentration for the first 2 days post partum in milk was significantly higher than that in plasma but during the rest of the period it was similar to that in plasma.The progesterone concentrations were slightly lower in anoestrous animals than in those cycling. The concentration of prolactin was significantly higher in multiparous animals (P < 0·001), whilst the progesterone and oestradiol values were similar in primiparous and multiparous animals.

Partial purification of a chorionic gonadotropin-like protein from bovine cotyledons.

The presence of placental gonadotropin activity in early pregnancy was studied in the cow. Cotyledons from the first trimester of gestation were used to isolate a chorionic gonadotropin-like (CG-like) protein by means of ammonium sulfate precipitations (0.17-4.5 M) and gel filtration on Sephadex G-100 and DEAE-Sephadex. The CG-like activity was measured by a radioreceptor assay (RRA) specific for human chorionic gonadotropin (hCG). Luteotrophic activity was also assessed in two separate in vitro bioassays using cultures of bovine granulosa and rat Leydig cells. It was found that the 3 M ammonium sulfate precipitate of cotyledon extracts contained a CG-like activity of 179 mIU/mg protein as measured by RRA. The precipitate inhibited 125I-hCG binding in a linear fashion. A ninefold increase in specific activity was achieved by further purification on Sephadex G-100 (800 mIU/mg protein) and Sephadex-DEAE (1600 mIU/mg). In experiments with cell cultures, it was found that 20 micrograms of protein eluted from Sephadex-DEAE (equivalent to 16 mIU of hCG as determined by RRA) added to the culture medium significantly enhanced (P less than 0.05) progesterone production by the granulosa cells and testosterone production by the Leydig cells. We conclude that the bovine placenta contains a chorionic gonadotropin which may serve to maintain the corpus luteum of pregnancy.

Post partum ovarian activity and uterine involution in the suckled swamp buffalo ( Bubalus bubalis)

Ovarian activity and uterine involution were monitored by rectal palpation, oestrus detection and plasma progesterone analysis from 3 to 4 days to approximately 150 days post partum in 38 suckled swamp buffaloes ( Bubalus bubalis). The intervals from parturition to regression of the corpus luteum (CL) of pregnancy and involution of the uterus were 10 and 28 ± 6 (S.D.) days respectively. First detected oestrus and first elevation of plasma progesterone (> 0.7 ng/ml) occurred at 88 ± 26 and 96 ± 22 days in 8 and 12 buffaloes respectively. During the first 150 days post partum, 26 of 38 suckling buffaloes (68%) were acyclic (anoestrus) and of 12 animals (32%) exhibiting ovarian cycles, 4 were not detected in oestrus. The tentative diagnosis, based on rectal palpation, that CL were present between days 30 and 90 after parturition (without concurrent luteal levels of progesterone in plasma) suggests that confirmation should be by laparoscopy. It is concluded that a delay in the resumption of ovarian cyclicity post partum represents an important factor contributing to the prolonged calving to conception interval in the suckled swamp buffalo.

Effects of oxytocin on the bovine corpus luteum of early pregnancy.

Summary. Oxytocin, at concentrations of 4 and 40 mi.u./ml, significantly enhanced progesterone production by dispersed bovine luteal cells (0·5–4 months of gestation) after incubation for 3 h. The luteotrophic effect of 4 mi.u. oxytocin/ml was comparable to that of 10 i.u. hCG/ml. Higher oxytocin concentration (800 mi.u./ml) markedly inhibited the response of the luteal cells to hCG and may be inhibitory to basal progesterone production. These data provide evidence for an effect of oxytocin on the bovine corpus luteum of early pregnancy.

Role of the preimplantation embryo in the timing of LH-dependent progesterone secretion from the rat corpus luteum.

AbstractThe effect of the progestational uterus and preimplantation embryo on the time of appearance of LH-dependent progesterone secretion from pregnant and pseudopregnant (PSP) rat corpora lutea (CL) was studied. Two groups of experiments were performed: (1) pregnant and PSP rats were hysterectomized between Days 3 and 5 (Day 1 = vaginal estrus) and subsequently monitored for changes in serum progesterone levels following an injection of LH antiserum (LHAS) or normal horse serum (NHS) vehicle on Day 9 and, (2) Day 4 embryos were transferred to Day 3 PSP uteri; each rat was subsequently hysterectomized on Day 4 of PSP and treated with LHAS or NHS on Day 9. Progesterone levels were monitored as an index of luteal vitality. Progesterone secretion was not altered by NHS treatment in any group. LHAS treatment did not induce luteolysis in Day 3 pregnant rats or in PSP rats hysterectomized on Days 3 or 4. However, in rats hysterectomized on Day 4 or 5 of pregnancy, or hysterectomized on Day 5 of PSP, luteolysi...

Follicular development in primiparous lactating sows

The object of this investigation was to study ovarian activity with particular reference to follicular development in primiparous sows during the lactation period. Thirteen primiparous sows were slaughtered at day 4, 5, 14, 21, 28, 42 or 56 of lactation. The ovaries were examined macroscopically, serially sectioned and photographed. Follicles ⩾ 1 mm were counted and classified as normal or atretic. Corpora lutea of pregnancy were identified and the size measured. The peripheral plasma progesterone levels were determined throughout the lactation period. There was a tendency towards increasing numbers of normal and atretic follicles of 2.00–4.99 mm size during later stages of lactation. During the first week of lactation there was an accumulation of atretic follicles. About equal numbers of normal and atretic follicles were recognized at days 14, 21 and 28 of lactation. There were more normal than atretic follicles at days 42 and 56. The peripheral plasma progesterone levels were constantly low in all sows, indicating that no ovulation occurred during lactation. It can be concluded that the ovaries had some development in follicular growth during lactation but they did not reach the ovulatory size.

In vivo and in vitro production of progestins by the corpus luteum of pregnancy of the hamster.

Synthesis by hamster corpora lutea (CL) in vitro and serum levels of progesterone (P4), 17 alpha-hydroxyprogesterone (17OHP) and 20 alpha-dihydroprogesterone (20DHP) were assessed for different days of pregnancy (Day 1=day of sperm; Day 16=day of delivery). Highest serum levels of the progestins were observed on Day 14 (P4=33 ng/ml; 17OHP=2 ng/ml; 20DHP=3 ng/ml), followed by precipitous declines on Day 16. The highest in vitro levels of luteal P4 and 17OHP were attained on Days 2-6 (production rates of P4=9-30 ng/mg CL/h; 17OHP=0.6-1.5 ng/mg CL/h), and dropped gradually thereafter. In contrast, the production rate of luteal 20DHP was extremely low on Days 2-8 but abruptly increased on Day 10 and was maintained through Day 14 (4-8 ng/mg CL/h). The in vitro production rates of all 3 progestins dropped abruptly on Day 16. Thus, in the pregnant hamster on the day of parturition (Day 16) there was good agreement between in vivo and in vitro levels of the progestins, contrary to the situation in the rat, where on Day 22 the CL in vitro produce large quantities of P4 and 20DHP while the serum levels are very low (Taya and Greenwald, 1981). Addition of 25 ng/ml of ovine LH to the incubation media containing hamster CL increased production rates of P4 (18-55 ng/mg CL/h) and 17OHP (1.5-2.4 ng/mg CL/h) on Days 2, 4 and 14 of pregnancy but the CL were refractory to this dose of LH from Days 6 to 12. The production rate of luteal 20DHP ws never stimulated by the addition of 25 ng LH. These results indicate that P4 is the principal progestin in the pregnant hamster with 17OHP and 20DHP as minor metabolites. The latter 2 progestins have been measured for the first time in the pregnant hamster and the levels are very low in comparison to the pregnant rat.

Effect of embryos on luteolysis and termination of early pregnancy in sheep with cloprostenol.

An investigation of the control of the function of the corpus luteum of early pregnancy in sheep has been carried out by assessing the luteolytic effects of a dose of 100 micrograms of the synthetic prostaglandin, cloprostenol. Cloprostenol injected into 21-day pregnant sheep carrying single or multiple embryos caused luteolysis and termination of pregnancy within 2--5 days in 8 of 23 sheep. The mean numbers of corpora lutea in these ewes differed significantly from those which carried their pregnancy (1.8 +/- 0.3, SEM, vs 3.2 +/- 0.4; P less than 0.05). It appeared that the greater number of embryos, or a greater mass of embryonic tissue, afforded increased protection to the corpora lutea through unidentified antiluteolytic or luteotrophic factors. The number of corpora lutea present did not appear to be an operative factor, as the same dose of cloprostenol was luteolytic in 43 of 46 nonpregnant ewes with 1--6 corpora lutea; the 3 refractive ewes each having only 1 corpus luteum. The progesterone concentration in the plasma of pregnant ewes which underwent luteolysis following cloprostenol treatment was 0.5 +/- 0.1 ng/ml 48 h after injection, while that of the ewes remaining pregnant was significantly higher at 2.1 +/- 0.3 ng/ml. Seven of these refractive ewes which were given a second injection of cloprostenol on Day 28 of pregnancy subsequently experienced luteolysis and abortion. The corpora lutea of the remaining 8 ewes were not affected by saline injections given on Day 28, but 4 of these ewes later aborted after Day 44. It is concluded that pregnancies on ewes carrying 1 embryo can be terminated by a single dose of 100 micrograms cloprostenol given around Day 21 of pregnancy, but 2 injections given about 7 days apart may be needed when multiple embryos are present. Hormonal control of the sensitivity of the corpus luteum to luteolytic prostaglandins appears to reside in the conceptus in such a way that a decrease in sensitivity is related to the number of embryos present.

Rat placental hormones: attempts for identification of rat chorionic gonadotrophin and rat placental lactogen by in vivo experiments.

Abstract. Rat placental extracts (rPE) were investigated in bioassays for their possible content of rat placental lactogen (rPL) and rat chorionic gonadotrophin (rCG). Luteotrophic and lactogenic activity of rPL was assessed by substitution of rats depleted of endogenous prolactin (Prl) by means of bromoergocryptine (BEC) in early pregnancy and the period of lactation, respectively. The abortifacient effect of a single dose of BEC on day 6 of pregnancy was abolished by rPE equivalent to 1 g rat placenta corresponding to 5 IU bovine Prl (NIH-P-B 2). Substitution was necessary until the evening of day 7 indicating that rPL does not take over the function of Prl before day 8. During lactation rPE reversed the lactation inhibiting effect of daily BEC treatment. In this assay rPL activity corresponded to 1.25–2.5 IU bPrl/g placenta. In order to test for the possible existence of rCG the gonadotrophic activity of rPE was assessed in immature female mice. No gonadotrophic activity was found when rPE equivalent to 1 g rat placenta was administered, whereas equivalents of 3 mg human placenta and 12 mg rat pituitary entailed a dose-dependent response. In this system 0.12 IU human chorionic gonadotrophin (hCG), which served as standard, was the minimal dose (MD) resulting in increased uterine weight. In addition rPE was tested in the immature female rat, where the limit of detection was found to be 0.5 IU hCG. Again no gonadotrophic activity was found in rPE. As the effects of rCG might have been restricted to its presumed target, the corpus luteum of pregnancy, rPE was also tested in pregnant rats depleted of endogenous luteinizing hormone (LH) by a single injection of anti-LH antibodies on day 10 of pregnancy. A MDof 0.5 IU hCG, which served as standard, prevented resorption of foetuses in all animals tested. rPE equivalent to 3.5 g rat placenta, rat pregnancy serum of day 18 and placental transplants could not substitute for endogenous LH.

Epinephrine-sensitive adenylyl cyclase activity in rabbit ovarian tissues.

Epinephrine-sensitive adenylyl cyclase (AC) activity was investigated in homogenates of rabbit ovarian tissues. Optimal epinephrine-stimulated AC activity in corpora lutea homogenates was achieved with millimolar concentrations of ATP (1-4 mM) and Mg2+ (2-12 mM) in the absence of exogenously added Ca2+. Epinephrine stimulated the luteal AC under these conditions in a dose-dependent manner, with an ED50 of 0.45 micrograms/ml. The AC of preovulatory follicle homogenates was found to be unresponsive to epinephrine stimulation. Epinephrine responsiveness of the AC slowly appeared in late preovulatory and early postovulatory follicles in response to the gonadotropin surge induced by coitus. By 18 h after mating, epinephrine-stimulated AC activity had doubled, and maximal activities in the newly formed corpora lutea were reached within 72 h. Thereafter, epinephrine-stimulated AC activity gradually declined to a relatively stable value that was maintained throughout the remainder of gestation, except for two transient increases in activity on days 14 and 19 of pregnancy. With parturition, luteal epinephrine-stimulated AC activity fell to basal levels. In corpora lutea of pseudopregnancy, epinephrine-stimulated AC activity was very similar to that of corpora lutea of pregnancy during the first 16 days but fell to basal levels on day 17 with the termination of pseudopregnancy. Neither corpora albicans nor interstitial tissue exhibited any epinephrine-stimulated AC activity. The presence of epinephrine-stimulated AC activity only in corpora lutea of pseudopregnancy and pregnancy and not in preovulatory Graafian follicles, corpora albicans, or interstitial tissue suggests a functional to role for catecholamines in luteal tissue. Moreover, these data indicate that the presence of an epinephrine-sensitive AC may be used as a functional marker for luteinization, at least in rabbit ovarian tissues.

Bioassay methods for relaxin: uses and pitfalls.

The ability of aqueous extracts of porcine corpora lutea of pregnancy to “relax” the pubic symphysis of the estrogen-primed ovariectomized guinea pig was first described by Hisaw (1926). Subsequent work showed that porcine luteal extracts which contained guinea pig pubic symphysis-relaxing activity could inhibit contractions of uterine myometrium of rats in vitro (Sawyer et al. 1953) and guinea pigs in vivo (Krantz et al.3 1950). Around the same time, it was reported that crude extracts of sow corpora lutea induced interpubic ligament formation in estrogen primed mice (Hall and Newton, 1946; Kliman et al. 3 1953). These basic observations led to the development of numerous bioassay methods for relaxin which have been amply documented in previous reviews (Frieden and Hisaw, 1953; Hall, 1960; Steinetz et al. 1969). The present paper will, therefore, be devoted primarily to a discussion of the uses (and abuses!) of the various assay methods, the pitfalls which may be encountered in assaying relaxin activity in impure extracts and the growing realization that relaxin activity may be associated with a family of related polypeptides. Of special interest are recent observations which suggest that relaxin-like hormones obtained from different species may not be equally effective in the classical bioassay methods.

Relaxin--a review.

Relaxin is a polypeptide hormone, similar in structure to insulin and has been found in the female of all species studied. The corpus luteum of pregnancy is the main source of relaxin in many species but in others the decidua is apparently of greater importance. It has also been found in other tissues; e.g. prostatic fluid, testis and ovary. First discovered and extracted from the corpora lutea of pregnant sows in an impure form in 1926, it was found to relax the pubic ligament of the oestrogen primed guinea-pig. It was named after this action, but has since been found to have many other possible roles, including preparation of the endometrium for implantation, inhibition of uterine activity in early pregnancy, remodelling of the uterine stroma during pregnancy, cervical ripening and the initiation of parturition. Relaxin's main cellular action in pregnancy may be to drive collagen biosynthesis in its target organs, thus facilitating the remodelling of the connective tissue. Due to the impurity of relaxin preparations used in clinical trials until the mid-1970's, the role of relaxin in the human has been in doubt. Porcine and rat relaxins have now been highly purified and their detailed structure is known. Human relaxin awaits adequate isolation, purification and characterization, and is not yet available for laboratory and clinical trials. However, the recent preparation of purified porcine relaxin for clinical trials and the availability of specific radioimmunoassays for this relaxin together with the identification of relaxin receptor sites, are rapidly helping to establish the concept that relaxin is indeed an important hormone both in human reproduction and in other physiological processes.

The consequences of infection of cattle with Akabane virus at the time of insemination

Viraemia was produced in 15 of 16 cows inoculated with Akabane virus into the uterus at oestrus and in 6 of 7 cows after intravenous inoculation. The route of inoculation did not alter the time of appearance, duration or titre of the viraemia. Four of the 10 cows inoculated after being artificially inseminated conceived and had uneventful pregnancies. At parturition the calves were normal and there was no Akabane virus or neutralizing antibody in their precolostral blood. In a sequential study from 3 to 10 days after inoculation of Akabane virus at oestrus, the reproductive tract and other tissues of 6 cows infected by intrauterine inoculation after artificial insemination were compared with those of 7 cows receiving virus intravenously after natural service. In both groups the corpus luteum was the only tissue to show histopathological changes. The effects of lesions on the early corpus luteum of pregnancy are discussed with reference to the reported high incidence of abortions and dead foetuses in epizootics due to Akabane virus.

Effect of bromocryptine on 20 alpha-hydroxysteroiddehydrogenase regulation in the corpus luteum of the pregnant rat.

Pregnant Sprague Dawley rats were passively immunized with antiserum to bovine luteinizing hormone (anti-LH) on day 10 of pregnancy, and treated with 1 mg/day or 1.5 mg/day of the prolactin (Prl) inhibitor bromocryptine (BEC) between days 10 to 12 or 9 to 12, respectively. On day 12 a laparotomy was performed to assess the state of pregnancy and to remove the ovaries for histochemical detection of 20 alpha-hydroxysteroiddehydrogenase (20 alpha-OHSD) in the corpora lutea of pregnancy. In a second experiment pregnant rats were treated with 1.5 mg BEC/day from days 17 to 22, checked for foetal state and ovariectomized on day 22 before giving birth. Treatment with BEC in effective doses did not interfere with anti-LH-induced termination of pregnancy and consequent reappearance of 20 alpha-OHSD activity on day 12, or with spontaneous recurrence of enzyme activity at the end of gestation. It is concluded that Prl has no direct and immediate role in 20 alpha-OHSD regulation, at least on day 12, although substitution by endogenous rat placental lactogen at the end of pregnancy cannot be excluded.

The Function of the Corpus Luteum of Pregnancy in Ovulatory Dysfunction and Luteal Phase Deficiency

Relatively little knowledge exists of corpus luteum function in early pregnancy after the successful treatment of ovulatory dysfunction or luteal phase deficiency. To assess the activity of the corpus luteum of such patients, human chorionic gonadotropin (hCG) and 17-hydroxyprogesterone (17-OH-P) levels were determined in serum samples obtained from normal women (44 patients), women with ovulatory dysfunction (10 patients), and women with luteal phase deficiency (7 patients); all determinations were made during conceptive cycles, and sampling continued into the first trimester of pregnancy. There were no statistically significant abnormalities of hCG levels when infertility patients were compared with control patients. According to the premise that 17-OH-P levels reflect corpus luteal function, there appeared to be adequate function in pregnancies after progesterone treatment of luteal phase deficiency. In pregnancies following ovulation induction with clomiphene, the corpus luteum function, on the basis of 17-OH-P levels, was significantly increased in magnitude and duration. These results have clinical implications with regard to supplemental hormone therapy in early pregnancy.

The role of the corpus luteum of lactation in the bandicoot Isoodon macrourus (Marsupialia: Peramelidae)

The concentration of progesterone in the plasma of the bandicoot was determined during pregnancy, during lactation, following removal of the young, and following surgical removal of the corpora lutea of lactation alone or along with the removal of the young. The corpus luteum of pregnancy continued into lactation and secreted progesterone for the first 19 days of lactation. In the later stages of lactation, the corpus luteum, which persisted morphologically until Day 45, was not secretory. Ovulation occurred approximately 20 days after the removal of the pouch young early in lactation. However after removal of both young and corpora lutea ovulation occurred in approximately 10 days. Thus early in lactation, when it is secreting progesterone, the corpus luteum may exert an additional ovulation inhibitory effect over and above that provided by suckling, but at later stages of lactation it is the suckling stimulus which is all important in inhibiting ovulation.

Effects of (15S)-15-methyl prostaglandin F 2 α methyl ester and estrogens upon the corpus luteum and conceptus of the rhesus monkey

The corpus luteum inhibiting activity of (15S)-15-methyl prostaglandin F 2 α methyl ester (15M-PGF 2 α ) was determined when given in combination with estrogens. Administration of 15M-PGF 2 α alone (3 injections of 500 μg each) to monkeys concomitantly receiving hCG reduced serum progesterone concentrations to 50% of values observed in control animals. Ethinyl estradiol or mestranol alone did not inhibit the corpus luteum of the hCG-treated, nonpregnant monkey. Serum progesterone values for nonpregnant monkeys treated with 15M-PGF 2 α plus estradiol-17β, ethinyl estradiol or mestranol did not differ statistically from those observed in monkeys treated with 15M-PGF 2 α alone. The dose of 15M-PGF 2 α (3 × 5 μg) which only partially inhibited the corpus luteum of the hCG-treated, nonpregnant monkey promptly terminated gestation when given on Day 28 of fertile menstrual cycles. Pregnancy terminated in two of three treated monkeys when the dose of 15M-PGF 2 α was reduced ten-fold (3 × 50 μg). Mestranol alone reduced serum progesterone and estradiol-17β concentrations to one-half and one-third of pretreatment values, but did not interrupt pregnancy. Pregnancy terminated in only two of five monkeys when mestranol was administered with the low dose of 15M-PGF 2 α . It is concluded that: 1) estrogens do not enhance the corpus luteum inhibiting activity of 15M-PGF 2 α in the nonpregnant monkey; 2) the primary action of 15M-PGF 2 α during early pregnancy is upon the conceptus and not the corpus luteum; 3) concomitant treatment with mestranol and 15M-PGF 2 α offers no advantage of 15M-PGF 2 α alone for the termination of early pregnancy; and 4) mestranol alone can impair the steroidogenic potential of the corpus luteum of early pregnancy, but is not sufficiently active to terminate gestation.