Alterations in uterine and placental prostaglandin F and E with gestational age in the rat

Experiments were designed to determine the chronological alterations in placental and uterine prostaglandin F and E (PGF and PGE) during pregnancy in the rat. Pregnant rats (sperm in the vagina = day 0) were sacrified at days 15, 18,19, 20, 21 and delivery (day 21 ) and placental and uterine tissues assayed (RIA) for PGF and PGE immediately (“ ”) or after 1 hour incubation (“ ”). Uterine content of PGF and PGE (ng PG/mg DNA) was increased significantly by day 19 and further increases were seen through delivery. Incubation of uterine tissue resulted in enhanced net production of PGF and PGE (p <.05) per mg DNA (as judged by tissue content and release into the incubation medium) by day 18 of pregnancy vs. day 15. Net production peaked around the time of delivery thus paralleling the alterations in tissue content .By contrast, no differences with gestational age were found in placental content of PGF and PGE , the concentrations throughout late gestation remaining in the range of uterine PGs at day 15. However, production of PGs per mg placental DNA increased markedly during incubation with significant enhancement detected by day 19 vs. 15, achieving levels even greater than the uterus .The and findings for the uterus are consistent with the hypothesis that increases in uterine PGs levels at the end of pregnancy may play an important role in parturition. The experiences with placental tissue suggest that the potential for PG production per placental cell may also increase in late gestation and thereby contribute to the augmented intrauterine availability of PGs at that time.     

Increase in uterine prostaglandin E2, F2 alpha, prostacyclin and stability in thromboxane A2 production during late pregnancy in streptozotocin-induced diabetic rats

This experiment was conducted to determine the effect of diabetes on uterine prostanoids production in near-term rats. The incidence of an insulin therapy was also studied. On the 21st day of pregnancy, uterine PGE2, PGF2 alpha and PGI2 levels showed a significant increase (respectively p less than 0.05, p less than 0.01 and p less than 0.05) in diabetic rats compared to controls whereas TxA2 production remained unchanged. The insulin therapy restored PGE2 levels, the most potent stimulatory factor of the myometrial fiber at control values, whereas it enhanced significantly PGI2 concentrations (p less than 0.05) and had no effect on PGF2 alpha production; TxA2 levels remaining always unchanged. It is suggested that the increase in uterine protanolds production during diabetes could induce a myometrial hypertonicity and play a role in the disturbances of the fetal development. The maintenance of PGE2 levels to control values by the insulin therapy might contribute to a normal delivery.     

Inhibition of prostaglandin synthesis and contractility in the rabbit and rat uterus by ibuprofen

Sixty uterine strips were excised from 8 pregnant and 7 post partum rabbits andstimulated electrically in vitro until they developed maximum isometric tension. The non-steroidal anti-inflammatory agent, Ibuprofen, at concentrations of 125, 250 and 500 μg/ml, signidicantly reduced tension of the 55 experimental uteri (P<0.001) within 7.5 minutes, in comaparison with the pretreatment value. Tension in 15 solvent-treated controls remained stable during the same observation period. The reduction in tension was greater in the post partum than the pregnant uteri (P<0.05). Sixteen additional uterine strips, excised from 4 preganant and 4 post partum rabbits were treated either with 500 μg Ibuprofen or solvent for 7.5 minutes. Radioimmunoassay showed that Ibuprofen significantly reduced the uterine levels of PGE (P<0.001) and PGE (P<0.001 post partum; P<0.05 pregnant) and again the effect was greater in the post partum unteri. These findings suggest that the suppression of uterine function by Ibuprofen is mediated by inhibition of PG-synthesis.In a subsequent study, 36 rats were treated with Ibuprofen on days 20 and 21 of pregnancy, at the ineffective dose level of 4 mg/day and the effective levels of 12, 20 and 30 mg/day, In comparison with the first group. Spontaneous labor was significantly delayed in the other three groups (P<0.05, P<0.01 and P<0.001, respectively). In addition, 7 rats were treated with 30 mg/day Ibuprofen and 7 with solvent on days 19 and 20 of pregnancy. In day 21, the Ibuprofen-treated rats showed a significant (P<0.001) reduction in the uterine PGF and PGE concentrations, indicating that the prolongation of pregnancy is mediated by an inhibition of uterine PG-synthesis.     

In vitro effects of progesterone and estradiol on uterine prostaglandin production in the pregnant rat.

Uterine prostaglandin (PG) levels increase markedly at the end of pregnancy in the rat and steroid hormones appear to be important regulators of this augmentation. The purpose of the present study was to examine the in vitro effects of progesterone (P) and estradiol (E2) on uterine PGE and PGF production in the pregnant rat. Uterine tissue was removed at Days 19 and 21 of pregnancy and incubated with P or E2 (0.1, 1, 10, 100, and 1,000 ng/ml) for 48 h in Ham's F-10 medium at 37 degrees C. P significantly (p less than 0.05) inhibited PGE and PGF production in a dose-dependent manner at Day 19, but not at Day 21 of pregnancy. In contrast, E2 had no effect (p greater than 0.05) at either day of pregnancy. In a second study, P was found to inhibit uterine PGE production at Days 15 and 19, but not at Day 21 or at delivery. A third study determined that the levels of P were greatly reduced in media containing uterine tissue from delivery when compared to media containing tissue from day 15 of pregnancy (p less than 0.05). In a fourth experiment, no difference in tritium-labeled P uptake was detected between media containing uterine tissue from Day 15 of pregnancy and media containing uterine tissue removed at delivery. This observation in association with data from the literature suggests that the disappearance of P from the media in experiment 3 might be due to enhanced P metabolism rather than to differential uptake of P by the tissue.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endocrine regulation of the onset of parturition in rats

The endocrine regulation of parturition exhibits several interspecies differences. Among the endocrine parameters considered to be the most important ones from the point of view of the regulation of parturition the concentration of oestrogens (oestradiol, oestriol and oestrone), progesterone, PGF2 alfa and its degradation product PGFM, was determined in both peripheral and uterine venous blood by RIA method in rats starting from the 15th day of pregnancy to the 3rd or 4th day following parturition. In the pregnant rat oestriol could only be detected on the day of parturition (21th day). Concentrations of oestriol and oestradiol were the highest on the day of parturition. An opposite tendency could be observed as far as progesterone concentration was concerned, i.e., the concentration decreased gradually from the 15th day of pregnancy onwards and the lowest value was reached on the day of parturition both in peripheral and uterine venous blood. PGF2 alfa and PGFM concentrations in the uterine vein increased gradually from the 15th day of pregnancy and the highest value could be detected peri partum. Our data, in accordance with those of others support the idea that the hormones investigated are involved in the process of parturition, i.e., characteristic changes of oestrogens, progesterone and prostaglandin levels ensue in the rat prior to parturition.     

Prostaglandins E and F in uterine venous plasma in relation to peripheral plasma levels of progesterone and 20α-hydroxyprogesterone in the rat throughout pregnancy and parturition

Prostaglandins E and F in uterine venous plasma and progesterone (P) and 20α-hydroxyprogesterone (20α-OH-P) in peripheral plasma were measured by radioimmunoassays throughout pregnancy and parturition in the rat. E Prostaglandins are low (approx. 2 ng/ml) and maintain a more or less constant level throughout most of the pregnancy except just before parturition when they rise to 3.8 ng/ml on day 20. F Prostaglandin levels are always higher than E prostaglandins and show distinct peaks around day 5 (5 ng/ml), day 11 (7 ng/ml), and before parturition (8.4 ng/ml).Progesterone levels are higher than 20α-OH-P levels throughout most of the pregnancy (day 6–20); however, during early pregnancy (day 1–5) and before parturition more 20α-OH-P than P is present in peripheral blood.The possible role of uterine venous prostaglandin levels in altering the 20α-OH-P/P ratio during pregnancy and parturition is discussed.     

Androgen receptor in the reproductive systems of pregnant pigs and rats

The immunohistochemical expression of the androgen receptor (AR) was investigated in the ovarian atretic follicles and corpora lutea (CL) of pregnant pigs and rats, as well as in porcine uteri and fetuses. Follicular atresia involved either abnormal persistence or depletion of AR in various follicular compartments. Porcine and rat CL expressed nuclear AR. However, in the porcine CL, starting from day 70 of pregnancy, mainly cytoplasmic staining was observed, with exclusively cytoplasmic expression found on day 90. In the CL of pregnant rats, differences in AR distribution within the same CL were observed and decreasing AR expression during luteal regression was found. AR mRNA and protein expression in the porcine uterus depended on the uterine compartment and the day of pregnancy. AR-positive were also testes, ovaries, uteri, kidneys and lungs of fetuses.     

Intraperitoneal infusion of proinflammatory cytokines does not cause activation of the rat uterus during late gestation

Increased concentrations of IL-1beta and TNF-alpha have been associated with parturition. However, the role of these cytokines is unknown. Before parturition, the uterus undergoes a process of activation, during which there are significant changes in expression of genes associated with increased uterine contractility, including the receptors for oxytocin (OT) and prostaglandin (PG)F(2alpha) (FP), PGH(2) synthase isoform 2 (PGHS2), the gap junction protein connexin-43 (Cx-43), and the inducible isoform of nitric oxide synthase (iNOS). To determine whether IL-1beta or TNF-alpha was part of the causal mechanism for increased uterine contractions, we placed osmotic pumps infusing IL-1beta or TNF-alpha into the peritoneal cavity of late pregnant rats (gestation day 19) and measured the effects on uterine contractility and on the uterine concentrations of mRNA for the contraction-associated genes 24 h later. Maternal serum concentrations of IL-1beta and TNF-alpha were increased significantly. By day 21, the control animals had significant increases (P < or = 0.05) in mRNA for OT, FP, PGHS2, and Cx-43, a decrease (P < or = 0.05) in iNOS, and an increase (P < or = 0.05) in uterine sensitivity and responsiveness to OT. Infusion of IL-1beta or TNF-alpha had no effect on uterine contractility or on expression of the activation-associated genes. We conclude that intraperitoneal infusion of IL-1beta or TNF-alpha resulting in significantly increased maternal serum cytokine levels does not cause uterine activation. The role of proinflammatory cytokines in the mechanism of parturition remains unclear.     

Bacterial contamination of the uterus after parturition and its effect on the reproductive performance of cows on large-scale dairy farms

The bacteriological status of the uteri of 150 cows was examined on 14 large-scale dairy farms 10 to 20 d after parturition and then twice again in 2-wk intervals during uterine involution. The degree of bacterial contamination and the proportion of the infected uterus as well as the composition of the isolated flora were determined. The antibiotic sensitivity of the important bacterium strains was also studied. The relationship between the reproductive data and bacterial contamination of the uteri was analyzed, and the influence of certain environmental and genetic factors on the rate of infection was examined. The proportion of cows having moderate or more serious uterine infection remained above 30 % at the end of involution on more than 35 % of the farms. Infections were caused mainly by streptococci, E. coli and corynebacteria. The bacterium strains showed broad resistance against commericially available antibiotics. There were significant differences in the length of time from the parturition to the first insemination and conception among cows at the various farms. There was a significant correlation between these differences and the bacteriological status of the uteri. Reproductive data were the lowest in the group of cows infected with Corynebacterium pyogenes. The rate of the infected uteri was considerably higher after the third parturition and in cows producing less than 20 l of milk per day. No connection was found between the bacteriological status of the uteri and the breed, type of housing, and season of the parturitions.     

Relationships between histological signs of atresia, steroids in follicular fluid, and gonadotropin binding in individual bovine antral follicles during postpartum anovulation

Two experiments were conducted to determine the relationship between histological signs of atresia, gonadotropin binding, and steroids in fluid of medium-sized bovine follicles during postpartum anestrus. In Experiment I, ovaries of 21 cows were removed on Days 7, 14, 28, 42, or 56 after parturition. In Experiment II, ovaries of 29 cows were removed between Days 20 and 30 postpartum after 48 or 96 h of either saline (0.9% NaCl, 5 ml) or luteinizing hormone-releasing hormone (LHRH; 500 ng/5 ml saline) injections given every 2 h via jugular cannulas. Two to 10 follicles, 4.0-7.9 mm in diameter, were removed per pair of ovaries. Follicles were classified as normal, intermediate, atretic, or luteinized-atretic, depending on their micromorphology. In both Experiments I and II, follicles classified as normal had 50-80% lower (p less than 0.05) concentrations of progesterone and 2- to 7-fold greater (p less than 0.05) concentrations of estradiol than atretic follicles. However, concentrations of androstenedione and gonadotropin-binding sites were similar in normal and atretic follicles. Atretic follicles had degenerative granulosa with several pyknotic nuclei, thick theca, and little distinction between theca and granulosa. Intermediate follicles showed slight signs of degeneration and had 2- to 3-fold greater (p less than 0.05) concentrations of progesterone than normal follicles. Concentrations of estradiol did not differ (p greater than 0.10) between normal and intermediate follicles. Equal proportions of normal and atretic medium-sized follicles were located on the ovaries bearing the corpus albicans from pregnancy (CAP).(ABSTRACT TRUNCATED AT 250 WORDS)     

Uterine lymphocyte distribution and interleukin expression during early pregnancy in cows

Both the production of cytokines and the distribution of immune cells within the uterus change during early pregnancy. Evidence obtained mainly from mice indicates that these changes are important for implantation and in preventing a maternal immune response to the conceptus. The ruminant embryo also produces interferon tau at this time, the signal for the maternal recognition of pregnancy. The relationship between these events in cows was studied using uteri from three groups of animals on day 16 after observed oestrus: (i) cyclic controls, (ii) pregnant and (iii) inseminated but with no embryo present. Embryo size and the antiviral activity in uterine flushings (indicative of the interferon tau concentration) were measured. Sections of intact uterus were frozen for the localization and quantitation of CD4(+) (T lymphocytes), CD14(+) (macrophages) and CD21(+) (B lymphocytes) uterine cells by immunohistochemistry. The expression of interleukin (IL)-1alpha, IL-2, IL-6 and IL-10 mRNAs in uterine extracts was measured by RT-PCR. Neither embryo size, interferon tau concentration nor pregnancy status influenced the distribution of CD4(+), CD14(+) or CD21(+) cells in the day 16 uterus. Endometrial IL-1alpha mRNA was detected in most cows across the groups, whereas IL-2 mRNA was only present in the non-pregnant uterus. IL-6 and IL-10 mRNAs were not detectable in any uteri. In conclusion, IL-2 mRNA expression is detectable in the non-pregnant but not the pregnant uterus on day 16 and interferon t is unlikely to play a role in the redistribution of immune cells in the uterus during early bovine pregnancy.     

Effect of dietary restriction on triglyceride levels in the uterus isolated from pregnant rats. Influences of prostaglandins and indomethacin

Triglyceride (TGs) concentrations in uterine strips isolated from 14 or from 21 days-pregnant rats, either normal-fed or following a restricted-diet rats (50% food intake for 14 days), were measured. Determinations were made immediately after killing (0 min time or post-isolation) as well as after a period of incubation in glucose-free medium (60 min time or post-incubation). The post-isolation levels of TGs (0 min) in the uterus from normal-fed animals at 14 or at 21 days of pregnancy, were significantly higher in implantation sites than in the interembryonic segments. These values of TGs (0 time) did not change, in comparison to post-incubation concentrations (60 min), either without additions or in the presence of indomethacin (5 X 10(-6) M) or of prostaglandins (PGs) E1, E2 or F2 alpha (10(-7) M). At 0 time, uterine TGs of rats subjected to dietary restriction, increased as pregnancy progressed, more than in normal-fed controls. The post-incubation (60 min) pattern was different depending on the days of pregnancy; i.e. at 14 days, incubation in Krebs-Ringer Bicarbonate-medium (KRB) led to a significant fall unaffected by the addition of propranolol (10(-6) M). However, in the presence of indomethacin, TGs values had a level similar to the initial one (0 time). Furthermore, exogenous PGE1 or PGE2 failed to alter the effect of indomethacin, as PGF2 alpha did.(ABSTRACT TRUNCATED AT 250 WORDS)     

Progesterone and oestrogen receptors in the female genital tract throughout pregnancy in tammar wallabies

The tammar, Macropus eugenii, is a monovular macropodid marsupial which has a post-partum oestrus and an 11 month embryonic diapause. Progesterone and oestradiol cytosol receptors were measured by Scatchard analyses and single point analysis in the lateral vagina, endometrium and myometrium of the gravid and contralateral non-gravid uterus throughout pregnancy, immediately after parturition and during seasonal reproductive quiescence. In endometrial tissues, both progesterone and oestradiol receptors doubled in concentration in both gravid and non-gravid uteri between day 0 and day 5 of pregnancy, coinciding with previously described peak values in peripheral plasma progesterone and oestrogen. Receptor concentrations in endometrial tissue during seasonal quiescence were not significantly different from those immediately after reactivation. After day 12 of pregnancy, downregulation of both progesterone and oestradiol cytosolic receptors occurred concomitant with the increase in progesterone in the peripheral plasma. However, there was a unilateral increase in oestradiol receptor concentrations in endometrium obtained from the non-gravid uterus between day 25 of the 26.5 day gestation and immediately after parturition. Myometrial receptor concentrations mirrored those of the endometrium but were lower. Concentrations of progesterone receptor in the lateral vaginae were at the lower limit of detection, while the oestradiol cytosol receptor concentrations were even lower in this tissue. Thus, the steroid receptor concentrations provide another example of local unilateral endocrine responses in the reproductive tract of the tammar. These results also indicate that the downregulation of progesterone and oestradiol receptors that occurs in both uteri in mid- and late-pregnancy is selectively and locally reversed before parturition in the non-gravid endometrium in response to the local effects of follicular oestradiol from the ipsilateral ovary.     

Metabolism of testosterone in vivo in the pregnant rat

The metabolism of testosterone (T) was examined during the second half of pregnancy in the rat to determine whether utilization of T for estradiol (E2) synthesis occurs via conversion of T to androstenedione (A). On Days 11, 16, and 21 of gestation (term = Day 23), rats (n = 7-9/group) were anesthetized and a constant infusion of [3H]T was initiated. At 60 min, blood was obtained from a jugular vein and the ovaries (Days 11, 16, and 21), and placentae and uterine tissue (Day 16 only) were removed. In a second study performed in rats on Day 16 of gestation (n = 8-10/group), the ovaries and/or gravid uterus were removed 15 min after initiation of [3H]T infusion, and blood was taken from a jugular vein 60 min later. Radiolabeled T and A were purified from serum and tissues by paper chromatography. In a third group of rats (n = 6), jugular vein samples were obtained sequentially on Days 11, 16 and 21 of gestation and serum concentrations of T were measured by radioimmunoassay. The metabolic clearance rate of T was constant during the study period (overall mean = 31 1/day). In contrast, the serum concentration of T (pg/ml) on Day 16 of gestation (863 +/- 108) exceeded (p less than 0.02) that on Day 11 (445 +/- 74); the latter was similar to that measured on Day 21 (592 +/- 109). Thus, the estimated production rate of T was greatest on Day 16 of gestation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Uterotropic action of indomethacin on the rat uterus

Administration of indomethacin (10 mg/kg body weight, twice daily for 6 days) resulted in a significant (P less than 0.01) increase in the weight, and cross-sectional area of uteri of ovariectomized rats, whereas no such effects were observed following indomethacin administration to normal cycling rats. Prostaglandin F2 alpha (PGF2 alpha) content (ng/uterus) and concentration (ng/g wet weight) in the uterus of indomethacin-treated animals were reduced 40.4% and 60.8%. Simultaneous administration of either estradiol-17 beta (E2), progesterone testosterone with indomethacin to ovariectomized rats failed to reduce the uterine weight increase. On the contrary, concomitant administration of E2 (25 or 100 ng/day) and indomethacin resulted in uterine weight increases which were greater than those associated with indomethacin alone. Uterine E2 content was significantly higher in animals treated with indomethacin plus E2 as compared to those given estradiol alone. Uterine uptake of 2,4,6,7-[3H]E2 following i.v. administration was greater in animals pretreated with indomethacin (5 mg/kg, twice daily) for 3 days than in ovariectomized controls. These results suggest that prostaglandins may be involved in the regulation of uterine growth.     

Dihydrotestosterone secretion in pregnant and pseudopregnant rats

The objective of this study was to determine levels of dihydrotestosterone in the peripheral circulation and the source of its secretion throughout pregnancy and pseudopregnancy. Rats were bled from the jugular vein and ovarian or uterine vein from Day 8 through Day 22 of pregnancy and from Day 8 through the end of pseudopregnancy in various types of pseudopregnant rats. Jugular vein samples alone were obtained on the day of parturition and every fourth day thereafter during the lactational period. Our results indicate that the levels of dihydrotestosterone in the peripheral circulation were high throughout pregnancy and pseudopregnancy then declined during the lactational period. The sources of dihydrotestosterone were primarily the ovary in pseudopregnant rats and the ovary plus uterus in pregnant rats.     

The effect of postbreeding uterine lavage on pregnancy rate in mares

One stallion and 54 mares were used in an experiment to evaluate the effect of postbreeding uterine lavage on pregnancy rate in mares. All mares were inseminated with 250 x 10(6) progressively motile sperm every other day during estrus until detection of ovulation. Mares (n = 18) were randomly assigned to one of three treatment groups: 1) no postbreeding uterine lavage (control); 2) uterine lavage at 0.5 h postbreeding; or 3) uterine lavage at 2 h postbreeding. A dilute solution of povidone-iodine (PIS; 0.05%) previously determined to render spermatozoa immotile in vitro was used to lavage the mare uteri. One liter PIS, prewarmed to 40 degrees C, was used for each lavage. Pregnancy status of mares was determined at 21 d and 36 d post ovulation, using transrectal ultrasonography. The pregnancy rate of Group 1 (66.7%) was higher than that of Group 2 (22.2%; P<0.05) or Group 3 (33.3%); P<0.10). The pregnancy rates of Groups 2 and 3 were similar (P>0.70). Evaluation of endometrial biopsies obtained from a separate set of mares (n = 3) on Day 6 post ovulation, both before and after uterine lavage, revealed no difference in the accumulation of inflammatory cells, suggesting adverse effects of lavage on fertility may have been due to excessive removal of spermatozoa from the uterus during the lavage process or damage to oviductal spermatozoa.     

Increase in urinary thromboxane excretion during pregnancy and labor

Urinary TXB2 excretion was measured during pregnancy and labor using high pressure liquid chromatography and radioimmunoassay. From the first trimester onwards TXB2 levels in urine of pregnant women (n = 60) were significantly (p less than 0.001) higher than in non-pregnant women (n = 12) and they increased, albeit not significantly, with advancing gestation. Labor was associated with a two-fold increase in urinary TXB2 excretion. Levels in established labor were significantly higher than at any other time in pregnancy (p less than 0.001), but the levels in incipient labor showed considerable overlap with these in late pregnancy. Thus urinary TXB2, while not necessarily originating from the pregnant uterus, appears to reflect the uterine activity of labor and may be the expression of a general stimulation of prostanoid production during parturition.     

Probable influence of ova and embryo prostaglandins in the differential ovum transport in pregnant and cycling rats.

In this study we explored the possible underlying mechanism(s) of the differential transport of unfertilized and fertilized ova in cycling and pregnant rats. The number of ova recovered from rat oviducts and uterus was not significantly different in estrus, metestrus and diestrus but dropped sharply at proestrus. When estrus rats were injected with indomethacin (10(-6)), a well known inhibitor of cyclooxygenase, delivered into both ovarian bursae, and sacrificed next day at metestrus, the number of ova in the oviduct was significantly smaller (p less than 0.025) than in controls at metestrus. On the other hand, when diestrus rats were injected with PGE1 (10(-6)) delivered into both ovarian bursae, and sacrificed next day at proestrus, no ova were found in the oviducts, and only a few of them were in the uterus. When fertilized ova were recovered from oviducts and uteri at day 4 of pregnancy (corresponding to proestrus of cycling rats) an average of 4 embryos were still found in the oviducts, proving a differential ovum transport between cycling and pregnant rats. In order to establish if there exists any ova or embryo releasing factor responsible for this difference, the prostaglandins released to the incubation medium by ovum or 3-day embryo were measured. Unfertilized ova produced significantly more PGE1 (p less than 0.05) than PGE2 or PGF2 alpha. The same pattern of PG production was observed with incubated embryos, but in this case the amount of PGE1 released was significantly higher (p less than 0.01) that the PGE1 released by unfertilized ova.(ABSTRACT TRUNCATED AT 250 WORDS)