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.     

A note on the absence of acth-like activity secreted by the goat placenta in vivo and on the independence of fetal endocrine development of the maternal hypophysis

In the goat, maternal hypophysectomy on Day 60 of gestation or treatment with 5 mg bromocriptine/day between Days 60 and 120 of gestation did not affect fetal body weights or the weights of the fetal adrenals, thyroid, pituitary gland or gonads when examined at 120 days gestation. The maternal adrenal cortex regressed after hypophysectomy of the pregnant goat.     

Studies on prostaglandin metabolism in corpora lutea of rabbits during pregnancy and pseudopregnancy

Corpora lutea and ovarian stromal tissue were analysed for prostaglandin (PG) concentrations and activities of enzymes involved in PG metabolism at 8, 10, 12, 13 and 15 days after induction of ovulation. In CL of pseudopregnant rabbits, the PGE-2-9-ketoreductase (PGE-2-9-KR) was highly active on Days 10, 12 and 15 when compared with Day 8 (P less than 0.01; P less than 0.001; P less than 0.05). In pregnant animals PGE-2-9-KR activity was only increased on Day 12 (P less than 0.05) but declined to basal levels on Days 13 and 15. Comparing PGE-2-9-KR activity of pseudopregnant and pregnant animals, a significant elevation was found on Day 15 of pseudopregnancy (P less than 0.025). Activities of PG-15-hydroxydehydrogenase did not exhibit any significant changes with time in pseudopregnant or pregnant rabbits. PGE-2 concentrations were increased on Days 12, 13 and 15 (P less than 0.025) when compared with Day 8. Changes in PGF-2 alpha concentrations paralleled those of PGE-2-9-KR. The concentrations of PG metabolites 13,14-dihydro-15-keto-PGE-2 and -PGF-2 alpha were lower than those of the primary PGs and did not show stage-specific changes in pseudopregnant and pregnant animals. These results demonstrate that the rabbit CL possesses enzymes to convert PGE-2 to PGF-2 alpha and to metabolize both PGs. PGE-2-9-KR may be involved in regulating the PGF-2 alpha/PGE-2 ratio and possibly in controlling the life-span of the corpus luteum.     

In vivo levels of prostaglandin F2 alpha, E2 and prostacyclin in the corpus luteum of pregnant and pseudopregnant rats

Prostaglandin F2 alpha (PGF2 alpha) is a well-known luteolytic factor in the rat corpus luteum. To investigate a possible luteal origin of PGF2 alpha, measurements of this prostaglandin were performed in different luteal tissues in vivo. Prostaglandin E2 (PGE2) and the stable metabolite of prostacyclin, 6-keto-PGF1 alpha, were assayed simultaneously. Corpora lutea of different ages from 57 pregnant and pseudopregnant rats (mated with sterile males) were rapidly excised, dissected in 0 degree C indomethacin solution, homogenized, and extracted for prostaglandins with solid-phase extraction cartridges. Prostaglandins were determined by radioimmunoassay. Plasma levels of progesterone and 20 alpha-dihydroprogesterone were also monitored. In the adult pseudopregnant rat model, luteolysis occurs at Day 13 +/- 1, and maximal levels of all three prostaglandins were detected on Day 13 of pseudopregnancy: 0.40 +/- 0.02, 2.6 +/- 0.29, and 1.76 +/- 0.24 pmol/mg protein (mean +/- SEM, n=7) for PGF2 alpha, PGE2, and 6-keto-PGF1 alpha respectively. In pregnant rats, on the corresponding day, levels were considerably lower: 0.15 +/- 0.02, 0.90 +/- 0.13, and 0.50 +/- 0.06 pmol/mg protein (mean +/- SEM, n=9, p less than 0.0001), respectively. Luteal levels in pregnant rats showed a continuous decline on Days 13 and 19 for all prostaglandins measured, whereas in pseudopregnant rats an increment of PGF2 alpha was noted between Days 7 and 13 and remained high on Day 19. PGE2 closely followed levels of PGF2 alpha, but at a 5- to 10-fold higher level. The coefficient of correlation between PGF2 alpha and PGE2 in the luteal compartment of both models was 0.87 (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of maternal stress on uranium-induced developmental toxicity in rats

It has been demonstrated that uranium is an embryo/fetal toxicant when given orally or subcutaneously to pregnant mice. On the other hand, maternal stress has been shown to enhance the developmental toxicity of a number of metals. In this study, maternal toxicity and developmental effects of a concurrent exposure to uranyl acetate dihydrate (UAD) and restraint stress were evaluated in rats. Four groups of pregnant animals were given subcutaneous injections of UAD at 0.415 and 0.830 mg/kg/day on Days 6 to 15 of gestation. Animals in two of these groups were also subjected to restraint for 2 hr/day during the same gestational days. Control groups included restrained and unrestrained pregnant rats not exposed to UAD. Cesarean sections were performed on gestation Day 20, and the fetuses were weighed and examined for malformations and variations. Maternal toxicity and embryotoxicity were noted at 0.830 mg/kg/day of UAD, while fetotoxicity was evidenced at 0.415 and 0.830 mg/kg/day of UAD by significant reductions in fetal body weight and increases in the total number of skeletally affected fetuses. No teratogenic effects were noted in any group. Maternal restraint enhanced uranium-induced embryo/fetal toxicity only at 0.830 mg/kg/day, a dose that was also significantly toxic to the dams. As in previous studies with other metals, maternal stress enhances uranium-induced developmental toxicity at uranium doses that are highly toxic to the dams; however, at doses that are less acutely toxic the role of maternal stress would not be significant.     

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.     

Effects of environmental stress or ACTH treatment during pregnancy on maternal and fetal plasma androstenedione in the rat

Prenatal stress applied during the last trimester of pregnancy has been shown to alter fetal development and influence adult sexual behavior. Since androstenedione (Δ⁴) has the potential to participate in differentiation processes, this study was designed to assess the effect of prenatal stress on maternal and fetal Δ⁴ titers. Restraint/illumination/heat (environmental stress) or ACTH injections were used to stress pregnant rat dams beginning on Day 14 of pregnancy. Blood samples and organ weights were obtained from nonpregnant animals, pregnant rats on Days 5, 10, 15, 18, and 20 of pregnancy, and fetuses on Days 18 and 20 of gestation. Maternal and male and female fetal Δ⁴ titers were determined by radioimmunoassay. ACTH and environmental stress significantly reduced fetal body weight and male anogenital distance. Environmental stress also significantly reduced the size of 20-day fetal adrenals and testes. Each treatment caused significant short-term (1 hr after treatment) and long-term (16 hr after treatment) elevation of maternal plasma Δ⁴ on Days 15 and 18 of gestation, but only short-term elevation of Δ⁴ titers on Day 20. ACTH treatment did not cause long-term elevation of fetal Δ⁴ although both ACTH treatment and environmental stress generated a significant short-term increase in fetal Δ⁴ titers. Environmental stress produced long-term elevation of fetal Δ⁴ in 18-day fetuses of both sexes and in 20-day female fetuses. It is concluded that maternal stress and exogenous ACTH significantly elevate maternal and fetal Δ⁴ titers during the prenatal period postulated to be critical in sexual differentiation of the rat brain.     

Progesterone and gravidity differentially regulate expression of extracellular matrix components in the pregnant rat myometrium

Myometrial growth and remodeling during pregnancy depends on increased synthesis of interstitial matrix proteins. We hypothesize that the presence of mechanical tension in a specific hormonal environment regulates the expression of extracellular matrix (ECM) components in the uterus. Myometrial tissue was collected from pregnant rats on Gestational Days 0, 12, 15, 17, 19, 21, 22, 23 (labor), and 1 day postpartum and ECM expression was analyzed by Northern blotting. Expression of fibronectin, laminin beta2, and collagen IV mRNA was low during early gestation but increased dramatically on Day 23 during labor. Expression of fibrillar collagens (type I and III) peaked Day 19 and decreased near term. In contrast, elastin mRNA remained elevated from midgestation onward. Injection of progesterone (P4) on Days 20-23 (to maintain elevated plasma P4 levels) delayed the onset of labor, caused dramatic reductions in the levels of fibronectin and laminin mRNA, and prevented the fall of collagen III mRNA levels on Day 23. Treatment of pregnant rats with the progesterone receptor antagonist RU486 on Day 19 induced preterm labor on Day 20 and a premature increase in mRNA levels of collagen IV, fibronectin, and laminin. Analysis of the uterine tissue from unilaterally pregnant rats revealed that most of the changes in ECM gene expression occurred specifically in the gravid horn. Our results show a decrease in expression of fibrillar collagens and a coordinated temporal increase in expression of components of the basement membrane near term associated with decreased P4 and increased mechanical tension. These ECM changes contribute to myometrial growth and remodeling during late pregnancy and the preparation for the synchronized contractions of labor.     

Steroid regulation of cell specific secreted phosphoprotein 1 (osteopontin) expression in the pregnant porcine uterus

Secreted phosphoprotein 1 (SPP1, commonly referred to as osteopontin and formerly known as bone sialoprotein 1, early T-lymphocyte activation 1) is an extracellular matrix/adhesion molecule that is upregulated in the pregnant uterus of all mammals examined to date. This study focused on the pig, which has true epitheliochorial placentation and exhibits induction of SPP1 mRNA in luminal epithelium (LE) just before conceptus attachment and in glandular epithelium (GE) after Day 30 of pregnancy. The objective of this study was to determine steroid regulation of SPP1 mRNA and protein in porcine uterine epithelium. To examine the effect of estrogen, cyclic gilts were treated daily (Days 11-14) with 5 mg estradiol benzoate (i.m.) and hysterectomized on Day 15. To evaluate the long-term effect of pseudopregnancy, cyclic gilts were given daily injections (Days 11-15) with steroid as above and hysterectomized on Day 90. In situ hybridization showed high expression of SPP1 mRNA only in LE contiguous with apposing conceptus tissue on Day 15 of pregnancy. In contrast, estrogen injection resulted in moderate but uniform SPP1 mRNA in all LE of Day 15 nonpregnant gilts, with expression maintained through Day 90 of pseudopregnancy. SPP1 mRNA also localized to the GE of Day 90 pseudopregnant gilts, similar to expression in late gestation. Consistent with in situ hybridization results, SPP1 protein localized to the apical surface of LE in all estrogen-treated gilts and in the GE on Day 90 of pseudopregnancy. We conclude that, in pregnant pigs, SPP1 is induced by conceptus estrogen in uterine LE and is regulated in GE in a manner coincident with CL/placental progesterone production.     

Placental growth, angiogenic gene expression, and vascular development in undernourished adolescent sheep

Limiting maternal nutrient intake during ovine adolescent pregnancy progressively depleted maternal body reserves, impaired fetal nutrient supply, and slowed fetal soft tissue growth. The present study examined placental growth, angiogenic gene expression, and vascular development in this undernourished adolescent model at Days 90 and 130 of gestation. Singleton pregnancies were established, and ewes were offered an optimal control (C; n = 14) or low (L [0.7 x C]; n = 21) dietary intake. Seven ewes receiving L intakes were switched to C intakes on Day 90 of gestation (L-C). Fetal body weight (P < 0.01) and glucose concentrations (P < 0.03) were reduced in L versus C pregnancies by Day 130, whereas L-C group values were intermediate. Placental cellular proliferation, gross morphology, and mass were independent of maternal nutrition at both Day 90 and 130. In contrast, capillary area density in the maternal caruncular portion of the placentome was reduced by 20% (P < 0.001) at both stages of gestation in L compared with C groups. Caruncular capillary area density was equivalent in the L and L-C groups at Day 130. Placental mRNA expression of five key angiogenic ligands or receptors increased (P < 0.001) between Days 90 and 130 of gestation. VEGFA mRNA expression was higher (P < 0.04) in L compared with C and L-C pregnancies at Day 130, but otherwise gene expression of the remaining angiogenic factors and receptors analyzed was unaffected by maternal intake. Undernourishing the pregnant adolescent dam restricts fetal growth independently of changes in placental mass. Alterations in maternal placental vascular development may, however, play a role in mediating the previously reported reduction in maternal and hence fetal nutrient supply.     

Effect of pregnancy and exogenous ovarian steroids on endometrial prolactin receptor ontogeny and uterine secretory response in pigs

During gestation, pigs have constant circulating levels of prolactin (PRL), and lack decidual PRL and placental lactogens. Effects of PRL on uterine physiology in pigs may be due to changes in endometrial PRL receptors. In this study, effects of the conceptus and cyclic hormonal environment on endometrial PRL receptors were investigated. Endometrial PRL receptor numbers were similar between Days 8 and 15 for cyclic gilts. In contrast, endometrial PRL receptor numbers for pregnant gilts were similar between Days 8 and 11, then increased (p less than 0.05) on Day 12 and remained elevated between Days 14 and 30. This day-by-status interaction approached significance (p less than 0.06) and overall receptor numbers were higher (p less than 0.01) for pregnant than for cyclic gilts. Pig conceptuses secrete estrogen between Days 11 and 12; therefore, regulation of endometrial PRL receptors by acute administration of estradiol was investigated. Uterine flushings and endometrium were collected from one uterine horn of cyclic gilts on Day 11; then, at 1, 6, 12, and 24 h following a single injection of estradiol valerate (EV; 5 mg, into adipose tissue), uterine flushings and endometrium were collected from the second uterine horn. Endometrial PRL receptor numbers were higher (p less than 0.05) at both 1 h and 6 h after treatment with EV and then decreased (p less than 0.02) by 12 h to below pretreatment values. In uterine flushings, total recoverable protein (p less than 0.05), uteroferrin (p less than 0.01), leucine aminopeptidase (p less than 0.05), calcium (p less than 0.03), sodium (p less than 0.01), and potassium (p less than 0.05) increased between 12 and 24 h following EV treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ontogeny of adenosine deaminase in the mouse decidua and placenta: immunolocalization and embryo transfer studies

This study has determined the cellular site of adenosine deaminase (ADA) expression in the mouse during development from Days 5 through 13 (day vaginal plug was found = Day 0) of gestation. Developmental expression of ADA progressed in two overlapping phases defined genetically (maternal vs. embryonal) and according to region (decidual vs. placental). In the first phase, ADA enzyme activity increased almost 200-fold in the antimesometrial region (decidua capsularis + giant trophoblast cells) from Days 6 through 9 of gestation but remained low in the mesometrial region. Immunohistochemical staining revealed a major localization of ADA to the secondary decidua. In the second phase, ADA activity increased several-fold in the placenta (labyrinth + basal zones) from Days 9 through 13 of gestation but remained low in the embryo proper. Immunohistochemical staining revealed a major localization of ADA to secondary giant cells, spongiotrophoblast, and labyrinthine trophoblast. Regression of decidua capsularis and growth of the spongiotrophoblast population accounted for an antimesometrial to placental shift in both ADA enzyme activity and a 40-kDa immunoreactive protein band. To verify a shift from maternal to fetal expression, studies were performed with two strains of mice (ICR, Eday) homozygous for a different ADA isozyme (ADA-A, ADA-B). Blastocysts homozygous for Adab were transferred to the uterus of pseudopregnant female recipients homozygous for Adaa. The isozymic pattern in chimeric embryo-decidual units analyzed at Days 7, 9, 11, and 13 revealed a predominance of maternal-encoded enzyme at Days 7 through 11 of gestation and a shift to fetal-encoded enzyme by Day 13. Thus, maternal expression of ADA in the antimesometrial decidua may play a role during establishment of the embryo in the uterine environment, whereas fetal expression of ADA in the trophoblast might be important to placentation.     

Trypanosoma lewisi and T. cruzi: Effect of infection on gestation in the rat

Termination of pregnancy occurred in the rat after infection with Trypanosoma lewisi early in gestation. Rats were inoculated on Day 2 of pregnancy and the uteri were excised and examined on Days 10 and 14 of gestation. There were no detectable differences in size in the fetuses of infected and control females at Day 10, but by Day 14 young of infected females were being reabsorbed, and their weight was markedly less than that of control young.A bioassay of estrogens and progestogens based on the decidual cell response indicated that there was a sufficient hormone level to maintain pregnancy beyond Day 10, so the mechanism of action by which fetal death was produced did not appear to be hormone depletion. The crucial changes in fetal weight occurred between Days 12 and 14 of gestation in rats infected with T. lewisi on Day 2 of gestation.Trypanosoma cruzi caused little or no pathologic change in the pregnant laboratory rat throghout the period of gestation and infected females gave birth to apparently normal young.     

Effect of decidual tissue on the uterine production of prostaglandins in pseudopregnant rats.

The concentration of prostaglandin F (PGF) in uterine vein plasma of non-traumatized pseudopregnant rats and pseudopregnant rats with deciduomata were not significantly different from each other at any of the times of pseudopregnancy studied (Days 7, 10 and 12). There was a significant increase in PGF levels on Day 10 in both groups of pseudopregnant animals (P less than 0-05) compared to the Day 4 values, and PGE values were significantly greater on Day 10 in the decidual tissue-bearing rats (P less than 0-01). A slight but not significant elevation in PGE concentration was observed on Days 7 and 12 in rats with deciduomata, but there was no significant difference in the control rats on Days 4, 7, 10 or 12. The results indicate that the prolongation of pseudopregnancy in rats with deciduomata is not due to a decreased production of uterine PGs and lend support to the recent suggestion of a luteotrophic effect of decidual tissue in the rat.     

Effect of oestrous cycle and early pregnancy on uterine production and expression of immune regulatory factors in gilts

This study was undertaken to characterize uterine immune factors involved in the establishment of pregnancy in gilts. Thirty crossbred Yorkshire-Landrace gilts of similar age and weight were observed twice a day for oestrous behaviour with intact boars. On the day of first standing oestrus (Day 0) and 12h later, 15 gilts were inseminated with pooled semen from Duroc boars of proven fertility. Pregnant gilts were slaughtered either on Days 10, 15 or 25 of gestation (n=5 per day). The other 15 gilts were not inseminated and were slaughtered on either Days 0, 10 or 15 of the oestrous cycle (n=5 per day). Immediately after slaughter, endometrial tissue samples from the mesometrial side were removed for gene expression using RNase protection assay and in situ hybridization methodologies. The other uterine horn was flushed with 20 ml of PBS to collect the uterine fluid. In pregnant gilts, endometrial interleukin (IL)-6 mRNA expression was higher on Day 15 than on Days 10 and 25 (P<0.01 and P<0.1, respectively). On Day 15, IL-6 expression was also significantly higher (P<0.01) in pregnant gilts than in cyclic gilts. In both pregnant and cyclic gilts, transforming growth factor (TGF)-beta2 in uterine fluid was significantly higher (P<0.0001) on Day 15 than on Day 10. At the gene expression level, TGF-beta2 also increased between Days 10 and 15 in both cyclic and pregnant gilts but differences were not significant. On Day 15, concentrations of interferon-gamma and prostaglandin E(2) (PGE(2)) in uterine fluid were markedly higher (P<0.001) in pregnant gilts than in cyclic gilts, whereas the total amount of TGF-beta2 in uterine fluid and its endometrial expression were approximately 70% higher although this increase was not significant. Finally, tumour-necrosis factor-alpha and granulocyte-macrophage/colony-stimulating factor mRNA expressions were undetectable in all endometrial samples. In conclusion, production and/or expression of uterine TGF-beta2, IL-6 and PGE(2) increased during the embryonic attachment period and are coincidental with embryonic interferon-gamma production.     

Plasma luteinizing hormone levels in normal and prenatally stressed male and female rat fetuses and their mothers

Concentrations of luteinizing hormone (LH) were measured in plasma of fetal and neonatal rats obtained from control mothers and from mothers exposed to stress from Days 14 to 21 of gestation. The regimen of stress used is known to be associated with an abnormal ontogenetic pattern of testosterone secretion from the fetal testes. The overall ontogenetic pattern of immunoreactive LH levels in plasma was similar in male and female rats, and was unaffected by stress. In all groups, LH was low from Days 16 to 20 of gestation, and then rose progressively through birth, i.e. Day 23. However, stressing the mother significantly decreased the already low levels of LH between Days 16 and 20, as indicated by a larger percentage of samples from stressed fetuses of both sexes with LH levels below the limit of sensitivity of the assay. Sex differences in both the control and stressed group became evident only after Day 20 of gestation, with plasma concentrations of females exceeding those of males from Day 21 to 23 post-conception.     

Ontogeny of secretory patterns of LH release and effects of gonadectomy in the chronically catheterized pig fetus and neonate

Two experiments were conducted to determine the ontogeny of secretory patterns of luteinizing hormone (LH) release and effects of gonadectomy on the characteristics of LH secretion in the chronically catheterized pig fetus and neonate. To study secretory patterns in intact animals, blood samples were collected from 44 pig fetuses and their mothers (Days 81, 99, 109 and 113 of gestation) as well as from 25 neonates (Days 4 and 8) every 15 min for 3 h (2 h on Day 81). The results indicate that the fetal adenohypophysis secretes occasional pulses of LH as early as Day 81 of fetal life. Fetal and maternal mean LH levels are low (0.25-0.50 ng/ml) at all gestational ages, with lowest values just before birth (Day 113 post coitum). Four-day-old neonates show a significant increase in pulse frequency (male and female) as well as pulse amplitude (female), relative to fetal values, leading to significant augmentations in mean LH levels. This is associated with reductions in both 17 beta-estradiol and progesterone. By 8 days of age significant sex differences in mean LH levels (males greater than females) appear. Testosterone/5 alpha-dihydrotestosterone levels (males) are low prenatally but are significantly increased after birth, possibly due to the stimulating effects of increasing LH levels. To study the gonadal control of LH secretion, forty-one 105-day-old fetuses and thirty-eight 4-day-old neonates were chronically catheterized and were either gonadectomized or remained as sham or control animals. Forty-eight and 96 h after surgery, blood samples were taken every 15 min for 3 h. No significant changes are detectable at 96 h in mean LH, pulse frequency and amplitude in female or male fetuses or in neonates. While significant reductions in testosterone levels are observed at 96 h in the male fetus and neonate, progesterone concentration is reduced only in the neonate. In the castrated female, on the other hand, neither fetus nor neonate display significant changes in circulating levels of progesterone and 17 beta-estradiol at 96 h. It is concluded that the pituitary of the pig is able to discharge LH with occasional pulses as early as Day 81 of fetal life; however, the pituitary remains suppressed until after birth, probably due to high circulating nongonadal steroids in the fetal compartment.     

Induction of catechol-O-methyltransferase in the luminal epithelium of rat uterus by progesterone

We performed light microscopic immunocytochemical observations of the localization of catechol-O-methyltransferase (COMT) in rat uterus, using a rabbit anti-rat serum specific for the soluble form of rat liver COMT, biotinylated goat anti-rabbit immunoglobulin, and peroxidase conjugated with streptavidin. In the non-pregnant rat, COMT was minimal but detectable in the uterine luminal and glandular epithelium, with greater amounts present in uteri from rats in estrus than those in diestrus. In early pregnancy a robust accumulation of COMT was observed in the luminal epithelium. To more precisely define both the timing and the factors contributing to the appearance of COMT, uteri were examined on Days 1-5 in pregnant and pseudopregnant rats. Accumulation of COMT in the luminal epithelium was observed by Day 3 in uteri from pregnant and pseudopregnant rats and by Day 4 in lactating post-partum rats. No immunostaining of COMT was observed in uteri from non-lactating post-partum rats. Ovariectomy on Day 0 or 1 but not on Day 2 of pregnancy prevented the appearance of COMT on Day 4. Progesterone treatment immediately after ovariectomy on Day 0 or 1 of pregnancy restored the COMT.     

The effect of aprotinin on luteolytic and uterine contractile mechanisms in the pregnant rat at term.

The effect of the kallikrein inhibitor aprotinin on luteal function, uterine activity and parturition was studied in primigravid pregnant rats. Luteal function was monitored by the determination of serum progesterone levels. Aprotinin given daily from Day 19 to Day 22 of gestation had no effect on progesterone concentrations compared to saline-treated controls, but indomethacin delayed the decline in progesterone levels over the same time period. Aprotinin treatment had no effect on fetal and placental weights from Days 19 to 22 of gestation. Aprotinin infusion in Day-22 pregnant rats resulted in a reduction in uterine motility (studied by continuous recording in conscious rats by means of an intrauterine microballoon) in 10/12 rats. Continuous infusion of aprotinin into rats which had been allowed to deliver one young resulted in a significantly prolonged duration of parturition compared to that in saline-infused controls. In one rat the delivery process was completely arrested and recommended only when the infusion was stopped. Aprotonin had no effect on either the spontaneous or oxytocin-induced uterine contractions of the isolated Day-22 pregnant rat uterus. It is concluded that the kallikrein-kinin system in the late pregnant rat does not appear to be involved in the luteolytic process but may play a functional role in the control of uterine and/or cervical function before and during parturition.     

Placental and fetal growth and development in late rat gestation is dependent on adrenomedullin

Adrenomedullin is a potent, endogenous vasodilator peptide synthesized and secreted by diverse locations such as adrenal glands, lungs, kidneys, vascular smooth muscle, and endothelium. Homozygous deletion of the adrenomedullin gene is embryonic lethal. We hypothesized that adrenomedullin has an important role in placental and fetal growth and development in rat pregnancy. The current study evaluated maternal systolic blood pressure, litter size, placental and pup weight, pup mortality, and placental pathology in pregnant rats following continuous in utero exposure to an adrenomedullin antagonist. Osmotic minipumps were inserted on Gestational Day 14 to continuously deliver either adrenomedullin, adrenomedullin antagonist, or vehicle control. Systolic blood pressure was recorded daily. Pregnant rats were killed on Gestational Day 15-18, 20, and/or 22 to evaluate placental development and fetal growth. The placentas were graded for the presence of necrosis in the decidua and fetal labyrinth as well as fetal vessel development in the labyrinth. A trend toward increased systolic blood pressure was noted between Gestational Days 17 and 20 in mothers treated with adrenomedullin antagonist, but the difference was not statistically significant. Antagonism of adrenomedullin function during rat pregnancy caused fetal growth restriction, decreased placental size, gross necrosis of placental margins and amniotic membranes, histologically deficient fetal vessel development in the labyrinth, and fetal edema. Adrenomedullin contributes to angiogenesis, functions as a growth factor, and helps regulate vascular tone during rat gestation.