The effects of alpha- and beta-adrenergic stimulation on contractility and prostaglandin (prostaglandins E2 and F2 alpha and 6-keto-prostaglandin F1 alpha) production of pregnant human myometrial strips

Noradrenaline and Adrenoreceptors Are Involved in the Regulation of Prostaglandin I2 Production in the Porcine Endometrium after Experimentally Induced Inflammation

Endometritis is a common disease in animals, leading to disruption of reproductive processes and economic losses. Noradrenergic control of prostaglandin (PG)I2 formation by inflamed endometrium is unknown. We determined the involvement of α1-, α2- and β-adrenoreceptors (ARs) in noradrenaline-influenced PGI synthase (PGIS) protein abundance and PGI2 release from porcine (1) endometrial explants with Escherichia coli (E. coli)-induced inflammation in vivo, and (2) E. coli lipopolysaccharide (LPS)-treated endometrial epithelial cells. Experiment 1. E. coli suspension (E. coli group) or saline (CON group) was injected into the uterine horns. In both groups, noradrenaline increased endometrial PGIS abundance and PGI2 release versus the control values, and it was higher in the E. coli group than in the CON group. In the CON group, a noradrenaline stimulating effect on both parameters takes place through α1D-, α2C- and β2-ARs. In the E. coli group, noradrenaline increased PGIS abundance and PGI2 release via α1A-, α2(B,C)- and β(1,2)-ARs, and PGI2 release also by α2A-ARs. Experiment 2. LPS and noradrenaline augmented the examined parameters in endometrial epithelial cells versus the control value. In LPS-treated cells, β(1,2)-ARs mediate in noradrenaline excitatory action on PGIS protein abundance and PGI2 release. β3-ARs also contribute to PGI2 release. Under inflammatory conditions, noradrenaline via ARs increases PGI2 synthesis and release from the porcine endometrium, including epithelial cells. Our findings suggest that noradrenaline may indirectly affect processes regulated by PGI2 in the inflamed uterus.

Role of Noradrenaline and Adrenoreceptors in Regulating Prostaglandin E2 Synthesis Cascade in Inflamed Endometrium of Pigs

In the inflamed uterus, the production and secretion of prostaglandins (PGs) and noradrenergic innervation pattern are changed. Receptor-based control of prostaglandin E2 (PGE2) production and secretion by noradrenaline during uterine inflammation is unknown. The aim of this study was to determine the role of α1-, α2- and β-adrenoreceptors (ARs) in noradrenaline-influenced PG-endoperoxidase synthase-2 (PTGS-2) and microsomal PTGE synthase-1 (mPTGES-1) protein levels in the inflamed pig endometrium, and in the secretion of PGE2 from this tissue. E. coli suspension (E. coli group) or saline (CON group) was injected into the uterine horns. Eight days later, severe acute endometritis developed in the E. coli group. Endometrial explants were incubated with noradrenaline and/or α1-, α2- and β-AR antagonists. In the CON group, noradrenaline did not significantly change PTGS-2 and mPTGES-1 protein expression and increased PGE2 secretion compared to the control values (untreated tissue). In the E. coli group, both enzyme expression and PGE2 release were stimulated by noradrenaline, and these values were higher versus the CON group. The antagonists of α1- and α2-AR isoforms and β-AR subtypes do not significantly alter the noradrenaline effect on PTGS-2 and mPTGES-1 protein levels in the CON group, compared to noradrenaline action alone. In this group, α1A-, α2B- and β2-AR antagonists partly eliminated noradrenaline-stimulated PGE2 release. Compared to the noradrenaline effect alone, α1A-, α1B-, α2A-, α2B-, β1-, β2- and β3-AR antagonists together with noradrenaline reduced PTGS-2 protein expression in the E. coli group. Such effects were also exerted in this group by α1A-, α1D-, α2A-, β2- and β3-AR antagonists with noradrenaline on mPTGES-1 protein levels. In the E. coli group, the antagonists of all isoforms of α1-ARs and subtypes of β-ARs as well as α2A-ARs together with noradrenaline decreased PGE2 secretion versus noradrenaline action alone. Summarizing, in the inflamed pig endometrium, α1(A, B)-, α2(A, B)- and β(1, 2, 3)-ARs mediate the noradrenaline stimulatory effect on PTGE-2 protein expression, while noradrenaline via α1(A, D)-, α2A- and β(2, 3)-ARs increases mPTGES-1 protein expression and α1(A, B, D)-, α2A- and β(1, 2, 3)-ARs are involved in PGE2 release. Data suggest that noradrenaline may indirectly affect the processes regulated by PGE2 by influencing its production. Pharmacological modulation of particular AR isoforms/subtypes can be used to change PGE2 synthesis/secretion to alleviate inflammation and improve uterine function.

Effect of blocking of alpha1-adrenoreceptor isoforms on the noradrenaline-induced changes in contractility of inflamed pig uterus

BACKGROUND

Disturbances in uterine contractility often lead to the origin, development and maintenance of endometritis and metritis, which are a very common and serious pathologies in domestic animals. Here we aimed to investigate the role of α1A-, α1B- and α1D-adrenoreceptors (ARs) in noradrenaline (NA)-induced contractility of inflammatory-changed porcine uterus.

METHODS

On Day 3 of the estrous cycle, either Escherichia coli (E. coli) suspension (E. coli group) or saline (SAL group) was injected into uterine horns, or only laparotomy was performed (CON group). Eight days later, infected gilts developed severe acute endometritis.

RESULTS

Compared to the period before NA application, NA reduced the contractile amplitude and frequency in myometrium (MYO) and endometrium (ENDO)/MYO strips from the CON, SAL and E. coli groups. In the last group, the amplitude in MYO and the frequency in ENDO/MYO were lowered versus other groups. After using α1A-ARs antagonist with NA, a greater decrease or occurrence of a drop in the amplitude and frequency in all groups (ENDO/MYO) were found compared to this neurotransmitter action alone. Such results were noted for NA action on the frequency after α1B-ARs blocking in the CON (both kinds of strips) and SAL (ENDO/MYO) groups. In response to α1D-ARs antagonist with NA, a greater decrease or occurrence of a drop in the amplitude was noted in the CON (both kinds of strips) and SAL and E. coli (MYO) groups. Use of these factors caused the similar changes in the frequency in CON and E. coli (MYO) and SAL (ENDO/MYO) groups. In response to NA, α1A,B,D-ARs antagonist led to a greater reduction or appearance of a drop in the amplitude in the CON and SAL (ENDO/MYO) and E. coli (both kinds of strips) as well as in the frequency in the CON and SAL (ENDO/MYO) and E. coli (MYO) groups.

CONCLUSIONS

In conclusion, activation of α1A- and α1D-ARs by NA promotes the contractile amplitude and frequency in the inflamed pig uterus; pharmacological modulation of these receptors can be utilized to enhance systolic activity of myometrium.

Analgesia during Parturition in Domestic Animals: Perspectives and Controversies on Its Use

This article analyzes the physiological role of pain during parturition in domestic animals, discusses the controversies surrounding the use of opioids, non-steroidal anti-inflammatory drugs (NSAIDs), and local analgesics as treatments during labor, and presents the advantages and disadvantages for mother and offspring. Labor is a potentially stressful and painful event, due to the contractions that promote expulsion of the fetus. During labor, neurotransmitters such as the prostaglandins contribute to the sensitization of oxytocin receptors in the myometrium and the activation of nociceptive fibers, thus supporting the physiological role of pain. Endogenously, the body secretes opioid peptides that modulate harmful stimuli and, at the same time, can inhibit oxytocin's action in the myometrium. Treating pain during the different stages of parturition is an option that can help prevent such consequences as tachycardia, changes in breathing patterns, and respiratory acidosis, all of which can harm the wellbeing of offspring. However, studies have found that some analgesics can promote myometrial contractility, increase expulsion time, affect fetal circulation, and alter mother-offspring recognition due to hypnotic effects. Other data, however, indicate that reducing the number of uterine contractions with analgesics increases their potency, thus improving maternal performance. Managing pain during labor requires understanding the tocolytic properties of analgesics and their advantages in preventing the consequences of pain.

Endometritis decreases the population of uterine neurons in the paracervical ganglion and changes the expression of sympathetic neurotransmitters in sexually mature gilts

BACKGROUND

The focus of the study was to examine the impact of the inflamed uterus on the population of the paracervical ganglion (PCG) uterus-innervating perikarya and their chemical coding. Fast Blue retrograde tracer was injected into the wall of uterine horns on the 17th day of the first studied estrous cycle. After 28 days, either Escherichia coli suspension or saline was applied to the horns of the uterus, whereas the control group received laparotomy only. Eight days after the above-mentioned procedures, uterine cervices with PCG were collected. Both macroscopic and histopathologic examinations confirmed severe acute endometritis in the Escherichia coli-injected uteri. The double immunofluorescence method was used to analyze changes in the PCG populations coded with dopamine-β-hydroxylase (DβH) and/or neuropeptide Y (NPY), somatostatin (SOM), vasoactive intestinal polypeptide (VIP) and neuronal isoform of nitric oxide synthase (nNOS).

RESULTS

The use of Escherichia coli lowered the total number of Fast Blue-positive neurons. Moreover, an increase in DβH+/VIP+, DβH+/NPY+, DβH+/SOM + and DβH+/nNOS + expressing perikarya was noted. A rise in non-noradrenergic VIP-, SOM- and nNOS-immunopositive populations was also recorded, as well as a drop in DβH-positive neurotransmitter-negative neurons.

CONCLUSIONS

To sum up, inflammation of the uterus has an impact on the neurochemical properties of the uterine perikarya in PCG, possibly affecting the functions of the organ.

Role of beta-adrenergic receptor subtypes in pig uterus contractility with inflammation

Uterine inflammation is a very common and serious condition in domestic animals. To development and progression of this pathology often lead disturbances in myometrial contractility. Participation of β1-, β2- and β3-adrenergic receptors (ARs) in noradrenaline (NA)-influenced contractility of the pig inflamed uterus was studied. The gilts of SAL- and E.coli-treated groups were administered saline or E.coli suspension into the uterine horns, respectively. Laparotomy was only done in the CON group. Compared to the period before NA administration, this neurotransmitter reduced the tension, amplitude and frequency in uterine strips of the CON and SAL groups. In the E.coli group, NA decreased the amplitude and frequency, and these parameters were lower than in other groups. In the CON, SAL and E.coli groups, β1- and β3-ARs antagonists in more cases did not significantly change and partly eliminated NA inhibitory effect on amplitude and frequency, as compared to NA action alone. In turn, β2-ARs antagonist completely abolished NA relaxatory effect on these parameters in three groups. Summarizing, NA decreases the contractile amplitude and frequency of pig inflamed uterus via all β-ARs subtypes, however, β2-ARs have the greatest importance. Given this, pharmacological modulation of particular β-ARs subtypes can be used to increase inflamed uterus contractility.

Beta-2 Agonists May be Superior to Epinephrine to Relieve Severe Anaphylactic Uterine Contractions

BACKGROUND

Uterine contractions are recognized as a potential manifestation of anaphylaxis, but literature on their proper management is limited. It is widely recognized that anaphylactic reactions can cause uterine contractions, but little is known about their optimal management.

OBJECTIVE

Review potential treatments for painful uterine contractions associated with anaphylaxis or mast cell activation.

METHODS

This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guidelines. PubMed, Embase, and Cochrane were searched in English, French, and Spanish for reports of uterine anaphylaxis published up until July 2020. The search strategy used a combination of Boolean operators and included the following Medical Subject Heading terms and keywords: hypersensitivity; anaphylaxis; mastocytosis; uterus; uterine contraction; pelvic pain; labor, obstetric; labor, premature; and endometriosis.

RESULTS

This systematic review identified 19 studies reporting on 31 cases of painful uterine contractions occurring during anaphylaxis or other events associated with mast cell activation. Nine patients were pregnant. We present 2 additional cases in nonpregnant women, one associated with an oral food challenge and the other associated with oral food desensitization. The most frequent triggers were subcutaneous immunotherapy (14 cases), food (6 cases), and drugs (4 cases). Uterine cramps were associated with systemic symptoms in 24 cases and lasted on average for 2.4 hours. Pretreatment with antihistamines and montelukast generally failed to prevent recurrence, but nonsteroidal anti-inflammatory drugs were used successfully in some reports. Response to intramuscular epinephrine was inconsistent. Data from ex vivo models indicate that epinephrine may paradoxically contribute to uterine contractions through alpha-receptor activity. A small number of cases showed good response to beta-2 agonists.

CONCLUSIONS

There is a lack of quality data on painful uterine contractions occurring in the context of anaphylactic reactions and on their optimal management. In the absence of counterindication, use of a beta-2 agonist and premedication with nonsteroidal anti-inflammatory drugs could be the preferred options.

Endometritis Changes the Neurochemical Characteristics of the Caudal Mesenteric Ganglion Neurons Supplying the Gilt Uterus

Simple Summary

Uterine inflammation is a very frequent pathology in domestic animals leading to disturbances in reproductive processes and causing significant economic losses. The uterus possesses nerves from either the autonomic or sensory part of the peripheral nervous system. Most of the uterus-projecting neurons are localized in the caudal mesenteric ganglion. These neurons synthesize and release numerous biologically active substances in the uterus, which regulate uterine functions. The effect of inflammation on uterine innervation is poorly recognized. This study showed that Escherichia coli-induced uterine inflammation in pig led to a reduction in the total population of uterine neurons in the caudal mesenteric ganglion, and in the populations of these cells in the dorsal and central areas of this ganglion. In the caudal mesenteric ganglion of gilts after intrauterine bacterial injection, the population of uterine neurons presenting positive staining for dopamine-β-hydroxylase (an enzyme participating in noradrenaline synthesis) and negative staining for galanin, as well as the population of uterine neurons presenting negative staining for dopamine-β-hydroxylase but positive staining for neuropeptide Y, were decreased. In these gilts, there were increased numbers of uterine neurons which, besides dopamine-β-hydroxylase, also expressed neuropeptide Y, galanin and vasoactive intestinal peptide. The above changes suggest that inflammation of the gilt uterus may affect the function(s) of this organ by its action on the neurons of the caudal mesenteric ganglion.

Abstract

This study analyzed the influence of uterine inflammation on the neurochemical characteristics of the gilt caudal mesenteric ganglion (CaMG) uterus-supplying neurons. The horns of uteri were injected with retrograde tracer Fast Blue on day 17 of the first studied estrous cycle. Twenty-eight days later (the expected day 3 of the third studied estrous cycle), either saline or Escherichia coli suspension were administered into each uterine horn. Only the laparotomy was done in the control gilts. After 8 days, the CaMGs and uteri were harvested. The infected gilts presented a severe acute endometritis. In the CaMGs, the populations of uterine perikarya possessing dopamine-β-hydroxylase (DβH) and/or neuropeptide Y (NPY), somatostatin (SOM), galanin (GAL) and vasoactive intestinal polypeptide (VIP) were analyzed using the double immunofluorescence method. In the CaMG, bacterial injection decreased the total number of the perikarya (Fast Blue-positive), the small and large perikarya populations in the dorsal and central regions, and the small and large perikarya populations coded DβH+/GAL- and DβH-/NPY+. After bacterial treatment, there was an increase in the numbers of small and large perikarya coded DβH+/NPY+, small perikarya coded DβH+/GAL+ and DβH+/SOM- and large perikarya coded DβH+/VIP+. To summarize, uterine inflammation influences the neurochemical characteristics of the CaMG uterus-supplying neurons, which may be important for pathologically changed organ functions.

Increased hypothalamic hydrogen sulphide contributes to endotoxin tolerance by down-modulating PGE2 production

AIM

Whereas some patients have important changes in body core temperature (Tb) during systemic inflammation, others maintain a normal Tb, which is intrinsically associated to immune paralysis. One classical model to study immune paralysis is the use of repeated administration of lipopolysaccharide (LPS), the so-called endotoxin tolerance. However, the neuroimmune mechanisms of endotoxin tolerance remain poorly understood. Hydrogen sulphide (H₂ S) is a gaseous neuromodulator produced in the brain by the enzyme cystathionine β-synthase (CBS). The present study assessed whether endotoxin tolerance is modulated by hypothalamic H₂ S.

METHODS

Rats with central cannulas (drug microinjection) and intraperitoneal datalogger (temperature record) received a low-dose of lipopolysaccharide (LPS; 100 µg kg^-1 ) daily for four consecutive days. Hypothalamic CBS expression and H₂ S production rate were assessed, together with febrigenic signalling. Tolerant rats received an inhibitor of H₂ S synthesis (AOA, 100 pmol 1 µL^-1 icv) or its vehicle in the last day.

RESULTS

Antero-ventral preoptic area of the hypothalamus (AVPO) H₂ S production rate and CBS expression were increased in endotoxin-tolerant rats. Additionally, hypothalamic H₂ S inhibition reversed endotoxin tolerance reestablishing fever, AVPO and plasma PGE₂ levels without altering the absent plasma cytokines surges.

CONCLUSION

Endotoxin tolerance is not simply a reflection of peripheral reduced cytokines release but actually results from a complex set of mechanisms acting at multiple levels. Hypothalamic H₂ S production modulates most of these mechanisms.

Expression of alpha and beta adrenergic receptors in the pig uterus during inflammation

Under physiological conditions, noradrenaline (NA) and adrenergic receptors (ARs) are implicated in the function of the uterus. The role of NA and the expression of ARs in the inflamed uterus is not fully understood. The aim of the present study was to determine the effect of inflammation on the levels of α1 (A, B, D)-, α2 (A, B, C)- and β (1, 2, 3)-ARs mRNA and protein expression and the localization of these receptors in the porcine uterus. On Day 3 of the estrous cycle (Day 0 of the study), 50 ml of either saline (group SAL) or E. coli suspension (10⁹ colony-forming units/ml, group E. coli) were injected into each uterine horn. In the control pigs (group CON), only laparotomy was performed. Eight days later, α1D-ARs mRNA (P < 0.001) and protein (P < 0.05) levels and α2A-ARs protein level (P < 0.05) were increased in the inflamed endometrium, while the α2C-ARs protein level (P < 0.001) was lowered, as compared to the SAL and CON groups. In the inflamed endometrium, β2-ARs mRNA (P < 0.01) and protein (CON: P < 0.01, SAL: P < 0.001) expression was lower than in the other two groups, and β1-ARs mRNA (P < 0.001) and protein (P < 0.01) expression was higher compared to the SAL group. After bacterial treatment, α2A- (P < 0.001) and α2B (P < 0.05) -ARs protein levels and β2-ARs mRNA (CON: P < 0.01, SAL: P < 0.05) and protein (CON: P < 0.01, SAL: P < 0.05) expression in myometrium were found to be increased compared to both groups. In turn, in myometrium following E. coli infusion, the α2C-ARs protein level was lower (P < 0.01) than in the CON group. All studied receptors were present in the luminal and glandular epithelium, blood vessels and myometrial muscular cells of the gilt uteri in the E. coli, SAL and CON groups. The data show that inflammation changes the ARs expression in porcine uterus, suggesting their importance in the course/consequences of uterine inflammation. Those affected ARs may constitute a therapeutic target in an inflamed uterus.

Maternal catecholamine levels in midpregnancy and risk of preterm delivery

Associations between stress hormones and preterm delivery have not been fully explored. In this study, pregnant women enrolled from 52 clinics in 5 Michigan communities (1998-2004) provided urine samples for 3 days (waking and bedtime) during midpregnancy. Urinary catecholamine levels (epinephrine, norepinephrine, and dopamine) were measured in a subcohort (247 preterm and 760 term deliveries), and a 3-day median value was calculated. Polytomous logistic regression models assessed relations between catecholamine quartiles (of the median) and a 4-level outcome variable (i.e., term (referent) and 3 preterm delivery subtypes: spontaneous; premature rupture of membranes; and medically indicated). Final models incorporated other relevant covariates (e.g., creatinine, demographic, behavior). The risk of spontaneous preterm delivery was increased in the highest versus lowest quartile of norepinephrine and dopamine: norepinephrine, waking (adjusted odds ratio (AOR) = 3.7, 95% confidence interval (CI): 1.8, 7.9) and bedtime (AOR = 2.5, 95% CI: 1.3, 4.9); dopamine, waking (AOR = 2.6, 95% CI: 1.4, 5.1) and bedtime (AOR = 2.3, 95% CI: 1.2, 4.6). Adjusted odds ratios were further strengthened after removing women whose placentas showed evidence of acute infection or vascular pathology. High catecholamine levels in maternal urine may be indicative of excess stressors and/or predisposition to elevated sympathetic activation that contributes to increased risk of spontaneous preterm delivery.

The regulation of uterine relaxation

The regulation of uterine relaxation is poorly understood but research in myometrial tissue and other types of smooth muscle has defined a number of receptors, ion channels and regulatory proteins that are likely to be involved. Some of these proteins are substrates for protein kinases, especially cyclic nucleotide dependent kinases. More research is necessary to identify the key molecules involved in the maintenance of uterine quiescence in pregnancy. The use of tocolytics in preterm labour remains controversial; there is a need to identify better pharmacological targets to provoke safe and selective uterine relaxation and improve neonatal outcome.

The in vitro effects of clonidine and dexmedetomidine on human myometrium

BACKGROUND

alpha(2)-adrenergic agonists have been used extensively in the field of anaesthesia. Their direct effect on the human myometrium was investigated in this in vitro study, as this may have clinical repercussions in obstetric anaesthesia.

METHOD

Strips of pregnant human myometrium obtained from six individuals at elective caesarean section were mounted on the Mulvany myograph in Krebs solution to which increasing concentrations of clonidine and dexmedetomidine (1x10(-11) to 1x10(-6) g/mL) were added.

RESULTS

Dexmedetomidine increased uterine contractility at simulated clinical plasma concentrations (1x10(-9) g/mL). These effects were seen with clonidine only at much higher tissue bath concentrations (1x10(-7) g/mL).

CONCLUSION

The effect of dexmedetomidine on human myometrium has profound implications in obstetric anaesthesia and needs further clinical investigation.

Effect of an acute ergotamine challenge on reproductive hormones in follicular phase heifers and progestin-treated cows

The objective of this research was to determine if ergotamine, an ergopeptine alkaloid isolated from Neotyphodium-infected grasses and associated with toxicoses in livestock, altered plasma concentrations of reproductive hormones in follicular phase heifers and in cows given a progestin implant. In Experiment 1, blood was sampled for 8h from four cycling heifers 2 days after synchronized luteolysis. Heifers were treated with ergotamine tartrate (19microg/kg) i.v. or saline vehicle in a simple cross-over design after 1h of pre-treatment blood sampling. Heifers received oxytocin (100USP units) i.v. 4h after ergotamine or saline treatment. Ergotamine reduced (P<0.01) prolactin concentrations from 1 to 4h post-treatment and increased (P<0.01) 13,14-dihydro-15-keto prostaglandin F2alpha (PGFM) concentrations from 2 to 5h post-treatment. A PGFM response to oxytocin was not detected. In Experiment 2, blood was sampled for 8h from six cycling cows 10 days after receiving a s.c. norgestomet implant. Cows were treated i.v. with ergotamine (20microg/kg) or saline in a simple cross-over design after 1h of pre-treatment blood sampling. Cows received gonadorelin (GnRH, 100microg) i.v. 1h after ergotamine or saline. Cows received oxytocin (100USP units) i.v. 4h after ergotamine or saline treatment. Ergotamine reduced (P<0.01) serum prolactin concentrations by 120min after treatment, with prolactin returning to pre-treatment concentrations by 200min after treatment. Saline-treated cows had lower (P<0.01) prolactin by 280min after treatment. Ergotamine-treated cows had higher (P<0.01) PGFM concentrations compared to saline-treated cows 120-240min after treatments, but the groups exhibited similar increases in PGFM after oxytocin. Plasma LH and FSH concentrations increased to peaks 100-120min after GnRH for both groups. However, the LH response to GnRH was greater (P<0.01) for ergotamine-treated cows. In summary, ergotamine lowered prolactin and elevated PGFM concentrations in follicular phase heifers and cows on norgestomet therapy. Ergotamine increased the LH response to exogenous GnRH in cows with norgestomet implants. These data highlight the potential of ergopeptine alkaloids to affect reproduction through altered endocrine function.

Longitudinal study of beta- and alpha-adrenergic receptor properties during human pregnancy

OBJECTIVE

Our goal was to ascertain whether alterations in beta- and alpha-adrenergic receptor number and function (cyclic adenosine monophosphate production) occur during and after pregnancy. Because the actions of beta- and alpha2-adrenergic receptors tend to oppose each other, we hypothesized that there might be progressive, possibly reciprocal changes in these receptors during and after pregnancy.

STUDY DESIGN

Blood was obtained from 21 women at 10, 20, 30, and 37 weeks of pregnancy and 3 to 4 months post partum. Lymphocyte beta- and platelet alpha2-adrenergic receptor number and affinity were quantified by radioligand binding studies, and receptor function was assessed by cyclic adenosine monophosphate generation assays.

RESULTS

Although there were suggestions of progressive alterations in some of the variables studied, beta- and alpha2-adrenergic receptor number, affinity, and function did not manifest any statistically significant changes.

CONCLUSION

Pregnancy did not produce marked alterations in beta-adrenergic receptor or alpha2-adrenergic receptor properties.

Human placental monoamine transporters as targets for amphetamines

OBJECTIVES

The use of amphetamine and its derivatives during pregnancy is known to have adverse effects on the outcome of pregnancy. These effects are at least partly a result of impairment of placental function caused by these abusable drugs. We hypothesized that the two monoamine transporters, namely, the serotonin transporter and the norepinephrine transporter, that are expressed in the human placenta are direct targets for these drugs.

STUDY DESIGN

The interaction of amphetamine and methamphetamine with human placental serotonin and norepinephrine transporters was examined. Activity of the serotonin transporter was assessed by serotonin uptake in both maternal-facing brush border membrane vesicles isolated from normal term human placentas and in JAR choriocarcinoma cells. Activity of the norepinephrine transporter was assessed by dopamine uptake and nisoxetine binding in placental brush border membrane vesicles.

RESULTS

Amphetamine and methamphetamine are potent inhibitors of the serotonin and norepinephrine transporters expressed in the human placenta. The inhibitory potency of amphetamine is greater than that of methamphetamine. In each case, the S(+)diastereoisomer is more potent than the corresponding R(-)diastereoisomer. The sensitivity of the norepinephrine transporter to inhibition by these drugs is at least two orders of magnitude greater than that of the serotonin transporter. At concentrations known to occur in the plasma of users, these drugs cause a marked inhibition of the norepinephrine transporter.

CONCLUSIONS

The results show that the norepinephrine transporter and, to a lesser extent, the serotonin transporter are cellular targets in the human placenta for the abusable drugs amphetamine and methamphetamine.

Intravenous administration of cocaine stimulates gravid baboon myometrium in the last third of gestation

OBJECTIVE

The hypothesis for this investigation was that intravenous cocaine results in a dose-dependent increase in myometrial activity of the unanesthetized, chronically instrumented gravid nonhuman primate.

STUDY DESIGN

Seven chronically instrumented gravid baboons were individually caged in an environment of 14 hours of light and 10 hours of darkness. Maternal femoral artery and vein catheters and three pairs of myometrial electromyographic wires were surgically placed at 90 to 121 days' gestation (term 180 days). At least 5 days after surgery, bolus intravenous cocaine hydrochloride doses of 0.05, 0.1, 0.3, 0.5, and 1.0 mg/kg maternal body weight were administered according to various schedules. Myometrial activity was analyzed by quantifying the myometrial electromyographic envelope data as the power spectral density window of contraction activity and as the total area under the rectified electromyographic voltage signal (i.e., total electromyographic activity) before and during the experimental period.

RESULTS

Myometrial contraction activity increased after the 0.3 mg/kg dose (p < 0.01), the 0.5 mg/kg dose (p < 0.005), and the 1.0 mg/kg dose (p = 0.07) compared with baseline. The total myometrial electromyographic activity also increased as the cocaine dose increased.

CONCLUSION

Intravenous cocaine results in increased myometrial contractions in the gravid baboon during the latter third of pregnancy.

Arachidonic acid metabolism and prostaglandin production by primate preimplantation blastocysts

Preimplantation embryos of many species are known to synthesize prostaglandins. These tissue hormones are believed to influence embryonic metabolism, as well as embryo-maternal interaction during implantation although their putative role(s) remains obscure. Here, prostaglandin production by blastocysts from cynomolgus monkeys (Macaca fascicularis) was examined qualitatively during in vitro culture. Tritium labelled arachidonic acid was metabolized to 6 keto-prostaglandin F1 alpha, 2,3-dinor-prostaglandin F1 alpha and thromboxane B2, as characterized by HPLC separation. Also, 6-keto-prostaglandin F1 alpha, and thromboxane B2 as characterized by HPLC separation. Also, 6-keto-prostaglandin F1 alpha and thromboxane B2 were identified by specific RIA's. Our data suggest that the main arachidonic acid metabolites produced by blastocysts of cynomolgus monkeys are prostacyclin and thromboxane.

Alpha 2-adrenergic receptors in guinea pig myometrium in late pregnancy: evidence for a predominantly postjunctional location

Uterine sympathetic nerves can exert an excitatory influence during pregnancy and parturition. Myometrial alpha 2-adrenergic receptor density falls sharply late in gestation, and diminished presynaptic neuromodulation could contribute to increased norepinephrine release reported at this time. Two studies were performed to investigate this potentially important mechanism. First, when alpha 2-adrenergic receptors were measured in well-innervated (tubal end and cervix), denervated (perifetal), and richly vascularized regions (placental) of late pregnant guinea pig uteri with the selective radioligand [3H]rauwolscine, high levels were detected in perifetal myometrium, particularly outside the site of placental implantation. Second, we report an unsuccessful attempt to demonstrate alpha 2-adrenergic receptor-mediated feedback suppression of electrically stimulated norepinephrine release from tubal and cervical regions of nonpregnant, midterm, and late-pregnant uteri. Together these results suggest that guinea pig myometrial alpha 2-adrenergic receptors are located mostly postjunctionally and are not associated with the vasculature. Thus an alpha 2-adrenergic feedback mechanism is unlikely to play an important role regulating uterine sympathetic neurotransmission.

The effect of cortisol on the synthesis of prostaglandins (PGF2 alpha, PGE2) by human endometrial fibroblasts in vitro with and without addition of estradiol-17 beta or progesterone

Cortisol is known as a potent inhibitor of phospholipase A2 activity in several tissues. In fibroblast monolayer cell cultures from proliferative human endometrium cortisol alone does not affect the basal PGF2 alpha or PGE2 synthesis. After stimulation of PGF2 alpha production by 10(-7) mol/l estradiol-17 beta increasing concentrations of cortisol up to 10(-5) mol/l dosedependently reduce the PGF2 alpha production. Also the progesterone (10(-4) mol/l) stimulated increase of PGF2 alpha and PGE2 synthesis is inhibited by cortisol (10(-7) mol/l).

The effect of clomiphene on the synthesis of prostaglandins (PGF2 alpha, PGE2, PGI2) in human endometrial cells in vitro with and without addition of estradiol-17 beta or progesterone

The production of prostaglandin F2 alpha in monolayer stromal cell cultures of proliferative human endometrium is enhanced by 10(-7) mol/l estradiol-17 beta or 10(-4) mol/l progesterone. Progesterone in high concentration (10(-4) mol/l) also enhanced the synthesis of prostaglandin E2. Clomiphene citrate reduced this increased prostaglandin production dose dependently. The synthesis of prostaglandin I2 was not influenced either by sex steroids or by clomiphene citrate.

A role for phosphoinositide hydrolysis in human uterine smooth muscle during parturition

Phosphoinositide hydrolysis is thought to be important in regulating a variety of intracellular signals, including Ca++ and prostaglandins, both of which have been implicated in the action of oxytocin during uterine smooth muscle contraction. We investigated the in vitro effect of oxytocin and various other uterotonic agents on phosphoinositide hydrolysis in gestational myometrium by measuring the production of inositol phosphates in tissue explants prelabeled with 3H-inositol. Oxytocin caused significant increases in all three inositol phosphates in myometrium at 3 minutes. Stimulation of inositol monophosphate production was sustained for 30 minutes and was dose dependent, with a half-maximal effect around 2 X 10(-8) mol/L. Platelet activating factor and alpha-adrenergic agonists also stimulated myometrial phosphoinositide hydrolysis, but carbachol prostaglandins E2 and F2 alpha had no effect. Vasopressin had greater efficacy than oxytocin for stimulating hydrolysis in gestational myometrium. Furthermore, in contrast to vasopressin, oxytocin had no effect on inositol phosphate production in nongestational myometrium. Oxytocin also stimulated arachidonic acid release and prostaglandin E2 and F2 alpha production in gestational myometrium. The hydrolysis of phosphatidylinositol by myometrium homogenates showed a precursor-product relationship for the production of diacylglycerol, monoacylglycerol, and arachidonic acid, indicative of a sequential action of phospholipase C and diacylglycerol lipase. These data demonstrate the potential for certain uterotonic agonists to use inositol lipid signaling to mobilize free arachidonic acid for prostaglandin production and to release intracellular Ca++ during excitation-contraction coupling.

[3H]rauwolscine binding to myometrial alpha 2-adrenoceptors in pregnant guinea pig

Uterine sympathetic nerves can exert an excitatory influence in late pregnancy and during parturition. Neuronal norepinephrine release is increased at these times and a diminished alpha 2-adrenoceptor-mediated prejunctional inhibition could account for this. To assess whether an altered receptor population may contribute, [3H]rauwolscine was used to measure alpha 2-adrenoceptors in myometrial membranes at time intervals throughout pregnancy. High affinity [3H]rauwolscine binding [Kd = 11.4 +/- 1.5 nM (n = 42)] yielded linear Scatchard plots that in nonpregnant myometrium indicated a maximum binding density (Bmax) of 217 +/- 42.4 fmol/mg protein. alpha 2-Adrenoceptor density was increased twofold at midpregnancy (31 days) and thereafter fell sharply by up to 90% toward term (67 +/- 2 days). When uterine growth is accounted for and data are expressed in terms of total myometrial population (uncorrected for plasma membrane recovery), alpha 2-adrenoceptor number was eightfold (midpregnancy) and fourfold (term) greater than the nonpregnant value of 804 +/- 322.4 fmol/uterus. alpha 2-Adrenoceptors were also found to bind dopamine with high affinity [Ki = 3.66 +/- 0.45 microM (n = 3)]. These observations could indicate a pregnancy-related change in uterine sympathetic autoinhibitory capacity and, since alpha 2-adrenoceptors appear also to be located postjunctionally, explain in part reports of altered myometrial responsiveness to norepinephrine infusion and also the uterotonic actions of dopamine.

Effects of estradiol-17 beta and progesterone on the synthesis of prostaglandin F2 alpha, prostaglandin E2 and prostaglandin I2 by fibroblasts from human endometrium in vitro

Estradiol-17 beta increases the production of prostaglandin F2 alpha (PGF2 alpha) in long term monolayer cell cultures of the human endometrium in a dose dependent manner. Progesterone in pharmacological dosage stimulates the syntheses of PGF2 alpha and of prostaglandin E2 (PGE2). The synthesis of prostaglandin I2 (PGI2) is not influenced by sex steroids in long term monolayer cell cultures of the human endometrium.

Involvement of alpha-adrenoceptors in myometrial responses in the pro-oestral rat

1. Myometrial responses to different agents acting on adrenoceptors were examined in vivo in the pro-oestrous rat. Changes in spontaneous uterine mechanical activity were recorded isometrically and evaluated in terms of amplitude and duration of uterine contractions. 2. Phenylephrine (10 micrograms kg-1) markedly increased the amplitude and duration of contractions and 40 micrograms kg-1 gave rise to tetanic contractions. 3. Administration of either nicergoline (400 micrograms kg-1) or phentolamine (1000 micrograms kg-1) to phenylephrine-primed rat uterus reduced the strength of contractions and phentolamine abolished the phenylephrine-induced uterine contracture. 4. Following blockade of alpha 2-adrenoceptors by yohimbine (1000 micrograms kg-1) and beta-adrenoceptors by propranolol (2400 micrograms kg-1), a single injection of phenylephrine (100 micrograms kg-1) increased the amplitude of uterine contractions by 30%. 5. Noradrenaline reduced the amplitude of contractions and caused elevation of the baseline level. The response of myometrium to the combination of both propranolol and noradrenaline was the establishment of uterine contracture with subsequent increase of the duration of contractions. 6. These results clearly demonstrate the involvement of alpha-adrenoceptors in the myometrial activity of the rat in vivo during pro-oestrus.

The effect of acetylsalicylic acid and indomethacin on the catecholamine- and oxytocin-induced contractility and prostaglandin (6-keto-PGF1 alpha, PGF2 alpha)-production of human pregnant myometrial strips

The effects of acetylsalicylic acid (ASA) and indomethacin (IND) on the epinephrine and oxytocin stimulated contractility and prostaglandin (6-keto-PGF1 alpha, PGF2 alpha) production of superfused myometrial strips from the pregnant human uterus at term are reported. Without preincubation in ASA or IND epinephrine dose-dependently (10 ng/ml to 1 microgram/ml) stimulated the contractility and significantly increased the PG-release of the myometrial strips. The epinephrine induced increase in contractility was correlated to a higher increase in PGF2a production and a decreased 6-keto-PGF1 alpha/PGF2 alpha ratio (5.4 to 1.8). Superfusion of oxytocin increased myometrial contractions and PGF2 alpha release according to dose (3-12 microU/ml). However, 6-keto-PGF1 alpha production was not affected by oxytocin. Myometrial strips preincubated with ASA (100 micrograms/ml) or IND (10 micrograms/ml) demonstrated little spontaneous activity and the PG production was below the detection limit of the RIA. The stimulating effect of epinephrine and oxytocin on the contractility and PGF2 alpha release of the myometrial strips was inhibited significantly. During continuous superfusion of the ASA and IND preincubated myometrial strips with Tyrode's solution the inhibitory effect on spontaneous, epinephrine-, and oxytocin-stimulated contractility and PGF2 alpha release gradually declined over a period of 2 hours. This decrease of the inhibitory effect was more significant in ASA preincubated specimens. Our results demonstrate that spontaneous, epinephrine-, and oxytocin-stimulated contractility and PG release of human myometrial strips can be inhibited by ASA and IND and that this inhibitory effect is reversible. Furthermore our results suggest that in pregnant human myometrium the inhibition of PGF2 alpha production by ASA and IND is more pronounced than that of 6-keto-PGF1 alpha (PGI2).