Placental transfer of catecholamines in vitro and in vivo

How is prenatal stress transmitted from the mother to the fetus?

Prenatal stress programmes long-lasting neuroendocrine and behavioural changes in the offspring. Often this programming is maladaptive and sex specific. For example, using a rat model of maternal social stress in late pregnancy, we have demonstrated that adult prenatally stressed male, but not prenatally stressed female offspring display heightened anxiety-like behaviour, whereas both sexes show hyperactive hypothalamo-pituitary-adrenal (HPA) axis responses to stress. Here, we review the current knowledge of the mechanisms underpinning dysregulated HPA axis responses, including evidence supporting a role for reduced neurosteroid-mediated GABAergic inhibitory signalling in the brains of prenatally stressed offspring. How maternal psychosocial stress is signalled from the mother to the fetuses is unclear. Direct transfer of maternal glucocorticoids to the fetuses is often considered to mediate the programming effects of maternal stress on the offspring. However, protective mechanisms including attenuated maternal stress responses and placental 11β-hydroxysteroid dehydrogenase-2 (which inactivates glucocorticoids) should limit materno-fetal glucocorticoid transfer during pregnancy. Moreover, a lack of correlation between maternal stress, circulating maternal glucocorticoid levels and circulating fetal glucocorticoid levels is reported in several studies and across different species. Therefore, here we interrogate the evidence for a role for maternal glucocorticoids in mediating the effects of maternal stress on the offspring and consider the evidence for alternative mechanisms, including an indirect role for glucocorticoids and the contribution of changes in the placenta in signalling the stress status of the mother to the fetus.

Functional characterization of dopamine and norepinephrine transport across the apical and basal plasma membranes of the human placental syncytiotrophoblast

The human placenta represents a unique non-neuronal site of monoamine transporter expression, with pathophysiological relevance during the prenatal period. Monoamines (serotonin, dopamine, norepinephrine) are crucial neuromodulators for proper placenta functions and fetal development, including cell proliferation, differentiation, and neuronal migration. Accumulating evidence suggests that even a transient disruption of monoamine balance during gestation may lead to permanent changes in the fetal brain structures and functions, projecting into adulthood. Nonetheless, little is known about the transfer of dopamine and norepinephrine across the placental syncytiotrophoblast. Employing the method of isolated membranes from the human term placenta, here we delineate the transport mechanisms involved in dopamine and norepinephrine passage across the apical microvillous (MVM) and basal membranes. We show that the placental uptake of dopamine and norepinephrine across the mother-facing MVM is mediated via the high-affinity and low-capacity serotonin (SERT/SLC6A4) and norepinephrine (NET/SLC6A2) transporters. In the fetus-facing basal membrane, however, the placental uptake of both monoamines is controlled by the organic cation transporter 3 (OCT3/SLC22A3). Our findings thus provide insights into physiological aspects of dopamine and norepinephrine transport across both the maternal and fetal sides of the placenta. As monoamine transporters represent targets for several neuroactive drugs such as antidepressants, our findings are pharmacologically relevant to ensure the safety of drug use during pregnancy.

Giving a good start to a new life via maternal brain allostatic adaptations in pregnancy

Successful pregnancy requires adjustments to multiple maternal homeostatic mechanisms, governed by the maternal brain to support and enable survival of the growing fetus and placenta. Such adjustments fit the concept of allostasis (stability through change) and have a cost: allostatic load. Allostasis is driven by ovarian, anterior pituitary, placental and feto-placental hormones acting on the maternal brain to promote adaptations that support the pregnancy and protect the fetus. Many women carry an existing allostatic load into pregnancy, from socio-economic circumstances, poor mental health and in 'developed' countries, also from obesity. These pregnancies have poorer outcomes indicating negative interactions (failing allostasis) between pre-pregnancy and pregnancy allostatic loads. Use of animal models, such as adult prenatally stressed female offspring with abnormal neuroendocrine, metabolic and behavioural phenotypes, to probe gene expression changes, and epigenetic mechanisms in the maternal brain in adverse pregnancies are discussed, with the prospect of ameliorating poor pregnancy outcomes.

Impact of chronic maternal stress during early gestation on maternal-fetal stress transfer and fetal stress sensitivity in sheep

Acute stress-induced reduction of uterine blood flow (UBF) is an indirect mechanism of maternal-fetal stress transfer during late gestation. Effects of chronic psychosocial maternal stress (CMS) during early gestation, as may be experienced by many working women, on this stress signaling mechanism are unclear. We hypothesized that CMS in sheep during early gestation augments later acute stress-induced decreases of UBF, and aggravates the fetal hormonal, cardiovascular, and metabolic stress responses during later development. Six pregnant ewes underwent repeated isolation stress (CMS) between 30 and 100 days of gestation (dGA, term: 150 dGA) and seven pregnant ewes served as controls. At 110 dGA, ewes were chronically instrumented and underwent acute isolation stress. The acute stress decreased UBF by 19% in both the CMS and control groups (p < .05), but this was prolonged in CMS versus control ewes (74 vs. 30 min, p < .05). CMS increased fetal circulating baseline and stress-induced cortisol and norepinephrine concentrations indicating a hyperactive hypothalamus-pituitary-adrenal (HPA)-axis and sympathetic-adrenal-medullary system. Increased fetal norepinephrine is endogenous as maternal catecholamines do not cross the placenta. Cortisol in the control but not in the CMS fetuses was correlated with maternal cortisol blood concentrations; these findings indicate: (1) no increased maternal-fetal cortisol transfer with CMS, (2) cortisol production in CMS fetuses when the HPA-axis is normally inactive, due to early maturation of the fetal HPA-axis. CMS fetuses were better oxygenated, without shift towards acidosis compared to the controls, potentially reflecting adaptation to repeated stress. Hence, CMS enhances maternal-fetal stress transfer by prolonged reduction in UBF and increased fetal HPA responsiveness.

Transfer of maternal psychosocial stress to the fetus

Psychosocial maternal stress experienced during different vulnerable periods throughout gestation is thought to increase the individual's risk to develop neuropsychiatric, cardiovascular and metabolic disease in later life. Cortisol has generally been identified as the major mediator of maternal stress transfer to the fetus. Its lipophilic nature allows a trans-placental passage and thus excessive maternal cortisol could persistently impair the development of the fetal hypothalamic-pituitary-adrenal axis (HPAA). However, cortisol alone cannot fully explain all effects of maternal stress especially during early to mid pregnancy before maturation of the fetal HPAA has even begun and expression of fetal glucocorticoid receptors is limited. This review focuses on mediators of maternal fetal stress transfer that in addition to cortisol have been proposed as transmitters of maternal stress: catecholamines, cytokines, serotonin/tryptophan, reactive-oxygen-species and the maternal microbiota. We propose that the effects of psychosocial maternal stress on fetal development and health and disease in later life are not a consequence of a single pathway but are mediated by multiple stress-transfer mechanisms acting together in a synergistic manner.

Prenatal Maternal Stress and the Risk of Asthma in Children

Emerging evidence indicate that maternal prenatal stress (MPS) can result in a range of long-term adverse effects in the offspring. The underlying mechanism of MPS is not fully understood. However, its complexity is emphasized by the number of purportedly involved pathways namely, placental deregulated metabolism of maternal steroids, impaired maturation of fetal HPA axis, imbalanced efflux of commensal bacteria across the placenta, and skewed immune development toward Th2. Fetal programming probably exerts a pivotal role in the end result of the above pathways through the modulation of gene expression. In this review, we highlight the current knowledge from epidemiological and experimental studies regarding the effects of MPS on asthma development in the offspring.

Cardiac Physiology of Pregnancy

Although the physiology of the heart and vascular system has not changed, there are many things we have learned and are still learning today. Research related to heart adaptations during pregnancy has been performed since the 1930s. Since the mid-1950s, researchers began to look at changes in the maternal cardiovascular system during exercise while pregnant. Research related to exercise during pregnancy and offspring heart development began and has continued since the 1970s. We will review the normal female cardiovascular system adaptations to pregnancy in general. Additionally, topics related to maternal cardiac adaptations to pregnancy during acute exercise, as well as the chronic conditioning response from exercise training will be explored. Since physical activity during pregnancy influences fetal development, the fetal cardiac development will be discussed in regards to acute and chronic maternal exercise. Similarly, the influence of various types of maternal exercise on acute and chronic fetal heart responses will be described. Briefly, the topics related to how and if there is maternal-fetal synchrony will be explained. Lastly, the developmental changes of the fetal cardiovascular system that persist after birth will be explored. Overall, the article will discuss maternal cardiac physiology related to changes with normal pregnancy, and exercise during pregnancy, as well as fetal cardiac physiology related to changes with normal development, and exercise during pregnancy as well as developmental changes in offspring after birth.

Mechanisms underlying the effects of prenatal psychosocial stress on child outcomes: beyond the HPA axis

Accumulating evidence from preclinical and clinical studies indicates that maternal psychosocial stress and anxiety during pregnancy adversely affect child outcomes. However, knowledge on the possible mechanisms underlying these relations is limited. In the present paper, we review the most often proposed mechanism, namely that involving the HPA axis and cortisol, as well as other less well-studied but possibly relevant and complementary mechanisms. We present evidence for a role of the following mechanisms: compromised placental functioning, including the 11β-HSD2 enzyme, increased catecholamines, compromised maternal immune system and intestinal microbiota, and altered health behaviors including eating, sleep, and exercise. The roles of (epi)genetics, the postnatal environment and the fetus are also discussed. We conclude that maternal prenatal psychosocial stress is a complex phenomenon that affects maternal emotions, behavior and physiology in many ways, and may influence the physiology and functioning of the fetus through a network of different pathways. The review concludes with recommendations for future research that helps our understanding of the mechanisms by which maternal prenatal stress exerts its effect on the fetus.

Maternal physical activity mode and fetal heart outcome

BACKGROUND

Maternal leisure-time physical activity (LTPA) improves cardiac autonomic function in the fetus. The specific physical activity attributes (e.g., mode) that produce this benefit are not well understood.

AIM

To determine if more time spent performing non-continuous LTPA during pregnancy is significantly associated with lower fetal heart rate (HR) and increased heart rate variability (HRV).

STUDY DESIGN

This paper presents a retrospective analysis of previously reported data. Fetal magnetocardiograms (MCG) were recorded from 40 pregnant women at 36-wk gestational age.

OUTCOME MEASURES

Metrics of fetal HR and HRV, self-reported min of continuous and non-continuous LTPA performed during the 3-months preceding the 36-wk assessment point and covariates (maternal weight change pre to 36-wk, age, and resting HR and fetal activity state during MCG recordings.

RESULTS

Positive correlations were significant (p<0.05) between min of continuous LTPA, the time domain metrics that describe fetal overall HRV, short-term HRV and a frequency domain metric that reflects vagal activity. Time spent in non-continuous LTPA was positively correlated (p<0.05) with two HRV metrics that reflect fetal overall HRV. In the multiple regression analyses, minutes of non-continuous LTPA remained associated with fetal vagal activity (p<0.05) and the relationships between minutes of non-continuous LTPA and fetal overall HRV (p<0.005) persisted.

CONCLUSION

These data suggest non-continuous physical activity provides unique benefits to the fetal autonomic nervous system that may give the fetus an adaptive advantage. Further studies are needed to understand the physiological mechanisms and long-term health effects of physical activity (both non-continuous and continuous) performed during pregnancy to both women and their offspring.

Prenatal maternal stress exposure and immune function in the offspring

The intra-uterine environment provides the first regulatory connection for the developing fetus and shapes its physiological responses in preparation for postnatal life. Psychological stress acts as a programming determinant by setting functional parameters to abnormal levels, thus inducing postnatal maladaptation. The effects of prenatal maternal stress (PNMS) on the developing immune system have been documented mostly through animal studies, but inconsistent results and methodological differences have hampered the complete understanding of these findings. As the immune system follows a similar ontogenic pattern in all mammals, a translational framework based on the developmental windows of vulnerability proposed by immunotoxicology studies was created to integrate these findings. The objective of this review is to examine the available literature on PNMS and immune function in the offspring through the above framework and gain a better understanding of these results by elucidating the moderating influence of the stressor type, timing and duration, and the offspring species, sex and age at assessment. The evaluation of the literature through this framework showed that the effects of PNMS are parameter specific: the moderating effects of timing in gestation were relevant for lymphocyte population numbers, Natural Killer cell function and mitogen-induced proliferation. The presence of an important and directional sexual dimorphism was evident and the influence of the type or duration of PNMS paralleled that of stress in non-pregnant animals. In conclusion, PNMS is a relevant factor in the programming of immune function. Its consequences may be related to disorders with an important immune component such as allergies.

Fetal stress and programming of hypoxic/ischemic-sensitive phenotype in the neonatal brain: mechanisms and possible interventions

Growing evidence of epidemiological, clinical and experimental studies has clearly shown a close link between adverse in utero environment and the increased risk of neurological, psychological and psychiatric disorders in later life. Fetal stresses, such as hypoxia, malnutrition, and fetal exposure to nicotine, alcohol, cocaine and glucocorticoids may directly or indirectly act at cellular and molecular levels to alter the brain development and result in programming of heightened brain vulnerability to hypoxic-ischemic encephalopathy and the development of neurological diseases in the postnatal life. The underlying mechanisms are not well understood. However, glucocorticoids may play a crucial role in epigenetic programming of neurological disorders of fetal origins. This review summarizes the recent studies about the effects of fetal stress on the abnormal brain development, focusing on the cellular, molecular and epigenetic mechanisms and highlighting the central effects of glucocorticoids on programming of hypoxic-ischemic-sensitive phenotype in the neonatal brain, which may enhance the understanding of brain pathophysiology resulting from fetal stress and help explore potential targets of timely diagnosis, prevention and intervention in neonatal hypoxic-ischemic encephalopathy and other brain disorders.

Glucocorticoids, prenatal stress and the programming of disease

An adverse foetal environment is associated with increased risk of cardiovascular, metabolic, neuroendocrine and psychological disorders in adulthood. Exposure to stress and its glucocorticoid hormone mediators may underpin this association. In humans and in animal models, prenatal stress, excess exogenous glucocorticoids or inhibition of 11β-hydroxysteroid dehydrogenase type 2 (HSD2; the placental barrier to maternal glucocorticoids) reduces birth weight and causes hyperglycemia, hypertension, increased HPA axis reactivity, and increased anxiety-related behaviour. Molecular mechanisms that underlie the 'developmental programming' effects of excess glucocorticoids/prenatal stress include epigenetic changes in target gene promoters. In the case of the intracellular glucocorticoid receptor (GR), this alters tissue-specific GR expression levels, which has persistent and profound effects on glucocorticoid signalling in certain tissues (e.g. brain, liver, and adipose). Crucially, changes in gene expression persist long after the initial challenge, predisposing the individual to disease in later life. Intriguingly, the effects of a challenged pregnancy appear to be transmitted possibly to one or two subsequent generations, suggesting that these epigenetic effects persist.

Resetting the dynamic range of hypothalamic-pituitary-adrenal axis stress responses through pregnancy

The hypothalamic-pituitary-adrenal (HPA) axis plays a key role in the neuroendocrine response to stress. Dynamic changes in HPA axis regulation and hence HPA responsivity occur over the lifetime of an animal. This article focuses on two extremes of the spectrum. The first occurs naturally during pregnancy when stress responses are dampened. The second, at the opposite end of the scale, occurs in offspring of mothers who were exposed to stress during pregnancy and display exaggerated HPA axis stress responses. Reduced glucocorticoid output in response to stress in pregnancy may have important consequences for conserving energy supply to the foetus(es), in modulating immune system adaptations and in protecting against adverse foetal programming by glucocorticoids. Understanding the mechanisms underpinning this adaptation in pregnancy may provide insights for manipulating HPA axis responsiveness in later life, particularly in the context of resetting HPA axis hyperactivity associated with prenatal stress exposure, which may underlie several major pathologies, including cardiovascular disease, diabetes mellitus type 2, obesity, cognitive decline and mood disorders.

Aerobic exercise during pregnancy influences fetal cardiac autonomic control of heart rate and heart rate variability

BACKGROUND

Previous studies using ultrasound technology showed that fetal heart rate (HR) may be responsive to maternal aerobic exercise. Although it is recognized that cardiac autonomic control may be influenced by the intrauterine environment, little is known about how maternal exercise affects fetal heart development.

AIMS

This study tested the hypothesis that regular maternal exercise throughout gestation influences fetal cardiac autonomic control of HR and heart rate variability (HRV) when compared to fetuses of non-exercising women.

STUDY DESIGN

Magnetocardiograms (MCGs) were recorded using a dedicated fetal biomagnetometer at 28, 32 and 36 weeks gestational age (GA) from 26 regularly exercising (>30 min of aerobic exercise, 3x per week) and 35 healthy, non-exercising pregnant women. Fetal MCG was isolated and normal R-peaks were marked to derive fetal HR and HRV in the time and frequency domains. We applied a mixed-effects model to investigate the effects of exercise, GA and fetal activity state.

RESULTS

At 36 weeks GA, during the active fetal state, fetal HR was significantly lower in the exercise group (p=<0.0006). Post-hoc comparisons showed significantly increased HRV in the exercise group during the active fetal state at 36 weeks GA for both time and frequency domain measures.

CONCLUSION

These results indicate that regular maternal exercise throughout gestation results in significantly lower fetal HR and increased HRV.

Maternal and early life stress effects on immune function: relevance to immunotoxicology

Stress is triggered by a variety of unexpected environmental stimuli, such as aggressive behavior, fear, forced physical activity, sudden environmental changes, social isolation or pathological conditions. Stressful experiences during very early life (particularly, maternal stress during fetal ontogeny) can permanently alter the responsiveness of the nervous system, an effect called programming or imprinting. Programming affects the hypothalamic-pituitary-adrenocortical (HPA) axis, brain neurotransmitter systems, sympathetic nervous system (SNS), and the cognitive abilities of the offspring, which can alter neural regulation of immune function. Prenatal or early life stress may contribute to the maladaptive immune responses to stress that occur later in life. This review focuses on the effect of maternal and early life stress on immune function in the offspring across life span. It highlights potential mechanisms by which prenatal stress impacts immune functions over life span. The literature discussed in this review suggests that psychosocial stress during pre- and early postnatal life may increase the vulnerability of infants to the effects of immunotoxicants or immune-mediated diseases, with long-term consequences. Neural-immune interactions may provide an indirect route through which immunotoxicants affect the developing immune system. A developmental approach to understanding how immunotoxicants interact with maternal and early life stress-induced changes in immunity is needed, because as the body changes physiologically across life span so do the effects of stress and immunotoxicants. In early and late life, the immune system is more vulnerable to the effects of stress. Stress can mimic the effects of aging and exacerbate age-related changes in immune function. This is important because immune dysregulation in the elderly is more frequently and seriously associated with clinical impairment and death. Aging, exposure to teratogens, and psychological stress interact to increase vulnerability and put the elderly at the greatest risk for disease.

Common problems in critically ill obstetric patients, with an emphasis on pharmacotherapy

Pharmacological treatment of critically ill obstetric patients can be especially challenging due to the complexity of caring for 2 patients, with a paucity of research to support practice. This review will provide practitioners with primary recommendations for management of the critical illnesses most commonly encountered in pregnancy and will discuss the scientific and clinical merit of these recommendations.

Prenatal stress, fetal imprinting and immunity

A comprehensive number of epidemiological and animal studies suggests that prenatal and early life events are important determinants for disorders later in life. Among them, prenatal stress (i.e. stress experienced by the pregnant mother with impact on the fetal ontogeny) has programming effects on the hypothalamic-pituitary-adrenocortical axis, brain neurotransmitter systems and cognitive abilities of the offspring. This review focuses on the impact of maternal stress during gestation on the immune function in the offspring. It compares results from different animal species and highlights potential mechanisms for the immune effects of prenatal stress, including maternal glucocorticoids and placental functions. The existence of possible windows of increased vulnerability of the immune system to prenatal stress during gestation is discussed. Several gaps in the present knowledge are pointed out, especially concerning the time when prenatal stress effects are expressed during postnatal life, why this expression is delayed after birth and whether prenatal stress predisposes to immune-related pathologies later in life.

Management of glaucoma in pregnancy and lactation

A 30-year-old pregnant woman with glaucoma is presented. The management of her case is used as a basis for a discussion of the use of glaucoma medications, including newer formulations, during pregnancy and lactation.

The extraneuronal monoamine transporter Slc22a3/Orct3 co-localizes with the Maoa metabolizing enzyme in mouse placenta

Monoamine clearance is a combined function of uptake mechanisms in the plasma membrane with intracellular metabolizing enzymes. Two different uptake mechanisms have been described. Uptake(1) is located in presynaptic neurones, whereas uptake(2) is extraneuronal. Recently, the Slc22a3/Orct3 gene was identified as the extraneuronal monoamine transporter. In mouse embryonic development Orct3 expression is restricted to the placenta, which is also a site of expression of neuronal transporters. We have used RNA blots and in situ hybridization to examine the expression of Orct3 and other members of the monoamine uptake and metabolizing pathways in mouse placenta. The results show that Orct3 expression overlaps that of the monoamine metabolizing enzyme Maoa in the labyrinth layer of the placenta with an expression pattern distinct from that of the neuronal transporters Slc6a2/Net and Slc6a4/Sert.

Cocaine-induced alterations in the density of monoaminergic receptors in the embryonic guinea pig cerebral wall

Quantitative receptor autoradiography was used to examine the effect of chronic cocaine exposure on the density of alpha1-, alpha2- and beta-adrenergic, 5-HT1A- and 5-HT2-serotonergic, and D1- and D2-dopaminergic receptors in the fetal guinea pig cerebral wall which contained forming motor area of the cerebral cortex. The pregnant guinea pig received two daily subcutaneous injections of 20 mg/kg cocaine beginning on the 20th day of pregnancy (E20). The control animals received injections of equivalent volume of saline. The receptor densities were examined between days 5-30 of the treatment, which corresponds to E25-E50. By the fifth day of treatment (E25), cocaine produced downregulation of all receptors studied throughout the entire depth of the fetal cerebral wall. More extended treatment, however, resulted in recovery of receptor levels. Finally, from days 20-30 of treatment (E40-E50) there was a significant upregulation of noradrenergic and dopaminergic receptor sites. These findings demonstrate that exposure to cocaine in utero can influence adrenergic, serotonergic, and dopaminergic receptors in the embryonic cerebral wall, which may lead to alteration in corticogenesis. Furthermore, the present study reveals that, in the course of chronic treatment, cocaine may completely reverse its receptor regulatory activity in the fetal brain.

Physical conditioning effects on fetal heart rate responses to graded maternal exercise

PURPOSE

This study examined the effects of advancing gestational age and maternal aerobic conditioning (stationary cycling) on fetal heart rate (FHR) responses to strenuous non-steady-state maternal exercise.

METHODS

Subjects chose to participate in either an exercise group (EG) or control group (CG). Fourteen healthy, previously sedentary pregnant women participated in the exercise group, and six pregnant controls remained sedentary. Stationary cycling (heart rate target: 145 beats x min(-1)) was performed 3 d x wk(-1) by the exercised group. Exercise duration was increased from 14 to 25 min x session(-1) during the second trimester and was maintained at 25 min x session(-1) throughout the third trimester. FHR was monitored before, during, and after a progressive submaximal cycle ergometer test (peak heart rate = 170 beats x min(-1)) performed at approximately 27 and 37 wk gestation.

RESULTS

Mean FHR increased significantly (P < 0.05) during exercise, followed by a modest suppression and then a delayed rise during the recovery period at both observation times. Fetal bradycardia was not observed in any of the exercise tests. Effects of advancing gestational age included a lower FHR baseline both at rest and in response to maternal exercise and a lower incidence of exercise-induced tachycardia. Maternal physical conditioning did not significantly alter FHR response to maternal exercise.

CONCLUSION

Our results support the hypothesis that FHR responses to strenuous exercise are altered by advancing gestational age and a brief progressive exercise test terminated at a maternal heart rate of 170 beats x min(-1) does not induce fetal distress during a healthy pregnancy.

Human fetal and maternal noradrenaline responses to invasive procedures

Fetal and maternal plasma noradrenaline responses to invasive procedures were determined in pregnancies of 18 to 37 wk gestation. Fetal umbilical venous blood sampling was performed either from the placental cord insertion, which is not innervated, or the intrahepatic vein, which is innervated, and thus may be more stressful for the fetus. Samples from diagnostic procedures, as well as from transfusion procedures, were compared between the two sites. Fetal plasma levels were significantly elevated in blood samples obtained from the intrahepatic vein compared with those from the placental cord insertion during diagnostic procedures [p < 0.05, geometric means and 95% confidence intervals (CI) were 0.67 nmol/L (0.43-1.04) and 0.36 nmol/L (0.25-0.54), respectively]. Plasma levels in samples taken before transfusion from the intrahepatic vein were also significantly higher than those from the placental cord insertion. After transfusion, there was a significant rise in fetal plasma noradrenaline levels at both sites; however, after transfusion through the intrahepatic vein, the rise was substantially greater than after transfusion through the placental cord insertion (p < 0.05, change, mean deltaNA, and 95% CI were 0.67 (0.37-1.22), and 0.20 (0.12-0.33), respectively). The deltaNA was significantly associated with the duration of the stimulus (the time the needle remained in situ) (p = 0.05, adjusted R2 = 0.48) and with gestational age. Maternal levels rose substantially and equally after transfusions at either site (mean deltaNA and 95% CI, 6.46 nmol/L, 1.74 to 11.18 and 9.49 nmol/L, 6.24 to 12.75 for the intrahepatic vein and placental cord insertion groups, respectively). There was no significant correlation between baseline fetal and maternal levels (r = 0.08, n = 41) or between deltaNA pre- and posttransfusion maternal and fetal values in either group. These results indicate that the fetus is capable of mounting an independent noradrenaline stress response to a needle transgressing its trunk from 18 wk gestation. The effect was observable in samples taken at a mean of 5.6 min after needling. The lack of correlation between maternal and fetal levels suggests that virtually no noradrenaline crosses the placenta directly, and that the observed fetal responses are not due to direct transport from the mother.

Left ventricular norepinephrine and epinephrine kinetics at birth in lambs

Little is known about the changes in the left ventricular (LV) kinetics of the catecholamines norepinephrine and epinephrine occurring at birth and their relationship to perinatal alterations in LV function and whole-body catecholamine kinetics. To address this issue, whole-body and LV catecholamine kinetics (radiotracer dilution methodology) and fetal LV output and myocardial blood flow (radioactive microspheres) were measured in chronically instrumented near-term fetuses and in the same animals 1 and 4 hours after birth. Between fetal and 1-hour lambs, LV external work increased 115% (P<.005); carotid arterial plasma norepinephrine concentration, 148% (P<.01); carotid arterial plasma epinephrine concentration, 546% (P<.005); LV norepinephrine spillover, a measure of LV sympathetic activity, 4.1-fold (P<.005); LV epinephrine spillover, 3-fold (P<.05); total-body spillover of norepinephrine, 52% (P<.025); and total-body spillover of epinephrine, 460% (P<.005). Arterial catecholamine concentrations and total-body catecholamine spillovers were unchanged between 1- and 4-hour lambs, but LV external work fell (P<.05) to a level still 77% greater than in fetal lambs (P<.005); LV norepinephrine spillover returned to near-fetal levels, and LV epinephrine spillover became undetectable. These results suggest that (1) a transient increase in LV sympathetic activity occurs at birth and may contribute to the immediate postnatal augmentation of LV performance, (2) organ differences in the pattern of sympathetic activation occur at birth, and (3) birth-related increases in LV sympathetic activity are accompanied by release of epinephrine from the heart.

Noradrenaline is essential for mouse fetal development

Catecholamines such as noradrenaline and adrenaline have been implicated in numerous physiological processes but, although catecholamine synthesis begins at mid-gestation, previous studies have provided little evidence for any role in early development. Furthermore, there are several case reports of humans with noradrenaline deficiency. To investigate this, we use gene targeting to produce mice lacking dopamine beta-hydroxylase and therefore unable to synthesize noradrenaline or adrenaline. We report here that in heterozygous mothers, most homozygous embryos died in utero, and only about 5% reached adulthood. Survival probably depends on catecholamine transfer across the placenta because, in homozygous mothers, all embryos die in utero. Mortality was due to lack of noradrenaline in utero because it could be prevented by treatment with dihydroxyphenylserine, a precursor that can be converted to noradrenaline in the absence of dopamine beta-hydroxylase. Mutant embryos had a histological phenotype similar to that of embryos deficient in tyrosine hydroxylase, suggesting that death might be due to cardiovascular failure.

Human placenta: a direct target for cocaine action

Use of cocaine during pregnancy is known to have harmful effects on the mother and her fetus. Currently available models describing the pathogenesis of these effects focus on the involvement of cocaine target systems, primarily the noradrenaline transporter, in the mother and the fetus. The placenta which lies between the mother and the fetus is considered only as a 'silent observer' in the whole process of cocaine-induced complications during pregnancy. Recent studies have, however, shown that the placenta expresses several cocaine target proteins such as the noradrenaline transporter, the serotonin transporter, and the sigma receptor. The functions of these proteins are significantly impaired in the presence of cocaine at concentrations known to exist in the plasma of cocaine users. These studies clearly show that the placenta itself is a direct target for cocaine action and that interaction of cocaine with its target proteins in the placenta plays an important role in the pathogenesis of cocaine-induced complications in the mother and her developing fetus.

Cloning and characterization of human placental catechol-O-methyltransferase cDNA

Catechol-O-methyltransferase (COMT) cDNA clones were isolated from a human placental cDNA library using synthetic oligonucleotides as probes. All four positive clones isolated contained an open reading frame, which potentially coded for a 24.4-kD polypeptide, presumably corresponding to the cytoplasmic form of the COMT (S-COMT). In addition to the S-COMT sequences, two of the clones carried extensions in the 5' end, which potentially coded for a 50-amino-acid peptide extending the S-COMT reading frame. This sequence contained a stretch of signal sequence-like hydrophobic amino acids in its amino terminus. The deduced human COMT polypeptide had 80% similarity with the previously characterized rat COMT. Expression of one of the cDNA clones in human K-562 cells resulted in cell clones with 3- to 10-fold increased COMT activity. Cell-free translation of transcripts synthesized in vitro from one of the short cDNAs yielded a 26-kD product, similar in size to human S-COMT. Translation of transcripts from one of the long cDNAs gave 30-kD and 26-kD polypeptides, suggesting translation initiation from two different AUG initiation codons. The 30-kD protein, but not the 25-kD protein, associated with microsomal membranes in translation lysates. A potential polyadenylation signal AATTAA was detected in the 3' ends of two of the clones 265 nucleotides downstream from the COMT translation termination codon. RNA blotting on human placental RNA revealed a 1.5-kb-long COMT-specific transcript. DNA analysis suggested that human, as well as rat, canine and monkey cells have one gene for COMT.

Effect of oestrogens and progesterone on the metabolic inactivation of noradrenaline in the human placenta

The enzymatic inactivation of noradrenaline was investigated in 25 fresh human placentae in vitro. Oxidative deamination by monoamine oxidase (MAO) was greater than enzymic O-methylation by catechol-O-methyltransferase (COMT). The addition of oestriol (E3) or progesterone to the organ bath significantly decreased (P less than 0.001) the activity of placental MAO. Oestrone (E1) and oestradiol (E2) showed no inhibitory effect. In addition, E3 significantly inhibited the activity of COMT (P less than 0.001), whereas oestrone and oestradiol had no effect on COMT activity. COMT was also inhibited by progesterone (P less than 0.05). The decrease in enzymic inactivation of noradrenaline caused by oestriol and progesterone suggests an activated adrenoceptor function.

Catecholamines in arterial and venous umbilical blood: placental extraction, correlation with fetal hypoxia, and transcutaneous partial oxygen tension

In 34 parturient women the levels of free epinephrine (E), norepinephrine (NE), and dopamine (D) were determined by a radioenzymatic method using maternal venous and umbilical arterial and venous blood. The study was conducted to investigate the relationship between fetal catecholamines and hypoxia, fetal heart rate (FHR), and transcutaneous pO2 (tcpO2). The placental catecholamine extraction rates were also calculated. Results The NE concentrations (10,200 pg/ml) and the E concentrations (1,120 pg/ml) in the fetal arterial blood were highly elevated with mean values increased 4-fold over umbilical vein values. Compared with the maternal venous blood, NE values were increased 20-fold, and E values 10-fold. Free D concentrations in fetal arterial blood (130 pg/ml) had risen 2.5-fold over maternal levels. These results suggest that the catecholamines measured in cord blood are of fetal origin and that the placenta has a high capacity for inactivation of free catecholamines. The placental extraction rate is 77 +/- 14% for NE, 76 +/- 16% for E, and 33 +/- 25% for D. The placental extraction rates for E and NE were virtually identical; in agreement with morphological studies they demonstrated absence of sympathetic innervation on the fetal side of the placenta. Highly significant correlations were found between fetal arterial NE concentrations and the 1-minute APGAR score, pH and base deficit in the umbilical artery and alterations of the FHR (deceleration area, baseline FHR). Further analysis of FHR alterations reveals that an increase in deceleration area without tachycardia is not correlated with an increase of fetal arterial NE concentration. A significant rise in NE was only found with additional tachycardia which is often associated with a loss of oscillation amplitude. Fetal arterial E concentrations were found to correlate with the fetal parameters indicating increased adrenal secretion of the hormone during fetal stress. However, correlation coefficients were lower than those obtained for NE. A significant effect of fetal hypoxia on arterial and venous D levels could not be demonstrated. Fetal tcpO2 varies between 0-25 mm Hg during the last two hours before delivery. In most cases tcpO2 was lower than the arterial pO2. Besides epidermal thickness and artifacts, skin perfusion is a major factor influencing the tcpO2 (transcutaneous arterial pO2 difference). Vasoconstriction of the cutaneous vessels induced by increased NE secretion during hypoxia may obviously produce a fall in tcpO2.(ABSTRACT TRUNCATED AT 400 WORDS)

Catecholamine physiology in the ovine fetus. I. Gestational age variation in basal plasma concentrations

Fifty-five ewes with chronically catheterized singleton gestations were studied to assess changes in basal concentrations of fetal catecholamines with increasing gestational age. All pregnancies were time dated, and measurements of catecholamines were conducted at least 5 days after placement of fetal catheters when fetal metabolic parameters had normalized. Plasma concentrations of catecholamines were measured by radioenzymatic assay. Additionally, fetal heart rate (FHR) and corrected mean blood pressure were analyzed in 32 of the fetuses for correlation with plasma levels of catecholamines. Multiple regression analysis revealed significant inverse correlations of fetal plasma concentrations of catecholamines with gestational age, as follows: norepinephrine (p less than 0.001), epinephrine (p less than 0.05), and dopamine (p less than 0.01). FHR correlated inversely with gestational age (p less than 0.001) and positively with circulating levels of norepinephrine (p less than 0.001).

Transfer and metabolism of norepinephrine studied from maternal-to-fetal and fetal-to-maternal sides in the in vitro perfused human placental lobe

An in vitro system for the dual perfusion of an isolated lobe of human placenta was used to study transfer and metabolism of 3H-labeled norepinephrine at two different concentrations. At 39 mumol/L, the transfer of total radioactivity from the maternal to the fetal side was 11.60% +/- 0.60% and significantly higher (p less than 0.05) than that in the opposite direction (6.50% +/- 0.37%). In both directions almost 50% of tritium was transferred as norepinephrine while the rest was metabolized and appeared on the other side as normetanephrine, dihydroxymandelic acid, and vanillylmandelic acid. When a reduced concentration (870 nmol/L) was infused into either the maternal or the fetal compartment, transfer and metabolism were similar to those determined before. Analysis of the tissue showed 50% of total radioactivity as normetanephrine, dihydroxymandelic acid, and vanillylmandelic acid and 17% as conjugates. Inclusion of the monoamine oxidase inhibitor clorgyline in the perfusate significantly reduced fetal-to-maternal transfer but not transfer in the reverse direction. In addition, inhibition of placental monoamine oxidase resulted in a considerable reduction in dihydroxymandelic acid and vanillylmandelic acid while the normetanephrine fraction increased. Norepinephrine significantly increased glucose utilization and lactate production. A possible physiologic role of norepinephrine transferred from the fetal into the maternal circulation during labor is discussed.

Subhourly variability of circulating norepinephrine and epinephrine in the pregnant ewe and fetal and newborn lamb

Circulating norepinephrine and epinephrine were determined nine times over a 1-hour period in chronically instrumented ewes (n = 4), their fetuses (n = 4), and lambs (n = 4). In an apparent resting state, assessed by subjective and biophysical parameters, marked fluctuations were demonstrated in the mean norepinephrine and epinephrine values between animals and in the range of the concentrations of each individual animal. The significance of the fluctuations in resting plasma norepinephrine and epinephrine concentrations is discussed.

Fetal catecholamines

Experimental data from fetal human and animal research suggest that the fetal sympathoadrenal system, composed of the adrenal medulla, sympathetic neurons, and extra-adrenal chromaffin tissue functions from early fetal life to maintain fetal homeostasis. The extra-adrenal chromaffin tissue undergoes maturation at 9 to 11 weeks of gestation, whereas the adrenal medulla and sympathetic nervous system mature later in fetal life. The fetal catecholamine response to hypoxia, mediated predominantly by norepinephrine, is an important component of the fetal cardiovascular response to hypoxia, i.e., through alpha-receptor stimulation, fetal cardiac output redistribution occurs. Fetal catecholamine secretion in response to substrate availability, through alpha- and beta-receptor stimulation, provide a mechanism by which the fetus can utilize its own substrate stores. Pulmonary beta-receptor stimulation by catecholamines has been demonstrated to increase lecithin synthesis, increase surfactant secretion, and decrease lung fluid production near term. beta-Receptor stimulation has also been demonstrated to have trophic effects on the development of thermogenic brown adipose tissue. Although the exact stimulus for the initiation of parturition in the primate is unknown, fetal catecholamines, through direct myometrial alpha-adrenergic or dopaminergic receptor stimulation and/or through the stimulation of prostaglandin production, have the potential of facilitating the onset of parturition.

Placental monoamine oxidase content and inhibition: effect of enzyme inhibition on maternofetal transfer of noradrenaline (norepinephrine) in the human placenta in vitro

The effect of monoamine oxidase (MAO) inhibition on maternofetal transfer of noradrenaline (NA) has been investigated in vitro using dual perfusion of isolated human placental lobules. As a first step, placental MAO content and its sensitivity to inhibition by pargyline were assessed in incubation studies of homogenates as well as during perfusion, taking rat liver as reference. Our results show that the human placenta, though it contains as great an enzyme activity as rat liver, was less sensitive to inhibition by pargyline than the latter. MAO inhibition by pargyline significantly reduced the NA clearance from maternal to fetal circulation. Thus the proportion of unmetabolized NA radioactivity in fetal venous samples decreased significantly after pargyline treatment. A concomitant rise in the proportion of mainly O-methylated metabolites was also observed. We speculate that the apparent activation of catechol-O-methyl transferase pathway, observed in our studies on MAO inhibition, may play an important role in limiting NA transfer towards the fetus in toxaemic pregnancies associated with the reduction in placental MAO.

Metabolism of 3H-dopamine by human chorioamnion in vitro

Previous investigation has demonstrated biologically significant concentrations of catecholamines in amniotic fluid, which increase with gestation. The half life, metabolic clearance rate, and metabolic fate of these hormones in the amniotic compartment are yet to be established. This study was undertaken to demonstrate the ability of human chorioamnion to metabolize dopamine in vitro. Incubation experiments demonstrated that 3H-dopamine is rapidly metabolized to dihydroxyphenylacetic acid, 3-methoxy, 4-hydroxyphenylacetic acid, and 3-methoxy, 4-hydroxyphenylethanol-all products of monoamine oxidase. No significant 3-methoxytyramine, a catechol-o-methyltransferase product, was observed. Incubation experiments with pargyline, a monoamine oxidase inhibitor, resulted in significant reduction in 3H-dopamine metabolism. Catecholamines and their interaction with prostaglandin synthesis have been theorized to be a fetal signal for the initiation of parturition. The ability of chorioamnion to metabolize catecholamine could, therefore, provide another control mechanism by which fetal catecholamines are modulated.

Circumstances influencing umbilical-cord plasma catecholamines at delivery

Blood gases and plasma catecholamines were measured in umbilical arterial and venous blood samples after delivery. In all cases umbilical arterial noradrenaline concentrations were higher than venous levels. The lowest concentrations of noradrenaline were found after elective caesarean section. Vaginal delivery, particularly when accompanied by instrumental manipulation, was associated with significantly higher concentrations of arterial noradrenaline. High concentrations of catecholamines were commonly recorded in those deliveries showing evidence of acid-base disturbance. Noradrenaline was the predominant catecholamine in all cases. A linear relation was demonstrated between arterial noradrenaline and arteriovenous noradrenaline difference.

The fetal and maternal catecholamine response to insulin-induced hypoglycemia in the rat

This study was undertaken to evaluate the catecholamine response of the fetal rat to insulin-induced hypoglycemia in the mother. Twenty-four Sprague-Dawley rats at day 21 of gestation were used. Hypoglycemia was induced with regular insulin; then at timed intervals, the rats were anesthetized with pentobarbital. When the rats were completely unresponsive, the abdomen was opened, the fetuses were exteriorized, and fetal blood was obtained by sectioning the axillary vessels. Maternal blood was obtained from the vena cava. Plasma glucose was measured by the glucose oxidase technique. Norepinephrine, epinephrine, and dopamine were measured by radioenzymatic assay. Maternal animals demonstrated a fall in glucose to a nadir of 23 +/- 0.7 mg/dl (mean +/- SEM) and a significant rise in plasma epinephrine to a maximum of 2,548.0 +/- 1,071.2 pg/ml. Fetal glucose fell to a nadir of 23.8 +/- 3.3 mg/dl (mean +/- SEM) and fetal catecholamines demonstrated a rapid significant rise: norepinephrine rose to a maximum of 5,077.3 +/- 932.6 pg/ml; epinephrine rose to a maximum of 4,295.8 +/- 538.9 pg/ml; dopamine rose to a maximum of 869 +/- 203.3 pg/ml. The fetal correlation coefficients were r = -0.56 (p less than 0.01) for plasma glucose compared to norepinephrine and r = -0.58 (p less than 0.01) for plasma glucose compared to epinephrine. The maternal correlation coefficient for plasma glucose compared to epinephrine was r = -0.54 (p less than 0.01). These data demonstrate that the near-term fetal rat is able to respond significantly to hypoglycemia with a rapid output of catecholamines.

An increase in catecholamines and metabolites in the amniotic fluid compartment from middle to late gestation

By means of a modified radioenzymatic assay, simultaneous determinations of the parent catecholamines, epinephrine (E), norepinephrine (NE), and dopamine (DA), and their deaminated metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylglycol (DOPEG), were made in amniotic fluid obtained during the second (N = 44) and third (N = 20) trimesters of normal pregnancies. Significant positive correlations were noted between gestational age and concentrations of E, NE, DA, DOPAC, and DOPEG in amniotic fluid. These findings provide evidence of progressive fetal adrenergic maturation through pregnancy. In addition, our data suggest a parallel maturational event in the central nervous and peripheral catecholamine systems of the fetus, since DOPAC and DOPEG are more representative of catecholamine neuronal activity in the brain.

Plasma catecholamine concentrations in infants at birth and during the first 48 hours of life

A radioenzymatic assay was used to measure plasma concentrations of the catecholamines, norepinephrine, and epinephrine in the perinatal period. Samples were obtained at birth from the umbilical artery and vein of infants born by vaginal and by cesarean section delivery; from peripheral venous samples of normal infants during the first 48 hours of life; and from peripheral venous samples of mothers prior to delivery. Concentrations of NE and E were elevated in umbilical samples, with umbilical artery levels exceeding umbilical venous concentrations. Umbilical plasma CAT concentrations were similar in vaginal and cesarean section delivered infants. Plasma concentrations of NE consistently predominated over E in all samples from neonates. Plasma CAT concentrations rapidly fell from cord levels within 15 minutes of delivery and remained at a lower plateau during the first three hours of life. By 12 hours of age plasma CAT concentrations fell to the levels of supine adult resting concentrations. Maternal plasma CAT concentration prior to delivery demonstrated a predominance of E over NE. These elevations of plasma CAT in the early neonatal period may play a rola in nonshivering heat production as well as in cardiovascular alterations associated with birth.