Amniotic fluid catecholamine metabolites in maternal smoking

Maternal and fetal metabonomic alterations in prenatal nicotine exposure-induced rat intrauterine growth retardation

Prenatal nicotine exposure causes adverse birth outcome. However, the corresponding metabonomic alterations and underlying mechanisms of nicotine-induced developmental toxicity remain unclear. The aims of this study were to characterize the metabolic alterations in biofluids in nicotine-induced intrauterine growth retardation (IUGR) rat model. In the present study, pregnant Wistar rats were intragastrically administered with different doses of nicotine (0.5, 1.0 and 2.0 mg/kg d) from gestational day (GD) 11-20. The metabolic profiles of the biofluids, including maternal plasma, fetal plasma and amniotic fluid, were analyzed using (1)H nuclear magnetic resonance (NMR)-based metabonomic techniques. Prenatal nicotine exposure caused noticeably lower body weights, higher IUGR rates of fetal rats, and elevated maternal and fetal corticosterone (CORT) levels compared to the controls. The correlation analysis among maternal, fetal serum CORT levels and fetal bodyweight suggested that the levels of maternal and fetal serum CORT presented a positive correlation (r=0.356, n=32, P<0.05), while there was a negative correlation between fetal (r=-0.639, n=32, P<0.01) and maternal (r=-0.530, n=32, P<0.01) serum CORT level and fetal bodyweight. The fetal metabonome alterations included the stimulation of lipogenesis and the decreased levels of glucose and amino acids. The maternal metabonome alterations involved the enhanced blood glucose levels, fatty acid oxygenolysis, proteolysis and amino acid accumulation. These results suggested that prenatal nicotine exposure is associated with an altered maternal and fetal metabonome, which may be related to maternal increased glucocorticoid level induced by nicotine.

The fetal cardiovascular response to increased placental vascular impedance to flow determined with 4-dimensional ultrasound using spatiotemporal image correlation and virtual organ computer-aided analysis

OBJECTIVE

We sought to determine if increased placental vascular impedance to flow is associated with changes in fetal cardiac function using spatiotemporal image correlation and virtual organ computer-aided analysis.

STUDY DESIGN

A cross-sectional study was performed in fetuses with umbilical artery pulsatility index >95th percentile (abnormal [ABN]). Ventricular volume (end-systole, end-diastole), stroke volume, cardiac output (CO), adjusted CO, and ejection fraction were compared to those of 184 normal fetuses.

RESULTS

A total of 34 fetuses were evaluated at a median gestational age of 28.3 (range, 20.6-36.9) weeks. Mean ventricular volumes were lower for ABN than normal cases (end-systole, end-diastole) with a proportionally greater decrease for left ventricular volume (vs right). Mean left and right stroke volume, CO, and adjusted CO were lower for ABN (vs normal) cases. Right ventricular volume, stroke volume, CO, and adjusted CO exceeded the left in ABN fetuses. Mean ejection fraction was greater for ABN than normal cases. Median left ejection fraction was greater (vs right) in ABN fetuses.

CONCLUSION

Increased placental vascular impedance to flow is associated with changes in fetal cardiac function.

Risks and benefits of nicotine to aid smoking cessation in pregnancy

Cigarette smoking during pregnancy is the single largest modifiable risk for pregnancy-related morbidity and mortality in the US. Addiction to nicotine prevents many pregnant women who wish to quit smoking from doing so. The safety and efficacy of nicotine replacement therapy (NRT) for smoking cessation during pregnancy have not been well studied. Nicotine is classified by the US Food and Drug Administration as a Pregnancy Category D drug. Animal studies indicate that nicotine adversely affects the developing fetal CNS, and nicotine effects on the brain may be involved in the pathophysiology of sudden infant death syndrome (SIDS). It has been assumed that the cardiovascular effects of nicotine resulting in reduced blood flow to the placenta (uteroplacental insufficiency) is the predominant mechanism of the reproductive toxicity of cigarette smoking during pregnancy. Short term high doses of nicotine in pregnant animals do adversely affect the maternal and fetal cardiovascular systems. However, studies of the acute effects of NRT in pregnant humans indicate that nicotine alone has minimal effects upon the maternal and fetal cardiovascular systems. Cigarette smoking delivers thousands of chemicals, some of which are well documented reproductive toxins (e.g. carbon monoxide and lead). A myriad of cellular and molecular biological abnormalities have been documented in placentas, fetuses, and newborns of pregnant women who smoke. The cumulative abnormalities produced by the various toxins in cigarette smoke are probably responsible for the numerous adverse reproductive outcomes associated with smoking. It is doubtful that the reproductive toxicity of cigarette smoking is primarily related to nicotine. We recommend the following. Efficacy trials of NRT as adjunctive therapy for smoking cessation during pregnancy should be conducted. The initial dose of nicotine in NRT should be similar to the dose of nicotine that the pregnant woman received from smoking. Intermittent-use formulations of NRT (gum, spray, inhaler) are preferred because the total dose of nicotine delivered to the fetus will be less than with continuous-use formulations (transdermal patch). A national registry for NRT use during pregnancy should be created to prospectively collect obstetrical outcome data from NRT efficacy trials and from individual use. The goal of this registry would be to determine the safety of NRT use during pregnancy, especially with respect to uncommon outcomes such as placental abruption. Finally, our review of the data indicate that minimal amounts of nicotine are excreted into breast milk and that NRT can be safely used by breast-feeding mothers.

Smoking during pregnancy: foetal growth retardation and other risks for the newborn

In spite of the well-known effect of tobacco on embryo growth retardation, of the higher perinatal mortality of the offspring of smoking mothers, and of the dependence of perinatal mortality risk on small birth weight, it has consistently been found that small infants of smoking mothers have lower mortality rates than small infants of non-smoking mothers. This problem was studied on the perinatal database of a hospital, using adverse outcomes (death or Apgar score <7 at the 10th minute of life) as endpoints rather than perinatal or foetal mortality. A stochastic model constructed to account for cause-effect relations demonstrated that tobacco influences weight and mortality by independent pathways. Furthermore, this model shed some light on the non-tobacco determinants of small birth weight and neonatal morbidity. The method undertaken, based on the use of latent variables, had the advantage of analysing the prevalence, consequences and interactions of some risk factors without identifying them.

Nicotine transport in a human choriocarcinoma cell line (JAR)

Smoking is a major health problem in pregnancy resulting in intrauterine growth retardation and birth complications. Nicotine, a toxic component of cigarette smoke, interferes with amino acid transport in the placenta and stimulates catecholamine release resulting in uteroplacental vasoconstriction. Transplacental transport of nicotine may be an important determinant of placental and fetal exposure. Our aim was to determine the mechanism of nicotine transport in the human choriocarcinoma cell line, JAR, as a model for the placenta. JAR cells were subcultured in 12-well plates following trypsinization at a seeding density of 0.5 x 10(6) cells/well (1.3 x 10(5) cells/cm2). Uptake studies of [3H]nicotine were carried out in JAR cell monolayers on day 2 after plating. [3H]Nicotine uptake was saturable (Km 156 microM), sensitive to temperature, and inhibited by unlabeled nicotine and various organic cations including mecamylamine and quinidine, but not by guanidine, tetraethylammonium (TEA), or neurotransmitters. Counterflux of [3H]nicotine uptake was produced by unlabeled nicotine and mecamylamine but not by cotinine or acetylcholine, consistent with a carrier-mediated transport process. The uptake could be driven by an inside-negative membrane potential or by an outwardly directed pH gradient. This is the first demonstration of a carrier-mediated transport mechanism for nicotine in a human cell line. This transport mechanism may have implications to the disposition of nicotine in the human placenta.

Cerebrospinal fluid neuroendocrinology of alcohol misusers

Cerebrospinal fluid (CSF) neurohumors reflect central nervous system physiology in a way that peripheral indices can not. We reviewed clinical studies of CSF biogenic amines and neurohormones in alcohol misusers during various stages of withdrawal or abstinence and found them difficult to compare because of highly variable experimental methods, reliance on single time collections (lumbar punctures) that fail to control for potential stress-induced effects of the procedure, lack of control for tobacco use, and a paucity of non-alcoholmisusing controls. However, taken together, the data thus far show that a variety of neuroactive substances are reduced in concentration in the CSF of some alcohol misusers. Low CSF levels of corticotropinreleasing hormone, beta-endorphin, norepinephrine, diazepam-binding inhibitor, 5-hydroxyindoleacetic acid and somatostatin have all been reported. Whether the decreased CSF levels of these neurohormones and neurotransmitters are a cause or consequence of alcoholism has not been determined. In fact, further studies using serial or continuous CSF sampling techniques with homogeneous, better-characterized patients and normal volunteers are still needed to establish the precise CSF neurochemical abnormalities in alcohol misusers.

Meconium analysis to assess fetal exposure to nicotine by active and passive maternal smoking

We measured nicotine metabolites (cotinine and trans-3'-hydroxycotinine) in meconium of infants of passive or active smokers as a direct marker of fetal exposure to tobacco smoke. Meconium was collected from 55 infants whose mothers were nonsmokers, passive smokers, or light or heavy active smokers. Nicotine metabolite concentration (NMC) in meconium was analyzed by radioimmunoassay and gas chromatography-mass spectrometry. Radioimmunoassay showed the following mean meconium NMCs (in nanograms per milliliter); nonsmoker, 10.9; passive smoker, 31.6; light active smoker; 34.7, and heavy active smoker, 54.6. Analysis of available samples by gas chromatography-mass spectrometry confirmed the presence of cotinine. Correlation between meconium NMC and the degree of maternal smoking was 0.54 (p < 0.001). Meconium NMCs in infants of passive and active smokers were significantly higher than in those of nonsmokers (p < 0.05). Meconium NMC in passive smokers was not significantly different from that in light active smokers (p > 0.05). Thus exposure of the fetus to tobacco smoke is substantial, even by passive maternal smoking. Meconium analysis for nicotine metabolites may be useful for clinical and research purposes.

Acute intrauterine hypoxia increases amniotic fluid prostaglandin F metabolites in the pregnant sheep

OBJECTIVE

Amniotic fluid infection promotes cytokine release, prostaglandin production, and premature labor. In several tissues local hypoxia also activates the secretion of cytokines. Many patients initially seen in premature labor carry small-for-gestational-age fetuses, a condition associated with intrauterine hypoxia. The purpose of our study was to determine whether a reduction in placental blood flow and subsequent acute hypoxia affects prostaglandin secretion by the placenta.

STUDY DESIGN

We chronically catheterized six pregnant sheep at 120 days of gestation. We placed catheters in the maternal and fetal femoral arteries and in the amniotic fluid cavity. A flow probe and snare were placed around the common uterine artery.

RESULTS

A 30-minute uterine circulation occlusion of 30% of its control value produced an increase in prostaglandin F metabolite from 790 +/- 157 to 944 +/- 184 pg/ml within 10 minutes (p < 0.01). Additional uterine blood flow reduction to 60% of control increased the amniotic fluid prostaglandin F metabolites concentration to 894 +/- 202 (p < 0.05, analysis of variance). No increase in mean intrauterine pressure was detected (p > 0.1).

CONCLUSIONS

We speculate that the prostaglandin increase in amniotic fluid in response to intrauterine hypoxia could eventually lead to premature labor. Whether the increase in prostaglandins is mediated by changes in cytokines is unknown at the present time.