Dyslipidemia without obesity in indigenous Argentinean children living at high altitude

OBJECTIVES

To compare the prevalence of cardiovascular disease risk factors in Indian children from San Antonio de los Cobres (SAC) and children from Buenos Aires (BA), and to examine body mass index (BMI), waist circumference (WC), and WC/height as predictors of dyslipidemia in both groups.

STUDY DESIGN

Data were collected cross-sectionally from BMI, WC, blood pressure, Tanner scale, glucose, lipids, and insulin. Dyslipidemia was defined by the National Cholesterol Education Program and American Heart Association.

RESULTS

The mean ages were 10.6 ± 3.0 and 9.5 ± 2.0 years in SAC vs BA children. Of the 330 SAC children, 15 (4.5%) were overweight and 12 (3.6%) obese, and of the 603 BA, 97 (16.1%) were overweight and 82 (13.6%) obese per Centers for Disease Control. There was a significantly higher prevalence of high triglycerides (28.8% vs 3.5%) and low high-density lipoprotein cholesterol (30.0% vs 5.5%) in SAC vs BA children. The areas under the receiver operating characteristic curve in predicting high triglycerides were BMI = 0.55 (95% CI, 0.48-0.62; P = .15) in SAC and BMI = 0.65 (95% CI, 0.52-0.77; P = .02) in BA children. Similar results from the areas under the receiver operating characteristic curve were obtained when low high-density lipoprotein cholesterol was used, indicating that BMI was not a significant predictor for dyslipidemia in SAC children. When BMI was replaced by WC and WC/height, results were similar.

CONCLUSIONS

Anthropometric markers were not an acceptable predictor for National Cholesterol Education Program cutoffs for dyslipidemia in SAC children. Longitudinal studies should determine if SAC children are at high risk for cardiovascular diseases because of genetic background.

Impact of magnetic resonance cholangiography in managing liver-transplanted patients: preliminary results of a clinical decision-making study

PURPOSE

This study was performed to assess the role of magnetic resonance cholangiography (MRC) in the clinical decision-making process of referring physicians when managing liver-transplanted patients.

MATERIALS AND METHODS

Over a 6-month period, 21 liver-transplanted patients with a suspected biliary complication were referred for MRC. Referring physicians were asked to prospectively state, before and after MRC, the leading diagnosis; the level of confidence (on a 0-100% scale); the most appropriate diagnostic/therapeutic plan. Data analysis assessed was the diagnostic yield of MRC; the proportion of change in the leading diagnosis; the therapeutic efficacy (i.e. proportion of change in the initial diagnostic/therapeutic plan); the diagnostic thinking efficacy (i.e., gain in diagnostic confidence). Statistical significance was assessed with the Mann-Whitney U test. MRC accuracy was also calculated.

RESULTS

Data analysis showed a diagnostic yield of 85.7%; a proportion of change in leading diagnosis of 19.0%; a therapeutic efficacy of 42.8%; a diagnostic thinking efficacy for concordant and discordant leading diagnoses of 18.8% and 78.7%, respectively (p<0.01). MRC accuracy was 92.3%.

CONCLUSIONS

MRC significantly increased the diagnostic confidence, irrespective of the concordance between pre- and posttest diagnoses. Moreover, MRC determined a change in patient management in a significant proportion of cases, leading to clinical benefits.

Comparison of different anthropometric indices for identifying dyslipidemia in school children

BACKGROUND

Anthropometric indices have been associated with dyslipidemia.

OBJECTIVE

To compare the abilities of BMI, waist circumference (WC) and WC/height to identify children's dyslipidemia.

METHODS

Students 1261 (639 male) age 9.5±2.1 years. were examined for anthropometry and lipid levels. Triglycerides ≥1.69 mmol/L and high-density lipoprotein cholesterol (HDL-C) <0.91 mmol/L were considered abnormal per American Heart Association.

RESULTS

The prevalence of abnormal triglycerides was 4.1% and HDL-C 8.1%. The areas under the receiver operator curves (ROC) were: BMI=0.87, WC=0.83, and WC/height=0.84 in predicting both low HDL-C and high triglycerides. Multiple regression analyses showed that the odds ratios (OR) were highest for WC [6.5], followed by WC/height [5.4], and BMI [4.9], for dyslipidemia.

CONCLUSIONS

The results suggest that WC, WC/height, and BMI similarly predicted dyslipidemia, using ROC analyses. However, regression analyses showed that WC followed by WC/height was most predictive of dyslipidemia.

Is albuminuria associated with obesity in school children?

BACKGROUND

Different studies in adults have shown that obesity is an independent risk factor for end-stage renal disease.

OBJECTIVE

It was to (i) determine the association between albuminuria and age, gender, BMI, waist circumference (WC), and blood pressure (ii) relate albuminuria to gender and age in healthy school children.

METHODS

Over 1564 students (806 males) aged 9.35 +/- 2.00 yr from 9 elementary schools in Buenos Aires, were examined between April and September 2005. BMI, WC, blood pressure, urinary albumin excretion and albumin/creatinine ratio (ACR) were determined.

RESULTS

Over 220 (14.1%) children were obese (OB), and 300 (19.2%) overweight (OW) using centers for disease control (CDC) norms. Median ACR and urinary albumin levels were higher in normal weight children than in OW/OB children (p < 0.01). Median values for ACR were higher in girls than in boys (p < 0.001). OW/OB proved to be a protective factor against ACR [OR, 0.77 (95% CI 0.64-0.92)], whereas female gender [OR, 2.72 (95% CI 2.13-3.47)] was associated with a higher ACR adjusted for age systolic and diastolic blood pressure in the multiple logistic regression analysis. Therefore, children with OW/OB had 23% lower odds of having ACR >or= III quartile and girls had more than two and half times the risk of having high ACR.

CONCLUSIONS

Our results suggest that OW/OB is inversely associated with childhood albuminuria while female gender is positively associated. Whether the results can be explained by the increased physical activity in lean children should be the subject of future investigations. These results suggest that micro-albuminuria in children may not be a useful tool in the early identification of children at risk for future renal and cardiovascular disease (CVD).

Comparison of various maternal anthropometric indices of obesity for identifying metabolic syndrome in offspring

BACKGROUND

Several maternal anthropometric markers have been associated with the metabolic syndrome (MS) in offspring. The objectives of this study were (1) to determine the association between children's MS and maternal anthropometric markers such as body mass index (BMI), waist circumference (WC), WC/height, weight/sitting height squared, and WC/sitting height and (2) to compare the abilities of these five indices to identify children with MS.

METHODS

Data were collected cross-sectionally from five elementary schools between April 2007 and March 2008. BMI, WC, WC/height, weight/sitting height squared, and WC/sitting height were acquired in mothers and their children. Tanner stage, blood pressure, glucose, lipids, and insulin were measured in children. Criteria analogous to Adult Treatment Panel III for MS were used for children.

RESULTS

Of 624 children (307 boys) 8.96 +/- 1.86 years old, with their mothers being 36.25 +/- 7.14 years old, examined, 107 (17.1%) of children were obese (BMI >95th percentile per Centers for Disease Control and Prevention norms), and 95 (15.2%) were overweight (OW) (85th percentile < or =BMI < 95th percentile). Of the mothers, 109 (30.4%) were obese (BMI > 30 kg/m(2)), and 206 (33.0%) were OW (25 kg/m(2) < BMI < 30 kg/m(2)). Approximately 68% of the children were prepubertal. The prevalence of MS was 3.5% overall: 6.7% in OW and 13.9% in obese children. To determine which marker was a better predictor for MS, a receiver operating characteristics (ROC) curve was generated for the five maternal anthropometric measures, with children's MS as the dichotomous variable. The areas under the ROC curves were 0.697 +/- 0.07 for BMI, 0.698 +/- 0.07 for WC, 0.717 +/- 0.07 for WC/height, 0.725 +/- 0.07 for WC/sitting height, and 0.704 +/- 0.07 for weight/sitting height squared. There was no significant difference between the areas of the five maternal anthropometric markers as predictors of children's MS.

CONCLUSIONS

Measurement of maternal sitting height had no advantages over total height in the prediction of children's MS. All maternal anthropometric measures identified the MS in their children consistent with known familial associations of obesity and type 2 diabetes.

Mortality and causes of death in Italian persons with haemophilia, 1990-2007

Although a number of studies have analysed so far the causes of death and the life expectancy in haemophilic populations, no investigations have been conducted among Italian haemophilia centres. Thus, the aim of this study was to investigate mortality, causes of deaths, life expectancy and co-morbidities in Italian persons with haemophilia (PWH). Data pertaining to a total of 443 PWH who died between 1980 and 2007 were retrospectively collected in the 30 centres who are members of the Italian Association of Haemophilia Centres that chose to participate. The mortality rate ratio standardized to the male Italian population (SMR) was reduced during the periods 1990-1999 and 2000-2007 such that during the latter, death rate overlapped that of the general population (SMR 1990-1999: 1.98 95% CI 1.54-2.51; SMR 2000-2007: 1.08 95% CI 0.83-1.40). Similarly, life expectancy in the whole haemophilic population increased in the same period (71.2 years in 2000-2007 vs. 64.0 in 1990-1999), approaching that of the general male population. While human immunodeficiency virus infection was the main cause of death (45%), 13% of deaths were caused by hepatitis C-associated complications. The results of this retrospective study show that in Italian PWH improvements in the quality of treatment and global medical care provided by specialized haemophilia centres resulted in a significantly increased life expectancy.

Comparison of different anthropometric indices for identifying insulin resistance in schoolchildren

OBJECTIVES

Anthropometric indices have been associated with insulin resistance in children. This study (1) determined the association between insulin resistance and anthropometric indices, including body mass index (BMI), waist circumference (WC), WC/height, weight/(sitting height)(2), and WC/sitting height, and (2) compared the abilities of these five indices to identify children with insulin resistance.

METHODS

Data were collected from six elementary schools in Argentina between April and August 2007. Anthropometric data and Tanner staging were obtained. Fasting serum concentrations of glucose, lipids, and insulin were measured.

RESULTS

Six hundred twenty-five children (318 boys) between 6 and 14 years old were examined. The mean age of the children was 9.6 +/- 2.0 years. Ninety-six (15.4%) of the children were obese, 91 (14.6%) were overweight, and 438 (70.1%) were normal weight using Centers for Disease Control and Prevention norms. Sixty percent, 23.0%, 14.0%, and 3.0% were Tanner stage I, II, III, and IV, respectively. The areas under the receiver operator characteristic curves were as follows: WC = 0.78 +/- 0.021 (95% confidence interval [CI] 0.74-0.82), BMI = 0.77 +/- 0.022 (95% CI 0.73-0.82), weight/(sitting height)(2) = 0.76 +/- 0.022 (95% CI 0.72-0.81), WC/height = 0.67 +/- 0.027 (95% CI 0.62-0.72), and WC/sitting height = 0.67 +/- 0.27 (95% CI 0.62-0.72), indicating that BMI, WC, and weight/(sitting height)(2) were acceptable predictors for insulin resistance, whereas WC/height and WC/sitting height were fair predictors as the areas under the curve were <0.7.

CONCLUSIONS

This study suggests that WC and BMI are (and remain) the best correlates for insulin resistance. In contrast, the indices of the ratio between WC and height were fair predictors for insulin resistance. Additional longitudinal studies should be done to further confirm these findings.

Levosimendan induces NO production through p38 MAPK, ERK and Akt in porcine coronary endothelial cells: role for mitochondrial K(ATP) channel

BACKGROUND AND PURPOSE

Levosimendan acts as a vasodilator through the opening of ATP-sensitive K(+) channels (K(ATP)) channels. Moreover, the coronary vasodilatation caused by levosimendan in anaesthetized pigs has recently been found to be abolished by the nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine methyl ester, indicating that nitric oxide (NO) has a role in the vascular effects of levosimendan. However, the intracellular pathway leading to NO production caused by levosimendan has not yet been investigated. Thus, the purpose of the present study was to examine the effects of levosimendan on NO production and to evaluate the intracellular signalling pathway involved.

EXPERIMENTAL APPROACH

In porcine coronary endothelial cells (CEC), the release of NO in response to levosimendan was examined in the presence and absence of N(omega)-nitro-L-arginine methyl ester, an adenylyl cyclase inhibitor, K(ATP) channel agonists and antagonists, and inhibitors of intracellular protein kinases. In addition, the role of Akt, ERK, p38 and eNOS was investigated through Western blot analysis.

KEY RESULTS

Levosimendan caused a concentration-dependent and K(+)-related increase of NO production. This effect was amplified by the mitochondrial K(ATP) channel agonist, but not by the selective plasma membrane K(ATP) channel agonist. The response of CEC to levosimendan was prevented by the K(ATP) channel blockers, the adenylyl cyclase inhibitor and the Akt, ERK, p38 inhibitors. Western blot analysis showed that phosphorylation of the above kinases lead to eNOS activation.

CONCLUSIONS AND IMPLICATIONS

In CEC levosimendan induced eNOS-dependent NO production through Akt, ERK and p38. This intracellular pathway is associated with the opening of mitochondrial K(ATP) channels and involves cAMP.

GABAA receptors expression pattern in rat brain following low pressure distension of the stomach

It is known that gastric mechanoreceptor stimuli are widely integrated into neuronal circuits that involve visceral nuclei of hindbrain as well as several central brain areas. GABAergic neurons are widely represented in hindbrain nuclei controlling gastric motor functions, but limited information is available specifically about GABA(A)-responding neurons in brain visceral areas. The present investigation was designed to determine the central sensory neuronal pathways and their GABA(A)-alpha1 and -alpha3 receptor presenting neurons that respond to gastric mechanoreceptor stimulation within the entire rat brain. Low pressure gastric distension was used to deliver physiological mechanical stimuli in anesthetized rats, and different protocols of gastric distension were performed to mimic different stimulation patterns with and without sectioning vagal and/or splanchnic afferent nerves. Mapping of activated neurons was investigated using double colorimetric immunohistochemistry for GABA(A)-alpha1 or -alpha3 subunits and c-Fos. Following stomach distension, neurons expressing GABA(A) receptors with alpha1 or alpha3 subunits were detected. Low frequency gastric distension induced c-Fos expression in nucleus tractus solitarii (NTS) only, whereas in the high frequency gastric distension c-Fos positive nuclei were found in lateral reticular nucleus and in NTS in addition to some forebrain areas. In contrast, during the tonic-rapid gastric distension the neuronal activation was found in hindbrain, midbrain and forebrain areas. Moreover different protocols of gastric stimulation activated diverse patterns of neurons presenting GABA(A)-alpha1 or -alpha3 receptors within responding brain nuclei, which may indicate a probable functional significance of differential expression of GABA(A)-responding neurons. The same protocol of gastric distension performed in vagotomized rats has confirmed the primary role of the vagus in the response of activation of gastric brain areas, whereas neuronal input of splanchnic origins was shown to play an important role in modulating the mechanogastric response of brain areas.

Modulation of apoptotic signalling by 9-hydroxystearic acid in osteosarcoma cells

9-hydroxystearic acid (9-HSA) belongs to the class of endogenous lipid peroxidation by-products that greatly diminish in tumors, causing as a consequence the loss of one of the control mechanisms on cell division. We have previously shown that 9-HSA controls cell growth and differentiation by inhibiting histone deacetylase 1 (HDAC1) activity. In this paper our attention has not only been focused on HDAC1 inhibition but also on the hyperacetylation of other substrates such as p53, that is involved in inducing cell cycle arrest and/or apoptosis, and whose activity and stability are known to be regulated by posttranslational modifications, particularly by acetylation at the C-terminus region. 9-HSA administration to U2OS, an osteosarcoma cell line p53 wt, induces a growth arrest of the cells in G2/M and apoptosis via a mitochondrial pathway. In particular hyperacetylation of p53 induced by the HDAC1 inhibitory activity of 9-HSA has been demonstrated to increase Bax synthesis both at the transcriptional and the translational level. The subsequent translocation of Bax to the mitochondria is associated to a significant increase in caspase 9 activity. Our data demonstrate that the effects of 9-HSA on U2OS correlate with posttranslational modifications of p53.

The role of nitric oxide in the peripheral vasoconstriction caused by human placental lactogen in anaesthetized pigs

Regional intra-arterial infusion of human placental lactogen in anaesthetized pigs has been shown to cause coronary, renal and iliac vasoconstriction by antagonizing the vasodilatory effects of beta2-adrenergic receptors. Since nitric oxide is known to modulate or mediate beta2-adrenergic effects, the present study was planned in the same experimental model to determine the role of nitric oxide in the above vascular responses to human placental lactogen. In eight pigs anaesthetized with sodium pentobarbitone, changes in anterior descending coronary, left renal and left internal iliac blood flow caused by intra-arterial infusion of human placental lactogen at constant heart rate and arterial blood pressure were assessed using electromagnetic flowmeters. Intra-arterial infusion of the human placental lactogen caused decreases in coronary, renal and iliac blood flow which, respectively, averaged 16.7, 8.1 and 12.2% of the baseline values. The role of nitric oxide in this response was studied in the same pigs by repeating the experiments, after measured blood flows had returned to baseline values, following intra-arterial administration of N(omega)-nitro-L-arginine methyl ester (L-NAME). The subsequent intra-arterial infusion of human placental lactogen did not cause any significant changes in measured blood flows, even when performed after reversing the increase in arterial blood pressure and coronary, renal and iliac resistance caused by L-NAME with continuous intravenous infusion of papaverine. These results indicate that the coronary, renal and iliac vasoconstriction caused by human placental lactogen, known to involve antagonism of beta2-adrenergic vasodilatory effects, was mediated by inhibition of nitric oxide release.

Human Placental Lactogen Decreases Regional Blood Flow in Anesthetized Pigs

In 22 pigs anesthetized with sodium pentobarbitone, changes in blood flow caused by infusion of human placental lactogen into the left renal, external iliac, and anterior descending coronary arteries were assessed using electromagnetic flowmeters. In 17 pigs, infusion of human placental lactogen whilst keeping the heart rate and arterial pressure constant decreased coronary, renal and iliac flow. In 5 additional pigs, increasing the dose of human placental lactogen produced a dose-related decrease in regional blood flow. The mechanisms of the above response were studied in 15 of the 17 pigs by repeating the experiment of infusion. The human placental lactogen-induced decrease in regional blood flow was not affected by blockade of cholinergic receptors (5 pigs) or of alpha-adrenergic receptors (5 pigs), but it was abolished by blockade of beta2-adrenergic receptors (5 pigs). The present study showed that intra-arterial infusion of human placental lactogen primarily decreased coronary, renal and iliac blood flow. The mechanism of this response was shown to be due to the inhibition of a vasodilatory beta2-adrenergic receptor-mediated effect.

Hemodynamic Effect of Intracoronary Administration of Levosimendan in the Anesthetized Pig

In this study the hemodynamic effects of intracoronary injection of levosimendan in anesthetized pigs and the mechanisms involved were examined. In 12 anesthetized pigs instrumented for measurement of heart rate (HR), aortic blood pressure (ABP), central venous pressure (CVP), left ventricular end-diastolic blood pressure, left ventricular contractility and relaxation, and mean coronary blood flow (CBF), levosimendan has been injected into the left anterior descending coronary artery at doses corresponding to the ones commonly used in clinics as bolus administration but adapted to the measured CBF. In a further 9 pigs levosimendan has been administered after the blockade of alpha and beta adrenoceptors, muscarinic receptors, and coronary nitric oxide synthase (NOS) to investigate the action mechanism of the drug. The intracoronary bolus administration of doses of levosimendan corresponding to 12 and 24 microg/kg in 10 minutes exerted, respectively, CBF increases of 26.3% and 41.3% of the control values in the absence of changes in the other hemodynamic variables. The blockade of the autonomic nervous system did not prevent the coronary vasodilation, which was, however, abolished by the NOS inhibition. The intracoronary administration of levosimendan exerts positive effects on myocardial blood supply without changes in ABP, HR, CVP, or in myocardial kinetics. The coronary effects of levosimendan are related to NO production.

The pattern of c-Fos immunoreactivity in the hindbrain of the rat following stomach distension

It has been previously shown that the walls of the stomach contain vagal and splanchnic afferents, connected to low and high threshold (LT and HT) gastric receptors, that convey physiological and noxious information to areas of the hindbrain involved mainly in the control of gastrointestinal function. Because distension of the stomach also reflexly increases the sympathetic drive to the cardiovascular system, the present study was planned to examine the pattern of activation of all nuclei encountered throughout the hindbrain in response to gastric distension. In anaesthetized rats, the stimulus was controlled by employing different transmural pressures and frequencies of distension, and c-Fos immunohistochemistry was used to characterize neuronal activation. Low intensity stimulation induced c-Fos expression in the cranial part of nucleus of solitary tract (NTS), the nucleus ambiguus (NA), the lateral reticular area (LRt) and the ventrolateral medulla (RVL/CVL). At low frequency of stimulation c-Fos positive nuclei (p.n.) were found in NTS only. At high frequency of stimulation an increase in c-Fos immunoreactivity was found. High intensity stimulation induced c-Fos expression in area postrema (AP), the lateral vestibular nucleus (LVe) and the caudal part of the NTS. At low frequency, only the number of c-Fos p.n. was increased. Increasing the frequency of stimulation induced c-Fos expression in further nuclei such as the parabrachial nucleus (PBN), the inferior olive subnuclei (IOn), the oral part of spinal trigeminal nucleus (Sp5O) and locus coeruleus (LC). At higher frequencies c-Fos immunoreactivity decreased in NTS and LRt, disappeared in VLM and increased in NA. Thus stomach distension activated several neuronal excitatory and inhibitory circuits that are involved in the control of gastrointestinal function as well as in cardiovascular, respiratory and pain regulation. The differences in c-Fos immunoreactivity induced by changing the distension patterns suggested interactions between groups of vagal and splanchnic afferents.

The effects of insulin on mesenteric blood flow in anaesthetized pigs

Infusion of insulin in anaesthetized pigs has been shown to cause an increase in renal blood flow and a decrease in coronary blood flow, which were the net result of a vasoconstriction involving sympathetic alpha-adrenoceptor-mediated mechanisms and of a local vasodilatation involving the endothelial release of nitric oxide. In the present study, the effect of insulin on superior mesenteric blood flow was examined in pentobarbitone-anaesthetized pigs at constant heart rate, aortic blood pressure, left ventricular contractility and blood levels of glucose and potassium. In 10 pigs, infusion of 0.004 IU kg(-1) min(-1) of insulin increased mesenteric flow. In five of these pigs, intravenous phentolamine enhanced the increase in mesenteric flow elicited by insulin, a response which was abolished by the subsequent injection of N(omega)-nitro-L-arginine methyl ester (L-NAME) into the mesenteric artery. In the remaining five pigs, infusion of insulin after intramesenteric injection of L-NAME caused a decrease in mesenteric flow. This response was abolished by the subsequent intravenous administration of phentolamine. The present study showed that infusion of insulin in anaesthetized pigs primarily caused a mesenteric vasodilatation, which was the net result of two opposite effects, namely a predominant vasodilatation mediated by the endothelial release of nitric oxide and a sympathetic vasoconstrictor mechanism mediated by alpha-adrenoceptors.

The effect of dehydroepiandrosterone on regional blood flow in prepubertal anaesthetized pigs

Dehydroepiandrosterone has been implicated in vascular disease and its associated insulin resistance and hypertension, though little is known about its vascular effects. We have recently shown in prepubertal anaesthetized pigs that intravenous infusion of dehydroepiandrosterone caused coronary vasoconstriction through the inhibition of a vasodilatory beta-adrenergic receptor-mediated effect related to the release of nitric oxide. The present study was designed to investigate the effect of dehydroepiandrosterone on mesenteric, renal and iliac vascular beds. In prepubertal pigs of both sexes anaesthetized with sodium pentobarbitone, changes in superior mesenteric, left renal and left external iliac blood flow caused by intravenous infusion of dehydroepiandrosterone were assessed using electromagnetic flowmeters. Changes in heart rate and arterial blood pressure were prevented by atrial pacing and by connecting the arterial system to a pressurized reservoir containing Ringer solution. In 22 pigs, infusion of 1 mg h(-1) of dehydroepiandrosterone decreased mesenteric, renal and iliac blood flow. In a further 10 pigs, dose-response curves were obtained by graded increases in the infused dose of hormone between 0.03 and 4 mg h(-1). The mechanisms of the above response were studied in the 22 pigs by repeating the experiment after haemodynamic variables had returned to the control values observed before infusion. Blockade of alpha-adrenoceptors with intravenous phentolamine (five pigs) did not affect the dehydroepiandrosterone-induced mesenteric, renal and iliac vasoconstriction. This response was abolished by blockade of beta(2)-adrenoceptors with intravenous butoxamine (five pigs) and by blockade of mesenteric, renal and iliac nitric oxide synthase with intra-arterial administration of N(omega)-nitro-L-arginine methyl ester (seven pigs), even after reversing the increase in local vascular resistance caused by the two blocking agents with intravenous infusion of papaverine. In five pigs, the increase in measured blood flow caused by intravenous infusion of isoproterenol (isoprenaline) was significantly reduced by infusion of dehydroepiandrosterone. The present study showed that intravenous infusion of dehydroepiandrosterone primarily caused mesenteric, renal and iliac vasoconstriction. The mechanisms of this response were shown to be due to the inhibition of a vasodilatory beta(2)-adrenergic receptor-mediated effect, which possibly involved the release of nitric oxide.

The effect of dehydroepiandrosterone on coronary blood flow in prepubertal anaesthetized pigs

Extensive research suspecting an association between plasma levels of dehydroepiandrosterone and the risk of coronary heart disease has not been conclusive. The present study was designed to investigate the effect of dehydroepiandrosterone on the coronary circulation and to determine the mechanisms involved. In prepubertal pigs of both sexes anaesthetized with sodium pentobarbitone, changes in left circumflex or anterior descending coronary flow caused by intravenous infusion of dehydroepiandrosterone were assessed using an electromagnetic flowmeter. Changes in heart rate and arterial pressure were prevented by atrial pacing and by connecting the arterial system to a pressurized reservoir containing Ringer solution. In 20 pigs, infusion of 1 mg h-1 of dehydroepiandrosterone caused a decrease in coronary flow without affecting left ventricular dP/dtmax (rate of change of left ventricular systolic pressure) and filling pressures of the heart. In a further eight pigs, a dose-response curve was obtained by graded increases in the infused dose of hormone between 0.03 and 4 mg h-1. The mechanisms of the above response were studied in the 20 pigs by repeating the experiment after haemodynamic variables had returned to the control values observed before infusion. Blockade of muscarinic cholinoceptors with intravenous atropine (five pigs) and of alpha-adrenoceptors with intravenous phentolamine (five pigs) did not affect the dehydroepiandrosterone-induced coronary vasoconstriction. This response was abolished by blockade of beta-adrenoceptors with intravenous propranolol (five pigs) and of coronary nitric oxide synthase with intracoronary injection of Nomega-nitro-L-arginine methyl ester (five pigs) even after reversing the increase in arterial pressure and coronary vascular resistance caused by the two blocking agents with intravenous infusion of papaverine. The present study showed that intravenous infusion of dehydroepiandrosterone primarily caused coronary vasoconstriction. The mechanisms of this response were shown to involve the inhibition of a vasodilatory beta-adrenergic receptor-mediated effect related to the release of nitric oxide.