摘要:

ObjectiveTo investigate a possible direct action of vasoactive intestinal polypeptide (VIP) on adrenal cortisol secretion and to define its mechanism of action.DesignThe human adrenocortical carcinoma cell line NCI H295, which is not contaminated by medullary chromaffin cells, was used to aid distinction between a direct action of VIP on adrenocortical cells and an indirect mechanism involving VIP-stimulated release of catecholamines.MethodsNCI H295 cells were challenged with 10−11-10−7mol/l VIP for 4 h, with or without prior exposure for 72 h to 10 mmol/l forskolin. Cortisol and cyclic AMP contents of the overlying media were measured using in-house radioimmunoassays. Cells were treated with 10−8-10−6mol/l adrenaline or 3.3 × 10−8mol/l VIP with and without 10−8-10−6mol/l propranolol to exclude the possibility that an indirect mechanism of action involving β-adrenoceptors was operating.ResultsVIP treatment produced an increase in cortisol secretion without pre-incubation, but this was markedly enhanced by prior exposure of cells to forskolin. VIP was potent, with a threshold of 10−11mol/l (n = 4), reaching a maximum 3.9 ± 0.9-fold increase in effect on cells pre-exposed to forskolin (n = 4) by 3.3 × 10−8mol/l. This increase matched the 4 h response to 10 μmol/l forskolin. Cortisol secretion was accompanied by a parallel, dose-dependent increase in accumulation of cAMP.ConclusionsVIP potently and directly stimulates secretion of cortisol from these adrenocortical cells of human origin via an adenylate cyclase-coupled VIP receptor. These findings raise the possibility of a significant and direct effect of VIP in the control of steroid secretion from the adrenal cortex in humans.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveThe aim of the study was to find out whether the presence of hypertension affects heart rate variability in patients rehabilitated after myocardial infarction.DesignEchocardiography, exercise testing and 24 h Holter monitoring were performed before and after 27 days of early postdischarge cardiac rehabilitation.PatientsThe study population consisted of 64 patients aged 34–65 years (mean ± SD 51.6 ± 6.6) discharged from hospital after a first myocardial infarction who were subdivided into two groups, group A comprising 34 patients with arterial hypertension which had lasted 4.8 ± 2.1 years and group B comprising 30 normotensives.Main outcomeWe expected exercise rehabilitation to affect heart rate variability, exercise tolerance and myocardial ischemia in patients after myocardial infarction with and without arterial hypertension.ResultsAt baseline no intergroup differences were seen in the duration of exercise, workload and heart rate variability parameters. All parameters increased significantly after cardiac rehabilitation (P< 0.01): SD of all normal RR intervals 123.4 ± 30.0 versus 123.8 ± 30.0 ms; SD of the averages of normal RR intervals in all 5-min segments of the entire recording 115.1 ± 30.5 versus 116.3 ± 28.3 ms; mean of the SD of all normal RR intervals for all 5-min segments of the entire recording 49.0 ± 12.5 versus 48.3 ± 11.8 ms; square root of the mean of the sum of the squares of differences between adjacent RR intervals 29.7 ± 9.1 versus 28.0 ± 8.5 ms; percentage of differences between adjacent RR intervals > 50 ms 7.9 ± 6.0 versus 7.1 ± 6.1% (group A versus group B, respectively, NS). The duration of exercise and the workload were significantly increased (the rise was higher in normotensives). No differences were seen in the frequency and severity of silent myocardial ischemia.ConclusionsEarly stationary exercise rehabilitation after myocardial infarction improves heart rate variability parameters and exercise tolerance both in hypertensives and in normotensives.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo examine the relationships among the circadian rhythms of blood pressure, autonomic nervous function, and physical activity of patients with varying levels of spinal cord injury.Design and methodsWe studied 19 patients with spinal cord injury [10 tetraplegic patients with cervical cord injury (C4–C7), and nine paraplegic patients with thoracic cord injury (Th6–Th12)] compared with 16 control subjects. A new multibiomedical recorder was used to measure blood pressure (every 30 min), cardiac vagal activity (hourly frequency of R-R50), and physical activity (integrated acceleration/min) for 24 h under hospital conditions. Systemic sympathetic nervous activity and sympathoadrenal functioning were assessed by examination of hormone levels in the blood.ResultsDaytime and night-time values were compared; the variations in systolic and diastolic blood pressures and heart rate were slight in members of the tetraplegia group, but almost normal differences were observed in members of the paraplegia group. The circadian profile of cardiac vagal activity was normal for both patient groups, suggesting that an alteration in the sympathetic nervous rhythm had occurred in the tetraplegic patients. The plasma norepinephrine level was lower in members of the tetraplegia group than it was in members of the control group (P< 0.001), but was normal in members of the paraplegia group. The plasma level of epinephrine was lower in members of the tetraplegia (P< 0.05) and the paraplegia (P< 0.1) groups than it was in members of the control group. Daytime physical activity of members of both groups of patients was lower than that of subjects in the control group (P< 0.001 for both).ConclusionThe central sympathoexcitatory pathway to the upper thoracic cord plays a critical role in the maintenance of normal circadian blood pressure rhythm in humans. Motor nerve functioning and sympathoadrenal secretion are not essential to this regulation.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveExcessive adrenergic responses have been reported in hypertensive patients treated with short-acting dihydropiridine calcium channel antagonists that might worsen cardiovascular risk. In this study we addressed whether lacidipine, a long-acting dihydropiridine, increases the sympathetic excitation produced by moderate dynamic exercise.DesignBecause of the wide changes in autonomic drive during everyday life, the possible influence of antihypertensive regimens should be assessed not only at rest but also during spontaneous, behaviourally induced alterations of sympathovagal balance. This study was designed to test whether treatment with lacidipine might alter the autonomic response to supine moderate dynamic exercise.MethodsWe studied 16 moderate hypertensive patients (arterial pressure 151/102 mmHg) at rest and during 30% of nominal maximum recumbent bicycle exercise. The low frequency spectral component of RR interval and of systolic variability (Finapres) furnished markers of sympathetic modulation of the sinoatrial node and of the vasculature, respectively. Studies were performed during placebo and active treatment (lacidipine 4 mg per day).ResultsLacidipine treatment significantly reduces arterial pressure values at rest and during moderate dynamic exercise, without affecting RR interval and systolic arterial pressure variabilities, both at rest and during moderate exercise.ConclusionsIn conclusion, spectral analysis of RR interval and systolic arterial pressure variabilities indicate that antihypertensive treatment with lacidipine is not associated to an excessive sympathetic drive during moderate exercise.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveThe generalized sympathetic activation induced by exercise is accompanied by an increase in heart rate, blood pressure and vascular resistance in non-exercising vascular beds. The aim of the present study was to test the feasibility of assessing, non-invasively, the static and oscillatory pressure/flow relationships of peripheral arteries and their continuous changes during dynamic exercise.DesignWe studied 44 healthy humans at rest, during moderate exercise (recumbent bicycle exercise) and recovery using a totally non-invasive approach.MethodsArterial pressure was measured using a plethysmographic device, and ipsilateral brachial artery flow and palmar skin microcirculation flow were assessed with continuous wave Doppler and laser Doppler, respectively. Continuous, long data segments (> 90 s) were acquired with a personal computer and used to determine the changes of pressure/flow relationships of peripheral arteries during dynamic exercise. A new simplified method utilizing a transfer function analysis extracted automatically unequivocal indexes of static and oscillatory properties of vascular system.ResultsModerate exercise induced significant increases of the static (Z0) and oscillatory (Zc) components of peripheral pressure/flow relationships in both brachial artery and skin microcirculation beds. Both indexes returned to control values during early recovery.ConclusionsThis simple, non-invasive approach was capable of assessing the changes of static and oscillatory vascular properties induced by dynamic exercise. This method could be applied for a better understanding of the vascular modifications that occur in other physiological or pathophysiological conditions also characterized by increases in sympathetic drive.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveAt present, non-invasive continuous monitoring of finger arterial blood pressure by the volume-clamp technique is considered the best approach to obtain reliable assessments of beat-to-beat blood pressure. However, data on the reproducibility (accuracy and precision) of prolonged recordings and of the hemodynamics derived from wave-form analysis are not available.DesignTen patients with untreated essential hypertension and eight normotensive subjects were monitored by Portapres over 24 h in the hospital on two occasions with 1–4 weeks in-between. Physical and mental activities were standardized as far as possible to minimize intra- and intersubject biological variability. Stroke volume was obtained by the Modelflow method. Differences between the two recordings were computed separately for the day (0700 to 2300 h) and the night (2300 to 0700 h) and for all hours. Differences in stroke volume were calculated as percentage change from the first recording.ResultsAccuracy was good in both groups and bias was close to zero. Precision was also remarkable in the daytime, and at least as good as values reported in studies that used the standard intra-arterial recording. The SD of the differences in systolic and diastolic pressure in the hypertensives in the daytime were 6.6 and 4.7 mmHg, respectively. At night, precision was less good, possibly because of the 30 min finger-cuff switching: 12.5 and 6.5 mmHg for systolic and diastolic pressure, respectively. The average stroke volume did not change more than 8% at most between the first and the second recordings.ConclusionThese results indicate that the Finapres and Portapres devices are a reliable substitute for intra-arterial recording, and are most useful instruments for the study of blood pressure regulation.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectivesTo clarify whether the functional changes during the transition from compensatory myocardial hypertrophy to failure are associated with changes in sarcoplasmic reticulum gene expression.MethodsWe examined the gene expression of sarcoplasmic reticulum proteins [sarcoplasmic reticulum Ca2+-ATPase (SERCA), phospholamban, calsequestrin and ryanodine receptor] in Dahl salt-sensitive (Dahl-S) rats fed a high-salt (8%) diet from the age of 6 weeks. In-vivo contractile functioning was evaluated using echocardiography, and gene expression of sarcoplasmic reticulum proteins in the left ventricle was analyzed by Northern blotting for each stage of left ventricular hypertrophy.ResultsSERCA messenger RNA (mRNA) levels in Dahl-S rats with compensatory hypertrophy did not change significantly, whereas phospholamban mRNA levels were increased by 61% (P< 0.01), and calsequestrin mRNA levels were increased by 130% (P< 0.01) compared with those in Dahl salt-resistant (Dahl-R) rats. SERCA mRNA levels in Dahl-S rats with decompensated dilatation were decreased by 32% (P< 0.05), whereas levels of phospholamban and calsequestrin mRNA remained unchanged. Ryanodine receptor mRNA levels did not change either with compensatory hypertrophy or with decompensated dilatation.ConclusionsAlterations in expression of sarcoplasmic reticulum gene may be related to changes in systolic and diastolic properties in compensatory hypertrophy and heart failure.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundCalpains are cytoplasmic proteases widely distributed among eucaryotic cells. Low levels of calpain activity were found in hypertrophic hearts from hypertensive rats, but its role in hypertrophic hearts from human hypertensives is unknown. Therefore, calpain activity was investigated in erythrocytes from essential hypertensive patients in relation to their left ventricular mass.ObjectiveTo study the role of calpain activity in the development of left ventricular hypertrophy (LVH) in human essential hypertension.MethodsA total of 115 hypertensives (72 untreated and 43 with treatment interrupted for at least 4 months) were included in the study. Calpain I activity was measured in human erythrocytes and LVH was measured as left ventricular mass index (LVMI) by M-mode echocardiography.ResultsValues are given as mean ± SEM. The hypertensives (97 men and 18 women) were 43.5 ± 0.9 years old with mild to moderate levels of hypertension (systolic/diastolic blood pressure of 147.9 ± 1.4/98.7 ± 0.9 mmHg) and relatively recent LVH onset (3.5 ± 0.5 years). An inverse relation between LVMI and erythrocytic calpain activity was present in all (P= 0.0023, R2= 7.9%). This relation was still present considering only untreated hypertensives (P= 0.008; R2= 9.7%), but was lost in the 43 previously treated hypertensives. Moreover, in the untreated hypertensives, after excluding the possible confounding effects of sex, age, body mass index, blood pressure and duration of hypertension, a stepwise regression showed that only two variables remained significantly related to LVMI: calpain (F = 6.23) and mean arterial pressure (F = 4.689). No relations were found between LVMI and calpastatin activity either in the whole population, or in treated or untreated hypertensives.ConclusionsIf we assume that the level of erythrocyte calpain activity mirrors the level in cardiomyocytes, these data seem to suggest that increased protein degradation by calpain may prevent the development of LVH in hypertensive patients. This effect is independent of the duration and severity of hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveHypertensive left ventricular hypertrophy is associated with an increased risk of arrhythmias and mortality. However, no clinical study has demonstrated a significant relationship between ventricular arrhythmias and mortality in systemic hypertension.Design and methodsTo evaluate the prognostic value of arrhythmogenic markers, we included, prospectively, 214 hypertensive patients aged (mean ± SD) 59.1 ± 12.8 years, without symptomatic coronary disease, myocardial infarction, systolic dysfunction or electrolyte disturbances. At inclusion, a 12-lead electrocardiogram (ECG) with QT dispersion calculation, a 24 h Holter ECG (204 patients) with Lown classification of ventricular arrhythmias, echocardiography (reliable in 187 patients) and a signal-averaged ECG (125 patients) with ventricular late potentials were recorded.ResultsAt baseline, echocardiographic left ventricular hypertrophy was found in 63 patients (33.7%). Non-sustained ventricular tachycardia (Lown class IVb) was recorded in 33 patients (16.2%) and late potentials in 27 patients (21.6%). After a mean follow-up of 42.4 ± 26.8 months, all-cause mortality was 11.2% (24 patients); 17 patients died of cardiac causes (7.9%); of these, nine (4.2%) died suddenly. In univariate analysis, age, Lown class IVb and a QT dispersion > 80 ms were significantly related to global, cardiac and sudden death (P< 0.01). The left ventricular mass index was related to cardiac mortality (P= 0.002). In multivariate analysis, only Lown class IVb was an independent predictor of global and cardiac mortality, increasing the risk of global death 2.6-fold (95% confidence interval 1.2–6.0) and cardiac death 3.5-fold (95% confidence interval 1.2–9.7).ConclusionIn hypertensive patients the presence of non-sustained ventricular tachycardia has prognostic value.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectivesTo investigate the effects of the interaction between adenosine receptors and renal nerves on urinary sodium excretion and glomerular filtration rate.Methods and designThe effects on water and sodium excretion and glomerular filtration rate of A1 [2-chloro-N6-cyclopentyl-adenosine (CCPA)] and A2 [2-hesinyl-5′-N-ethyl-carboxamido-adenosine (2HE-NECA)] adenosine agonists were studied in anaesthetized rats with one kidney surgically denervated. Arterial blood pressure, heart rate and rate of urine flow from each kidney were continuously recorded; inulin clearance was used as an index of glomerular filtration rate. The experiments were performed with three groups of rats, into which, after a control period of 20 min, CCPA, 2HE-NECA or vehicle was infused for two subsequent 20 min periods.ResultDuring infusion of CCPA, the slight decrease in arterial pressure was associated with a transient decrease in glomerular filtration rate and marked long-lasting decreases in heart rate, water and sodium excretion and fractional sodium excretion. The response of the innervated kidney was similar to the response of the denervated kidney. Infusion of 2HE-NECA caused decreases in arterial pressure, glomerular filtration rate and excretion of water and sodium associated with an increase in heart rate. The reduction of water and sodium excretion from the innervated kidney was larger than that from the denervated kidney.ConclusionsActivation both of A1 and of A2 receptor causes a reduction in urinary water and sodium excretion. The renal response to activation of A2 receptors is enhanced by the presence of renal nerves, whereas the response to activation of A1 receptors is not influenced by renal nerves.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID