SODIUM, POTASSIUM AND AGE: POSSIBLE DETERMINANTS OF PLASMA RENIN ACTIVITY AND ALDOSTERONE DURING CHILDHOOD (AGE 4–16)

The renin-angiotensin-aldosterone system was studied in fifty healthy children aged 4–16 years under normal sodium and potassium intake. The plasma renin activity (PRA) and plasma aldosterone (PA) decreased with age: r =−0·30, P < 0·05 for plasma renin activity and r =−0·33, P < 0·05 for plasma aldosterone. Significant negative correlation was obtained between plasma renin activity and the 24-h urinary sodium excretion; r =−0·40, P < 0·01. This relationship remained significant when the daily urinary sodium excretion was corrected for 1·73 m² body surface area (BSA); r =−0·40, P < 0·01. Using the multivariance analysis, plotting the plasma renin activity against the two combined parameters (24-h urinary sodium excretion and age), no improvement was obtained (r = 0·38, P > 0·05). This finding suggests that during childhood, sodium rather than age has a major modulatory role on plasma renin activity. With advancing age the plasma aldosterone showed a significant positive correlation coefficient with plasma renin activity (r = 0·29, P < 0·05). Multivariance analysis between plasma aldosterone and the two combined parameters, plasma renin activity and age, significantly improved the correlation coefficient (r = 0·42, P < 0·05) suggesting that both plasma renin activity and age play a dominant modulatory role in the control of plasma aldosterone during childhood. Neither 24-h urinary sodium excretion, nor 24-h urinary potassium excretion, improved the multiple correlation coefficient with plasma aldosterone when added to plasma renin activity and age.     

Cyclosporin Increases the CNS Sensitivity to the Hypnotic Effect of Phenobarbitone but not Ethanol in Rats

Abstract— The purpose of this investigation was to determine whether repetitive administration of cyclosporin affects the pharmacodynamics of phenobarbitone- and ethanol-induced anaesthesia. Sabra male rats received either cyclosporin (50 mg kg^?1 day^?1, i.m.) for four days, or the same volume of the vehicle. Two hours after the last cyclosporin dose, phenobarbitone or ethanol solutions were infused intravenously at a constant rate until the onset of anaesthesia. Repetitive treatment with cyclosporin increased the CNS sensitivity to the hypnotic action of phenobarbitone. This was evidenced by the lower CSF phenobarbitone concentration, at the onset of the hypnotic effect, in the cyclosporin-treated group vs control values (115 ± 4 vs 93 ± 7 mg L^?1, P = 0·01). However, the same pretreatment had no apparent effect on the pharmacodynamics of ethanol-induced sleep. It is suggested that anaesthesiologists must be alert to the possible increase in brain sensitivity when placing cyclosporin patients under anaesthesia with barbiturates.     

Antibodies to Beta-Adrenergic Receptors Disclosing Agonist-Like Properties in Idiopathic Dilated Cardiomyopathy and Chagas' Heart Disease

Antibodies to Beta-Adrenergic Receptors. Recent studies confirm the existence of antibodies (Abs) to β adrenoceptors in patients with idiopathic dilated cardiomyopathy and Chagas' heart disease. These Abs can be shown to exert both stimulatory and inhibitory effects, which may play a role in the development of the cardiac abnormalities known to occur in these diseases, including advanced heart failure. The hypothesis is advanced that Chagas' heart disease and some forms of idiopathic dilated cardiomyopathy may represent, at least partially, a form of "adrenergic cardiomyopathy."     

Effects of Ischemia on Repolarization in Patients with Single and Multivessel Coronary Disease

GIEDRIMIENE, D., et al. : Effects of Ischemia on Repolarization in Patients with Single and Multivessel Coronary Disease . To evaluate if QT dispersion (QTd) may be affected by the number of obstructed coronary arteries (CAs) in patients with acute myocardial infarction (MI) and undergoing angioplasty, and to evaluate if QTd may be affected by ejection function of the heart. The infarct related CA was identified by coronary angiography in 141 patients (97 men, mean age   61.6 ± 12.9   years) with acute MI undergoing percutaneous angioplasty. Successful reperfusion was defined as TIMI III flow with <20% residual stenosis. QTd, calculated by subtracting the shortest from the longest QT interval on 12-lead electrocardiograms, was examined immediately before and after angioplasty, at 24 hours, and 3 days after angioplasty. Successful reperfusion was achieved in 98 (69.5%) patients. Prolonged QTd at baseline was found in all patients with ischemia. A trend toward a decrease in QTd was observed immediately after angioplasty and at 24 hours, and a significant decrease at 3 days in patients with successful reperfusion regardless of the number of occluded CAs. There was no change in QTd found in patients with no reperfusion. An increase in QTd was observed in patients with acute ischemia due to single or multivessel disease. (PACE 2003; 26[Pt. II]:390–393)