Effect of antiarrhythmic therapy with intravenous loading dose of amiodarone: evidence for an altered response in diabetic patients

Amiodarone, a potent class III antiarrhythmic agent with adrenergic antagonism properties, is administered increasingly to diabetic patients with cardiac arrhythmias refractory to all other available forms of therapy. Because a large percentage of diabetic patients show a perturbed autonomic regulation of the cardiovascular system, including a pertubed regulation of heart rate, we studied the antiarrhythmic response as well as the early effects (within 5 days) on heart rate of an intravenous amiodarone loading dose in diabetic patients. Seven type II (noninsulin-dependent) diabetic patients (age 64.7 +/- 9.7 years), affected by uncontrolled atrial fibrilation or atrial flutter, were enrolled for the study and a group of 12 well-matched (for age, sex and arrhythmia) nondiabetic patients served as a control group. It was found that before amiodarone administration, nondiabetic patients showed significantly wider variations in the circadian rhythm of heart rate values than diabetic patients (p = 0.0062, unpaired t-test). In all patients but one (who was nondiabetic), amiodarone treatment resulted in a cardioversion to sinus rhythm. After amiodarone administration, nondiabetic patients showed a significantly greater decrease (p = 0.0011) in heart rate values in comparison with the diabetic group (-35% vs. -20% on average, at the end of the study). Furthermore, in nondiabetic patients there was also an earlier significant fall (within the first 4 h after the start of treatment with amiodarone, p < 0.001) in the heart rate values in comparison with diabetic patients, in whom a significant decrease (p < 0.001) was found only at the 4th day. A significant (p = 0.0004), more rapid onset of the antiarrhythmic response to the drug was found in nondiabetic patients (6.8 +/- 6.0 h) in comparison with diabetic patients (98.0 +/- 14.8 h). Our findings suggest that the antiarrhythmic effects of amiodarone in diabetic patients with uncontrolled atrial fibrilation or atrial flutter may be delayed in comparison with nondiabetic patients. This altered response may be (at least in part) due to the diabetic autonomic neuropathy. Our study indicates that the presence of diabetes mellitus always must be taken into account when patients are enrolled for large, prospective, randomized trials, planned to evaluate the antiarrhythmic effects of amiodarone given intravenously.

Atrial natriuretic peptide is not degraded by the lungs in humans

In an attempt to identify and quantify the sites of atrial natriuretic peptide (ANP) degradation, particularly the lungs, a new tracer method to study ANP metabolism in vivo in humans was developed and applied to patients with left ventricular dysfunction. Thirteen male, normotensive, cardiac patients with different degrees of left ventricular myocardial involvement were enrolled in the study. The study protocol required constant infusion (3 patients) or bolus injection (10 patients) of 125I-labeled ANP just upstream of the right atrium and blood sampling from different sites (pulmonary artery, aorta, inferior vena cava, and femoral vein) during the hemodynamic study. Data analysis was based on a kinetic model consisting of three blocks in series (right heart, lungs and left heart, and periphery) supplied by the same plasma flow (plasma cardiac output). Plasma levels of native ANP were measured with a sensitive and specific immunoradiometric assay method. ANP values measured in the aorta (163.9 +/- 144.8 pg/mL, n = 80) were superimposable on those measured in the pulmonary artery (161.8 +/- 136.5 pg/mL, n = 80). Negligible extraction of 125I-labeled ANP was found in the lungs and left heart block (on average 0.08 +/- 3.92%), whereas the peripheral block extraction (46.2 +/- 7.8%) accounted for almost total hormone removal from the blood (whole body extraction was 46.4 +/- 6.6%). ANP metabolic clearance rate (3.11 +/- 1.48, range 1.4-6.8 L/min) declined with the progression of left ventricular dysfunction (plasma cardiac output 3.46 +/- 1.08, range 1.2-5.7 L/min), and a close correlation between metabolic clearance rate and cardiac output was evident. Our data suggest that lungs do not extract, or extract only very small amounts, of labeled ANP administered iv to patients with different degrees of left ventricular myocardial involvement, and whole body extraction of labeled ANP remains relatively stable with the progression of disease, and the large reductions in clearance values observed in our patients can be ascribed mainly to the reductions in cardiac output.

Circulatory model in metabolic studies of rapidly renewed hormones: application to ANP kinetics

In an attempt to identify and quantify the sites of atrial natriuretic peptide (ANP) degradation, a new tracer experiment has been developed. 125I-ANP was injected as a bolus just upstream from the right atrium, and blood was sampled from two different sites (pulmonary artery and aorta) in eight cardiac patients. Data were analyzed using a physiologically based circulatory model consisting of three blocks in series (right heart, lungs and left heart, and periphery) supplied by the same flow (cardiac output, measured by thermodilution); the extraction coefficients of the three blocks and of the whole body could be determined from the areas under tracer concentration curves in plasma (AUCs). The values for AUCs (means +/- SD) were 64.8 +/- 9.4 and 65.5 +/- 10.7% dose.l-1.min-1 for pulmonary artery and aorta curves, respectively; the area under the pulmonary artery curve could be subdivided into the area under the first-pass curve (30.6 +/- 4.7% dose. l-1.min-1) and the area under the recirculating curve (34.0 +/- 7.7% dose.l-1.min-1). The metabolic clearance rate of 125I-ANP, computed as dose divided by the area under the recirculating curve, was 3.1 +/- 0.7 l/min, and the whole body extraction was 47.6 +/- 6.6%. In our patients with myocardial dysfunction, neither right heart block nor lungs and left heart block significantly extracted ANP, and periphery block accounted for almost all removal of the hormone from the blood.

Circulating levels of cardiac natriuretic peptides (ANP and BNP) measured by highly sensitive and specific immunoradiometric assays in normal subjects and in patients with different degrees of heart failure

Plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels increase in patients with heart failure with the progression of clinical symptoms and with the deterioration of hemodynamics; consequently, assay methods for these peptides may be useful in the follow-up of cardiac patients. Non-competitive immunoradiometric assay (IRMA) methods for ANP or BNP do not generally require preliminary extraction and/or purification of the plasma sample, and so may be more suitable than competitive immunoradiometric assay (RIA) methods for the routine assay of plasma peptide concentrations. We evaluated the analytical characteristics and clinical usefulness of two IRMAs for plasma ANP and BNP, to verify whether these methods may be considered suitable for the follow-up of patients with heart failure. Both methods are based on the solid-phase sandwich IRMA system, which uses two monoclonal antibodies prepared against two sterically remote epitopes of peptide molecule; the first antibody was coated on the beads solid-phase and the second was radiolabeled with 125I. Blood samples were collected from a brachial vein in ice-chilled disposable polypropylene tubes containing aprotinin and EDTA after the patient had rested for at least 20 min in the recumbent position. Plasma samples were immediately separated by centrifugation and stored at -20 C until assay. The IRMA methods showed a better sensitivity and a wider working range sensitivity (about 2 ng/l) than those of RIA methods. Moreover, the normal range found with these methods (ANP = 16.1 +/- 8.6 ng/l, 5.2 +/- 2.8 pmol/l, BNP = 8.6 +/- 8.2 ng/l, 2.5 +/- 2.4 pmol/l) was similar to that generally reported using the most accurate methods, such as the other IRMAs or RIAs, using a preliminary extraction and purification of plasma samples with chromatographic procedures. Our results obtained in patients with different degrees of heart failure indicate that plasma ANP and BNP increase with the progression of clinical symptoms (NYHA class) (ANOVA p < 0.0001). Indeed, circulating levels of ANP (R = -0.701, no. = 86) and BNP (R = -0.745, no. = 55) were significantly (p < 0.0001) and negatively correlated with the left ventricular ejection fraction values. Furthermore, a close curvilinear regression (R = 0.960, no. = 215) was found between ANP and BNP values, because plasma BNP progressively increases more than plasma ANP in patients with different stages of heart failure. In conclusion, IRMA methods are preferable for the measurement of plasma ANP and BNP for experimental studies and routine assay because they are more practicable, sensitive and accurate than RIA procedures. Finally, BNP assay appears to be better than ANP for discriminating between normal subjects and patients with different degrees of heart failure.

Ganciclovir therapy for cytomegalovirus-associated liver disease in immunocompetent or immunocompromised children

Ganciclovir therapy was given intravenously to 20 children with cytomegalovirus (CMV)-associated liver disease, of whom 6 were immunocompetent and 14 were immunocompromised (9 had AIDS and 5 had solid tumors). Immunocompetent children had isolated liver disease diagnosed at birth (4 children), or systemic congenital CMV infection including liver disease (2 children). Ganciclovir was used following two regimens: A) 5 mg/kg twice daily for 8 to 86 days (mean 21); B) 7.5 mg/kg twice daily for 14 days followed by 10 mg/kg three times weekly for three months. CMV infection was diagnosed by viral isolation, detection of viral antigens, and/or CMV DNA from blood and urine. All immunocompetent children had negative CMV culture and CMV DNA detection from blood and/or urine after 14 weeks of treatment. However, the three children who were treated with regimen B showed normal ALT levels at the end of the maintenance course, whereas the children who received ganciclovir with regimen A had normal ALT levels only after about 1 year. All children with tumors initiated regimen B, but only three, who had negative CMV detection and markedly decreased ALT levels, received full treatment; of the remaining two children, one recovered after only an initial course, and the other had therapy interrupted because of hepatic failure and died 9 days later. In contrast, the children with AIDS received several ganciclovir courses for different periods at the lower dosage: they generally improved during treatment but did not recover completely, and five children died with active CMV infections. Based on our study, CMV-associated liver disease can be efficiently treated with ganciclovir both in immunocompetent and immunodeficient children. However, a single ganciclovir course including a higher dosage and prolonged therapy appeared to be more effective than several courses with lower dosages.

Chemotherapy in low-grade astrocytoma management

The role of chemotherapy (CHT) in the management of low-grade astrocytoma (LGA) is still unclear. Nineteen children with nonresectable symptomatic LGA were treated with carboplatin (CBDCA) and etoposide (E). There were 15 newly diagnosed cases and 4 were relapses; 6 of the children were under 5 years old. In all children radiological evaluation by CT scan and/or MRI was performed after four courses of CHT. We observed complete response (CR)+ minor response (MR) in 37% of these cases and an improvement in neurological symptoms in 63%. Radiological evaluation performed in 6 patients who received CHT for longer periods (8-12 courses) showed major responses (CR+PR) in 67%. Local radiotherapy (40 Gy) was administered after CHT in 14 cases, but in 3 of these radiotherapy was delayed for 2 years. Five patients did not receive radiotherapy. The overall survival was 58% after an average follow-up of 60 months. All patients with brain stem tumors died of progressive disease even though 3 of these had shown clinical improvement after chemotherapy. In conclusion, in the treatment of nonresectable symptomatic LGA, CHT with CBDCA associated with E can be used to postpone radiotherapy in young children and even to avoid radiotherapy in some cases.

Acute effects of intravenous amiodarone on sulphate metabolites of thyroid hormones in arrhythmic patients

OBJECTIVES

Factors that contribute to the remarkably rapid decrease in serum T3 and increase in reverse T3 (rT3) levels during illness, fasting, or treatment with some drugs (e.g. amiodarone) are not clear. In order to understand better the effect of acute amiodarone administration on T3 metabolism, especially the sulphation pathway, we performed a prospective study in 8 arrhythmic in-patients treated with a loading dose of amiodarone.

DESIGN

Amiodarone was administered by i.v. infusion of 20 mg/kg/day on day 1 and 10 mg/kg/day on day 2, followed by 600 mg/day orally throughout the study. Two serum samples for amiodarone and hormone assays (thyroid hormones, TSH, and the sulphate metabolites of 3'-T1, 3,3'-T2, and T3) were collected before the start of therapy, every 12 h during the first 3 days of amiodarone administration, and then once a day for 2-10 days.

SUBJECTS

Eight patients (4 men and 4 women, aged 44-82 years), who were treated with amiodarone because of cardiac dysrhythmia, were enrolled in the study.

RESULTS

Serum concentrations of total T4 significantly increased in the last 3 days of the study (ANOVA, P = 0.0002). However, serum total T3 progressively and significantly decreased throughout the study (ANOVA, P < 0.0001). Serum free thyroid hormone concentrations (free T3 and free T4) did not significantly change during the study. Serum rT3 (ANOVA, P < 0.0001) and TSH (ANOVA, P = 0.0009) rapidly and progressively increased throughout the study. Starting from the first 24 h, serum concentrations of T3 sulphate (T3-S) significantly and progressively increased from (mean +/- SD) 0.057 +/- 0.029 nmol/l under basal conditions to 0.089 +/- 0.036 nmol/l after 5 days of amiodarone therapy (ANOVA, P = 0.0011). Since total T3 levels progressively decreased throughout the study, the ratio of the T3-S and total T3 values progressively increased from 4.8 +/- 2.7% under basal conditions to 10.6 +/- 7.3% after 5 days of amiodarone therapy (ANOVA, repeated measures, P < 0.0001). Basal serum concentrations of sulphate metabolites of T2 (T2-S, 2.22 +/- 1.7 nmol/l) and T1 (T1-S, 1.29 +/- 0.74 nmol/l) did not significantly change throughout the study.

CONCLUSIONS

Our data indicate that a loading dose of intravenous amiodarone in patients with cardiac dysrhythmias is followed by a very rapid and progressive increase in circulating T3-S levels, possibly due to an inhibition of type 1-iodothyronine de-iodinase. Since T2-S and T1-S, common final metabolites of the thyroid hormone sulphation pathways remained unchanged, our data suggest that the total amount of thyroid hormone degraded by sulphation pathways remains unaltered during amiodarone treatment. Finally our findings are compatible with the view that sulphation represents an important pathway for T3 metabolism in vivo in man.

Ceftriaxone as a single agent in empirical therapy of unexplained fever in granulocytopenic children with solid tumors

The optimal management of fever in granulocytopenic cancer patients remains controversial. Antibiotic monotherapy is increasingly an option for the initial empiric treatment of febrile granulocytopenic patients with solid tumors. Available data show that response to empiric therapy is often more related to disease classification (solid tumors vs. acute leukemia) than to the regimen used. In this study we based empiric monotherapy on the underlying disease (solid tumors) in treating 33 episodes of fever in 26 granulocytopenic children with cancer. We investigated the potential effectiveness of single daily doses of ceftriaxone administered empirically in febrile granulocytopenic children with solid tumors. Fever was treated successfully with ceftriaxone monotherapy in 91% (30/33) of febrile episodes. None of the patients died as a result of primary infection. These results suggest that empirical monotherapy with once-daily ceftriaxone is safe and effective. In addition, when compared with other extended-spectrum cephalosporins such as ceftazidime, once-daily administration of ceftriaxone reduces cost and patient inconvenience, allowing convenient parenteral therapy even on an outpatient basis.

Successful management with interferon alpha-2a after prednisone therapy failure in an infant with a giant cavernous hemangioma

A giant cavernous hemangioma of the left arm with severe thrombocytopenia and consumptive coagulopathy was observed in a neonate. Initial treatment with prednisone, platelet transfusions, and clotting replacement failed to control the bleedings. The child was then treated with daily subcutaneous infusions of interferon alpha-2a. Coagulopathy rapidly improved and transfusions were drastically reduced. The hemangioma regressed progressively and disappeared after 4 months of treatment.

Evidence that atrial natriuretic peptide tissue extraction is not changed by large increases in its plasma levels induced by pacing in humans

Atrial natiurectic peptide (ANP) is a cardiac hormone with a very short plasma half-life, which plays an important role in a variety of clinical conditions associated with an increase in pressure and/or volume overload on the heart. The MCR of the hormone is considered to represent a stable parameter, reflecting the uptake and degradation rate of ANP by the periphery, only scarcely affected by rapid oscillations of circulating levels. To evaluate the extent to which MCR is affected by rapid and large variations of circulating levels of the hormone, we measured MCR in five patients with different degrees of myocardial function (from normal to severely impaired), in whom changes in ANP levels were induced by atrial and/or ventricular pacing. Cardiac output was simultaneously measured by thermodilution to calculate whole body extraction of ANP. During constant i.v. infusion of [125I]ANP, the hormone MCR was determined both under basal conditions (at tracer equilibration, 20-30 min after the start of infusion) and during atrial and ventricular pacing. Pacing maneuvers, begun 50 min after the start of infusion, induced a marked and rapid increase in endogenous plasma ANP values in all patients (on the average, 3,7-fold compared to basal values; range, 1.8-5.68), whereas corresponding values of [125I]ANP only minimally changed. The MCR of ANP (3.62 +/- 1.06 L/min, mean +/- SD) slightly decreased (by repeated measures ANOVA, P = 0.0458) during atrial and ventricular pacing procedures (3.35 +/- 1.03 and 3.15 +/- 0.74 L/min, respectively), reaching a mean value of 88.7 +/- 9.0% compared to basal. The small decrease in MCR could be almost completely ascribed to hemodynamic factors; indeed, basal cardiac output (5.76 +/- 1.70 L/min) was found, on the average, to be slightly decreased during atrial and ventricular pacing (5.28 +/- 1.46 and 5.16 +/- 1.33 L/min, respectively), and so whole body extraction of the hormone, measured before pacing (50.0 +/- 12%), remains stable throughout the study period (50.4 +/- 10.6% and 49.6 +/- 10% during atrial and ventricular pacing, respectively). Our findings demonstrate that degradative mechanisms involved in ANP clearance are not saturable at least for acute elevations of ANP plasma levels up to 3-5 times the basal level.

Acute effects of amiodarone administration on thyroid function in patients with cardiac arrhythmia

Because little has been published on early effects of treatment with amiodarone on thyroid function, we studied serum total and free thyroid hormone, reverse T3, and TSH levels in patients with cardiac arrhythmias during the first 10 days of treatment with a loading dose of amiodarone by iv infusion. Twenty-four patients were enrolled in the study. A standardized loading regimen for the i.v. infusion of amiodarone was used. The protocol provided the i.v. infusion of 20 mg/kg per day on day 1, the i.v. infusion of 10 mg/kg per day on day 2, then 600 mg/day per os for 7-10 days, and finally, in patients chronically treated with the drug, the dose was gradually reduced to 400-200 mg/day per os. Total and free concentrations of T4 tended to progressively and significantly increase (P < 0.0001 repeated measures ANOVA) starting from the fourth day of therapy, whereas total T3 decreased from the second day progressively (P < 0.0001) throughout the study; free T3 did not significantly change. TSH levels early and significantly (P < 0.001, by ANOVA) increased throughout the study, starting from the first day of therapy and reaching at 10 days a value 2.7 times higher than the basal value. Reverse T3 levels progressively and significantly (after 2 days of treatment) increased and paralleled the TSH values, reaching at the 10th day a value about 2 times higher than basal value. In conclusion, our data suggest that after i.v. treatment with amiodarone: 1) TSH is the first hormone to change significantly followed by reverse T3, T4, and T3; 2) the progressive fall of T3 levels reflects an inhibition of the peripheral conversion of T4 to T3; 3) the observed later increase of total and free T4 levels may be explained by a contribution of direct thyroidal stimulation by TSH and/or by a reduction in T4 clearance.

Analytical performance and clinical usefulness of a commercially available IRMA kit for measuring atrial natriuretic peptide in patients with heart failure

We evaluated the analytical characteristics and clinical usefulness of a commercially available IRMA kit for measuring plasma concentrations of atrial natriuretic peptide (ANP) in healthy subjects and in patients with heart failure. The method uses two monoclonal antibodies prepared against sterically remote epitopes of the ANP molecule; the first antibody is coated on the solid-phase beads, and the second is radiolabeled with 125I. Fifty-nine healthy subjects and 77 patients with heart failure were studied. After subjects had rested 20 min in a recumbent position, blood samples were collected from a brachial vein into ice-chilled disposable polypropylene tubes containing aprotinin and EDTA. Plasma samples were immediately separated by centrifugation and stored at -20 degrees C until assay. The working range (CV &lt;15%) was 10-2000 ng/L. The detection limit (2.13 +/- 0.91 ng/L) was similar to those reported for other IRMAs but was much better than those of RIAs. For healthy subjects, the results of this method (18.0 +/- 10.6 ng/L, range 4.7-63 ng/L, median 16.7 ng/L, n = 59) were similar to those generally reported for the most accurate methods, i.e., those using preliminary extraction and chromatographic purification of plasma samples. Measured plasma ANP was significantly associated with the severity of clinical symptoms, i.e., NYHA class (ANOVA, P &lt;0.0001), and with the left ventricular ejection fraction (n = 62, r = 0.618, P &lt;0.0001). Patients with severe heart failure showed greatly increased values (NYHA III-IV: 257.4 +/- 196.6 ng/L, n = 23).

Analytical performance and clinical usefulness of a commercially available IRMA kit for measuring atrial natriuretic peptide in patients with heart failure

We evaluated the analytical characteristics and clinical usefulness of a commercially available IRMA kit for measuring plasma concentrations of atrial natriuretic peptide (ANP) in healthy subjects and in patients with heart failure. The method uses two monoclonal antibodies prepared against sterically remote epitopes of the ANP molecule; the first antibody is coated on the solid-phase beads, and the second is radiolabeled with 125I. Fifty-nine healthy subjects and 77 patients with heart failure were studied. After subjects had rested 20 min in a recumbent position, blood samples were collected from a brachial vein into ice-chilled disposable polypropylene tubes containing aprotinin and EDTA. Plasma samples were immediately separated by centrifugation and stored at -20 degrees C until assay. The working range (CV <15%) was 10-2000 ng/L. The detection limit (2.13 +/- 0.91 ng/L) was similar to those reported for other IRMAs but was much better than those of RIAs. For healthy subjects, the results of this method (18.0 +/- 10.6 ng/L, range 4.7-63 ng/L, median 16.7 ng/L, n = 59) were similar to those generally reported for the most accurate methods, i.e., those using preliminary extraction and chromatographic purification of plasma samples. Measured plasma ANP was significantly associated with the severity of clinical symptoms, i.e., NYHA class (ANOVA, P <0.0001), and with the left ventricular ejection fraction (n = 62, r = 0.618, P <0.0001). Patients with severe heart failure showed greatly increased values (NYHA III-IV: 257.4 +/- 196.6 ng/L, n = 23).

Normalization of peripheral thyroid hormone metabolism induced by successful chronic amiodarone treatment in patients with ventricular arrhythmias

Amiodarone, an antiarrhythmic agent, is also known to have important effects on the peripheral metabolism of thyroid hormones; the relationship between these two effects of the drug, however, is not well established. We tested the hypothesis that the antiarrhythmic effect of amiodarone might be mediated by its effect on the metabolism of thyroid hormones. Peripheral thyroid hormone metabolism was investigated using a double-tracer ([125I]-T4 and [131I]-T3) procedure in 10 normal volunteers and 10 euthyroid patients with complex ventricular arrhythmias before and during 6 months' amiodarone treatment. The underlying cardiac disease was coronary artery disease in four cases, dilated cardiomyopathy in three and idiopathic arrhythmias in three. In all but one patient with complex ventricular arrhythmias amiodarone treatment resulted in a reduction of > or = 80% of premature ventricular contractions and complete suppression of episodes of ventricular pairs or ventricular tachycardia. In all cases successful treatment with amiodarone was accompanied by normalization of all kinetic parameters: T4 to T3 conversion ratio and T3/T4 molar ratio of production decreased to mean values of 24.7 +/- 17.5% and 0.35 +/- 0.22% respectively, whereas T4 production rate increased (mean value 75.9 +/- 30.0 nmol day-1 m-2). Our kinetic data indicate that long-term therapy with amiodarone, when effective in suppressing cardiac arrhythmias, also reduces peripheral T4 to T3 conversion, hence restoring the normal peripheral thyroid hormone metabolic pattern. In conclusion, our study confirms that the antiarrhythmic action of amiodarone may be (at least partially) mediated by its action on thyroid hormone metabolism, and may justify the hypothesis that an altered peripheral metabolism of thyroid hormones may play a role in the pathogenesis of complex ventricular arrhythmias.

Acute enoximone effect on systemic and renal hemodynamics in patients with heart failure

Patients with heart failure generally show improvement in their clinical condition after enoximone infusion over the period of treatment; this effect cannot be ascribed only to the known hemodynamic action of this drug. Thirty-six patients (age range 44-82 years) with heart failure (NYHA class II-IV) underwent 48-hour enoximone infusion to study whether this prolonged improvement might depend on changes in systemic or renal hemodynamics or in neurohormonal balance. All patients underwent Swan-Ganz hemodynamic monitoring; renal plasma flow, glomerular filtration rate, plasma atrial natriuretic factor (ANF), and plasma renin activity (PRA) were all measured at baseline, at the peak of the enoximone action, and 48 hours after drug discontinuation. The main hemodynamic parameters were significantly improved during enoximone infusion and after drug discontinuation. The cardiac index basal value of 2.2 +/- 0.1 l/min/m2 increased to 3.1 +/- 0.1 l/min/m2 after 24-hour therapy (p < 0.01); similarly, pulmonary wedge pressure, mean pulmonary arterial pressure, and right atrial pressure decreased markedly (p < 0.01). Beneficial effects were also observed in renal hemodynamics; indeed, renal plasma flow (basal value 485 +/- 39 ml/min) increased significantly after 24-hour enoximone infusion (575 +/- 35 ml/min; p < 0.01), and this tendency was also observed 48 hours after drug discontinuation. No significant modifications were observed in plasma hormone data; however, the PRA plasma level had a tendency to decrease. We conclude that in patients with heart failure, enoximone infusion has a less marked effect on renal hemodynamics, but this is more lasting than systemic hemodynamic effects. The tendency of PRA to decrease (although not statistically significant), still detectable 2 days after treatment in the presence of steady high plasma ANF concentrations, may also contribute to the paradoxical longlasting benefit despite the short-lived improvement in systemic hemodynamics after brief cycles of enoximone infusion.

Preparation of mono-radioiodinated tracers for study of the in vivo metabolism of atrial natriuretic peptide in humans

In the present paper we evaluate the optimum chemical conditions for labelling atrial natriuretic peptide (ANP) and its metabolites and for preparing highly purified radiotracers which can be used for in vivo kinetic studies of ANP in humans. Synthetic alpha h1-28ANP and some hormone metabolites were iodinated with Na125I or Na131I by means of the lactoperoxidase (ANP) or the chloramine-T (ANP metabolites) technique. The biological activity of labelled ANP was tested by means of a binding study using mouse cardiac membranes. A high-performance liquid chromatography (HPLC) procedure was used to purify the labelled hormone and the principal labelled metabolites in venous plasma samples collected up to 50 min after the injection of 125I-labelled ANP from nine healthy men. The main ANP kinetic parameters were derived from the disappearance curves of the [125I]ANP, which were satisfactorily fitted by a biexponential function in all subjects. The main advantages of this tracer technique are: (1) high accuracy, allowing the identification of the metabolites produced in vivo under steady-state conditions after injection of the precursor (labelled hormone); (2) high sensitivity, allowing the detection of minimal quantities of metabolites (that cannot be identified on the basis of the integrated areas from the ultraviolet-absorbing peaks on HPLC); (3) high specificity, allowing the detection of possible in vitro artefactual generation of cleavage products of ANP using an internal labelled standard. Utilizing this tracer method, it was possible to estimate the principal parameters of ANP kinetics and also to plot the appearance curves of the labelled metabolites produced in vivo after the injection of the labelled precursor.

Alterations in metabolic clearance of atrial natriuretic peptides in heart failure: how do they relate to the resistance to atrial natriuretic peptides?

Deficiencies in activity of the atrial natriuretic peptide (ANP) system may be able to explain the disturbed electrolyte and fluid homeostasis occurring in chronic heart failure. Generally, in studies concerning the possible pathophysiologic role of ANP in heart failure, only the circulating levels of the hormone were measured. It has been shown, however, that plasma ANP levels exhibit marked variability attributable to the pulsatory pattern of secretion and to its very short plasma half-life. An evaluation of the main turnover parameters might represent a significant improvement in the assessment of the functioning of the overall ANP system. By using a tracer method, which does not alter the steady-state condition, a disturbed peripheral metabolism of ANP and a resistance to its biologic effects was demonstrated in patients with idiopathic dilated cardiomyopathy, even in those in the asymptomatic phase of the disease, showing ANP circulating levels, atrial pressure and volume, and cardiac index within the normal range. The altered degradation and distribution of ANP in patients with heart failure were demonstrated by a great increase in metabolic clearance (on average, 2.5-fold), production (on average, 6-fold), or both, and by a progressive reduction in the distribution spaces of the hormone when compared with normal subjects at the same sodium intake. The ratio between ANP disposal and the daily excretion of sodium (equal to the sodium intake in subjects at a strictly controlled sodium balance) may give a good index of the biologic activity (natriuresis) of the ANP system. Preliminary studies suggest that an index of biologic activity of the ANP system may be a useful tool for the comparison of the efficacy of different therapeutic strategies in heart failure. Indeed, after a 2-month treatment with an angiotensin-converting enzyme inhibitor, this index was returned to within the normal range, suggesting that the drug was able to "normalize" the peripheral distribution and degradation of the hormone in these patients. Although future studies in a large series of patients will be useful to assess this important issue, the setup of accurate methods able to evaluate the presence and degree of resistance to biologic activity of ANP may be a useful tool in the follow-up evaluation of patients with heart failure, and may pave the way for further progress in the knowledge of more general physiologic and pathophysiologic mechanisms of this important clinical condition.

Does chemotherapy have a role in low-grade astrocytoma management? A report of 13 cases

Surgery is the treatment of choice for low-grade astrocytoma while radiotherapy is carried out only when total resection is not possible. This study assessed the effectiveness of chemotherapy in nonresectable cases. Thirteen children with nonresectable astrocytoma were treated with carboplatin and etoposide and after four cycles the response to treatment was evaluated according to radiologic criteria. The results were: one with complete response (CR), three with minor response (MR), six with stable disease (SD), and three with progressive disease (PD). Moreover, in 77% there was an improvement in the neurologic picture. In particular, two cases with hypothalamic astrocytoma showed a regression of the diencephalic syndrome following chemotherapy. In six cases chemotherapy was carried out, at reduced dosage, after the first four cycles either because there was clinical improvement or because it was necessary to postpone radiotherapy in very young patients. After a follow-up period ranging between 11 and 63 months (average: 30 months), nine of the 13 patients are alive (69%) while four died of disease progression. Further studies would be useful to evaluate the role of chemotherapy in the management of low-grade astrocytoma.

Pressor, renal and endocrine effects of L-arginine in essential hypertensives

The pressor, renal and endocrine effect of the physiological precursor of endothelial derived nitric oxide, L-arginine was compared, with a substrate inactive on nitric oxide, hypertonic D-glucose, in hypertensive patients. Ten mild-moderate essential hypertensives were assigned to either L-arginine (n = 5) or D-glucose (n = 5). Substances were infused over 25 min at equiosmolal rates preceded and followed by saline infusion for 25 min. Blood pressure and heart rate were monitored at 3-min intervals, while hormonal and humoral variables, inulin and paraaminohippurate clearance and electrolyte excretion were measured at the end of each period under conditions of maximal diuresis. L-arginine and D-glucose increased serum osmolality comparably and caused similar haemodilution to that with control saline. During L-arginine infusion, systolic and diastolic blood pressure decreased by 16.6% and 11%, respectively, and recovered in the postinfusion period. Heart rate, plasma renin activity, and plasma noradrenaline did not change significantly. The percent blood pressure decrement induced by L-arginine was significantly greater than that by D-glucose. Glomerular filtration rate was stable and renal plasma flow was increased by both substances. However, natriuresis, kaliuresis and chloruresis were markedly stimulated only by L-arginine, which also promoted the development of systemic acidosis, possibly as a consequence of hydrochloridric acid generated during its metabolism. Circulating insulin, atrial natriuretic peptide, growth hormone and glucagon levels were increased and plasma aldosterone was unchanged during infusion of L-arginine. Insulin was stimulated and the other hormones inhibited during infusion of D-glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of different types of anti-aging dietary restrictions on age-related atrial natriuretic factor changes: an immunochemical and ultrastructural study

The effects of two types of anti-aging dietary restrictions restrictions-60% diet restriction (DR) and every-other-day feeding (intermittent feeding, IF)-on age-related changes in atrial natriuretic factor (ANF) metabolism were studied in male Sprague Dawley rats by standard radioimmunological procedures and transmission electron microscopy. Both diet restrictions decreased plasma ANP (atrial natriuretic peptide) levels significantly (12-month-old rats: ad libitum fed controls 96 +/- 17.3 pg/mL, IF 63 +/- 4.8 pg/mL, DR 74 +/- 14.4 pg/mL; 24-month-old rats: AL 109 +/- 6.3 pg/mL, IF 75 +/- 8.9 pg/mL, DR 65 +/- 9.1 pg/mL). Dietary restriction prevented the age-related increase in ANP concentration in both the right atrium (12-month-old rats: AL 0.25 +/- 0.033 microgram/mg, IF 0.22 +/- 0.023 microgram/mg, DR 0.30 +/- 0.044 microgram/mg; 24-month-old rats: AL 0.39 +/- 0.037 microgram/mg, IF 0.10 +/- 0.015 microgram/mg, DR 0.07 +/- 0.011 microgram/mg) and left atrium (12-month-old rats: AL 0.23 +/- 0.033 microgram/mg, IF 0.13 +/- 0.019 microgram/mg, DR 0.17 +/- 0.035 microgram/mg; 24-month-old rats: AL 0.44 +/- 0.037 microgram/mg; IF 0.07 +/- 0.009 microgram/mg, DR 0.07 +/- 0.011 microgram/mg). Endocrine cardiocytes of diet-restricted senescent rats could be readily distinguished ultrastructurally from cells of ad libitum fed controls due to a higher number of beta-atrial specific granules of lower electrondensity. In conclusion, anti-aging diet restriction regimens fully prevented the age-related increase in the hormone store in atrial tissue, and lowered plasma ANP levels.

[Pressor, renal and endocrine effects of systemic infusion of L-arginine in hypertensive patients]

In this study we compared the pressor, renal and endocrine effects of the physiological precursor of endothelial derived nitric oxide, L-arginine, with D-glucose, a substrate inactive on nitric oxide. Ten subjects with mild to moderate primary hypertension underwent infusion with either L-arginine (5 patients) or D-glucose (5 patients). The substances were infused over 25 min at equiosmolar rates, preceded and followed by a 25-min saline infusion. Blood pressure (BP) and heart rate were monitored at 3-min intervals; hormonal and humoral variables, inulin and para-aminohippurate clearance, and electrolyte excretion were measured at the end of each period at maximum diuresis. L-arginine and D-glucose brought about comparable increases in serum osmolality and similar hemodilution as compared with control saline. During L-arginine infusion, systolic and diastolic BP dropped by 16.6% and 11% respectively and recovered during the post-infusion period. Heart rate, plasma renin activity, and plasma norepinephrine did not change significantly. The percent BP decrease induced by L-arginine was significantly greater than that caused by D-glucose. Glomerular filtration rate remained stable, and renal plasma flow increased with both substances. However, only L-arginine stimulated markedly natriuresis, kaliuresis, and chloruresis. It also seemed to induce systemic acidosis, possibly as a consequence of hydrochloric acid generated during its metabolism. Circulating insulin, atrial natriuretic peptide, growth hormone, and glucagon levels increased, and plasma aldosterone remained unchanged during L-arginine infusion. During D-glucose infusion, insulin was stimulated and the other hormones were inhibited.(ABSTRACT TRUNCATED AT 250 WORDS)

Altered tissue degradation and distribution of atrial natriuretic peptide in patients with idiopathic dilated cardiomyopathy and its relationship with clinical severity of the disease and sodium handling

BACKGROUND

Atrial natriuretic peptide (ANP) has been suggested to play an important role in heart failure, preserving cardiorenal homeostasis through maintenance of the sodium balance and inhibition of the detrimental effects of the neurohormonal vasoconstrictor system. The current study was designed to investigate whether there is a disturbed renewal and distribution of ANP in patients with idiopathic dilated cardiomyopathy (IDC) with differing clinical severity of disease.

METHODS AND RESULTS

We used a tracer method to perform a cross-sectional study of 15 IDC patients with differing clinical severity (New York Heart Association functional class I to III), prospectively divided into two groups according to their functional class (group 1, classes I and II; group 2, classes II-III and III). Eleven normotensive, nonobese male volunteers also were studied as a control group. Main ANP kinetic parameters were derived from the disappearance curve of the labeled hormone after the bolus injection of [125I]-labeled ANP. A high-performance liquid chromatography technique was used to separate the radiolabeled hormone in each plasma sample. Patients in group 1 showed higher ANP metabolic clearance rate (MCR) (2731.9 +/- 726.2 mL.min-1.m-2) than patients of group 2 (1718.4 +/- 621.2 mL.min-1.m-2) and control subjects (1873.1 +/- 551.2 mL.min-1.m-2). ANP disposal (MCR) positively correlated with biological hormonal effect (urinary sodium excretion) both in control subjects and in patients. In IDC patients of both groups, however, MCR values were always higher (approximately doubled) than the values found in control subjects at the corresponding sodium excretion. This finding indicates that a reduced ANP biological activity is associated with hormone degradation in patients. Moreover, patients of group 2 showed significantly higher ANP production rates (395.6 +/- 183.8 ng.min-1.m-2) than group 1 (166.0 +/- 139.0 ng.min-1.m-2) and control subjects (130.7 +/- 105.4 ng.min-1.m-2) despite a marked reduction in sodium excretion. Patients with IDC showed a progressive reduction in the total distribution volume (group 1, 19.8 +/- 5.8 L/m2; group 2, 12.7 +/- 6.9 L/m2; control subjects, 27.0 +/- 11.6 L/m2) of the hormone; this probably was due to a reduction in exchanges of ANP with peripheral tissues.

CONCLUSIONS

Our study demonstrates a markedly altered degradation and distribution of ANP in patients with IDC, even in those at the early stage of clinical disease (classes I and II, group 1) who have ANP plasma levels in the normal range.

Cytomegalovirus-associated stage 4S neuroblastoma relapsed stage 4

Neuroblastoma is one of the most frequent solid tumors in childhood, rarely recurrent after five years from diagnosis. Cytomegalovirus (CMV), a major pathogen causing congenital birth defects and severe opportunistic diseases, has been shown to have teratogenic, immunodepressive and oncogenic properties. The case of a girl with stage 4S neuroblastoma diagnosed at three months and relapsed as stage 4 five years later is reported. In both circumstances, active CMV infection was revealed by positive CMV-specific IgM and IgA antibodies, CMV-DNAemia and CMV culture. At three months, the patient presented with subcutaneous nodules, hepatosplenomegaly and increased aminotransferase levels, and the opsolonus-myoclonus syndrome. Mental retardation developed later on. At 5 years, relapsed neuroblastoma was preceded by a mononucleosis-like syndrome concomitant with active CMV infection and decreased levels of immune cells and natural killer activity. Clinical, virologic, and immunologic findings suggest an immune-mediated pathogenic role for CMV in this tumor.

In vivo measurement of ANP overall turnover and identification of its main metabolic pathways under steady state conditions in humans

Using a tracer method, we evaluated, in vivo, the main turnover parameters and the main metabolic pathways of ANP in 10 normal subjects. HPLC was used to purify the labeled hormone and the principal labeled metabolites present in venous plasma samples collected at determined times after tracer injection. The main ANP kinetic parameters were derived from the disappearance curves of [125I] ANP, which were satisfactorily fitted by a biexponential function in all subjects. Newly produced ANP initially distributes in a large, plasma equivalent space (10.9 +/- 3.6 l/m2 body surface); the hormone rapidly leaves this space due to both degradation and to distribution in peripheral spaces. The mean residence time in the body (19.4 +/- 19.8 min) and the plasma equivalent total distribution volume (28.2 +/- 11.5 l/m2) indicate that ANP is also widely distributed outside the initial space in humans (circulating ANP is no more than 1/15 of the body pool). Metabolic clearance rate values were distributed across a wide range (from 740 ml/min/m2 to 2581 ml/min/m2, mean 1849 ml/min/m2), and were shown to strongly correlate (R = 0.962) with the daily urinary excretion of sodium. A complete separation of labeled ANP from its labeled metabolites was achieved by the HPLC technique; at least 3 different peaks due to labeled metabolites in vivo produced from the injected [125I]ANP1-28 were found. The first chromatographic peak eluted showed an identical elution time to monoiodotyrosine. At least two other peaks due to in vivo generated labeled metabolites were well identified in the chromatograms: one peak (coeluting with labeled COOH-terminal tripeptide, H-Phe-Arg-Tyr-OH) was eluted ahead and one (coeluting with labeled peptide fragments ANP7-28, ANP13-28, and ANP18-28) behind the elution peak of the labeled ANP. The peak of labeled tyrosine appearing in the plasma ranged between 3 and 5 min after tracer injection; the other two peaks of radioiodinated metabolites showed their highest activity in the first sample (1.5 min), suggesting an earlier occurrence of their peaks. These labeled metabolites seem to be intermediate peptides, between the intact circulating form of the hormone and the final labeled metabolite (tyrosine), which is the last amino acid of the peptide hormone, produced in vivo after injection of the tracer.(ABSTRACT TRUNCATED AT 400 WORDS)