Effects of naloxone on the secretion of atrial natriuretic factor and of noradrenaline during hydric load in moderate chronic heart failure

BACKGROUND. The aim of our study was to evaluate the effects of endogenous opioids on the secretion of atrial natriuretic factor (ANF) in moderate chronic heart failure (HF). METHODS. We evaluated the effects of i.v. volume load (NaCI 0.9% at 0.25 ml/Kg/min for 60 minutes) on heart rate (HR), on mean arterial pressure (MAP) and on the plasma levels of β-endorphin (β-end), met-enkephaline (Met-enk), dynorphine (Dyn), atrial natriuretic factor (ANF) and noradrenaline (NA) in 10 patients (age 58±9) with HF in NYHA class II (group I) and in 8 healty control subjects (age 54±10) (group II). The volume load was repeated after at least three days during infusion of naloxone (2 μg/Kg/min), evaluating the above mentioned hemodynamic and hormonal parameters. RESULTS. The acute volume expansion caused an increase in ANF concentration (from 51.7±19.7 to 67.4±36.9 pg/ml; p<0.05) and in β-end (from 11.9±5.3 to 16.6±7.5 fmol/ml; p<0.05), in group I. In group II an isolated increase in ANF was observed (from 14.1 ±7.8 to 21.9±7.9 pg/ml; p<0.02). No significant changes were detected for HR, MAP, Dyn, Met-enk and NA. In group I the percent increase of ANF is less than in group II (30 vs55%; p<0.05). The volume load infused during naloxone Infusion caused a significant increase in HR (from 73±6 to 78±9 bpm; p<0.05) and in NA (from 311 ±123 to 415±142 pg/ml; p<0.05) in group I. In group II, an increase in ANF was detected (from 13.8 ±6.0 to 23.6±5.0 pg/ml; p<0.01). CONCLUSIONS. Our data suggest that in moderate HF β-end stimulates the secretion of ANF and inhibits the activity of the sympatho-adrenergic system during acute volume expansion.