Abstract
This study investigated the effect of chronic digitalis glycoside use on β-adrenergic sympathetic activities in heart failure. Twenty-two Japanese white rabbits were anesthetized by intravenous injection of chloral hydrate. Aortic regurgitation (AR) was produced by perforating aortic valves in 14 rabbits. Digoxin was given for 1 week to 7 rabbits with AR (AR+Dig) and saline to 7 rabbits with AR (AR+C). Sham operation was performed in the remaining 8 rabbits (S). The left ventricular end-diastolic pressure was higher in AR+C than S (p<0.05). It was lower in AR+Dig than AR+C (p<0.05). Cardiac output was lower in AR+C than S (p<0.05). There was no difference between AR+Dig and S. Both the left ventricular end-diastolic and end-systolic diameters were larger in AR+C (p<0.05) than S, but they were similar between AR+Dig and S. Plasma norepinephrine level was lower in AR+Dig than AR+C. Myocardial β-adrenergic receptors number determined by radioligand binding assay using 30-800pM 125I-iodocyanopindolol was lower in AR+C than S (28.8±7.9 vs. 69.9±12.3fmol/mg protein, p<0.05). It was higher in AR+Dig (39.9±9.8) than AR+C (p<0.05). Myocardial norepinephrine content was lower in both AR+C (p<0.05) and AR+Dig than S (p<0.05). Thus, digitalis glycosides exert favorable effects on β-adrenergic sympathetic activities in addition to the effects on hemodynamic variables in this animal model of heart failure.
