Cardiac and Noncardiac Atrial Natriuretic Factor (ANF) Biosynthesis and Storage and Plasma ANF in the Rat Model of Chronic Ventricular Dysfunction

Abstract

To evaluate the role of atrial natriuretic factor (ANF) in chronic heart failure (HF), the biosynthesis and storage of ANF in cardiac and noncardiac tissues and the level of plasma ANF were measured in rats exhibiting minimal [2-fold rise in left ventricular end diastolic pressure; myocardial infarct (MI) scar length, 25% left ventricle (LV)] and moderate-severe (3-fold rise in left ventricular end diastolic pressure; decreased contractility (dp/dtmax); MI scar length, 47% LV) chronic HF 30 and 60 days after coronary arterial ligation. In rats with moderate-severe HF (30 days post-MI), the cardiac ANF mRNA concentration (determined by dot blot analysis) increased in three heart chambers [LV, 6-fold; left atria (LA), 3-fold; right ventricle (RV), 2-fold], cardiac immunoreactive ANF (IRANF; determined by RIA) concentration increased on the left side (LV, 7-fold; LA, 33%), but was unchanged (RV) or reduced on the right side (right atria, 33%), and plasma IRANF increased 3-fold above sham control values. Excluding the LV (used for MI scar length), the pattern and magnitude of change in ANF mRNA concentration in moderate-severe HF at 60 days were similar to those at 30 days; the cardiac IRANF concentration at this time was the same (LA) or less than (RV, 66%) sham values, and plasma IRANF increased 6-fold above respective sham values. Generally, the changes in the concentrations of cardiac ANF message and peptide and levels of circulating ANF peptide were smaller in rats with minimal HF. The minute quantities of ANF mRNA and IRANF detected in noncardiac tissues (lung, liver, pituitary, aortic arch, brain, kidney, and salivary gland) were unaltered by HF. These findings show that chronic HF, as defined by hemodynamic and histological measurements, specifically and continuously stimulates atrial as well as ventricular ANF biosynthesis; levels of plasma and cardiac ANF are increased early in HF, but with time are subject to modulation. The cardiac ANF system is the prime locus for the effects of HF, as noncardiac ANF biosynthesis and storage are undisturbed by chronic HF.