Atrial distension of isolated rabbit hearts and release of atrial natriuretic factor

Interventions that increase atrial pressures in humans or laboratory animals release atrial natriuretic factor (ANF) into the circulation. We studied the relation between distension of the right or left atrium and release of ANF in retrograde-perfused isolated rabbit hearts. A fluid-filled balloon within the right or left atrium was inflated to a mean pressure of 5, 10, 15, or 20 mmHg, and ANF in the cardiac effluent was measured by radioimmunoassay. The slope of the regression line relating ANF release to atrial distending pressure was steeper for the left than right atrium (P less than 0.001), indicating that, at comparable increases in mean pressures, the left atrium releases more ANF than does the right atrium. Left atrial tissue concentration of ANF was greater than right atrial (1.58 +/- 0.15 vs. 1.05 +/- 0.09 micrograms ANF/mg protein, P less than 0.01). In contrast to previous studies showing right atrial dominance in rats, the left atria of isolated, perfused rabbit hearts contain more ANF and release more in response to atrial distension.