Atrial stretch increases sodium excretion independently of release of atrial peptides

The effects of atrial distension on plasma atrial natriuretic factor and renal salt and water excretion were studied in normal dogs and in cardiac-denervated dogs. In five conscious normal dogs, elevation of left atrial pressure (7.8 Torr) consistently increased plasma concentrations of radioimmunoassayable atrial natriuretic factor (riANF), urine flow, and sodium excretion. Elevation of right atrial pressure (3.5 Torr) in the same five dogs also consistently increased riANF, but sodium excretion and urine flow did not increase. In four conscious cardiac-denervated dogs, elevation of left atrial pressure (9.2 Torr) consistently increased riANF, but urine flow and sodium excretion did not increase. Because atrial distension increased plasma riANF in each of the three types of experiments, but urine flow and sodium excretion increased in only one type, we conclude that atrial natriuretic peptides are not responsible for the diuretic and natriuretic responses elicited by left atrial distension. It is conceivable, of course, that atrial peptides released during atrial distension may act synergistically with other changes evoked by atrial distension and thereby contribute to the natriuresis elicited by left atrial stretch. However, the increase in plasma riANF during atrial distension appears to be incapable of independently increasing salt and water excretion in the conscious dog.