Cardiac-renal-neural reflex plays a major role in natriuresis induced by left atrial distension.

Abstract

The role of cardiac-renal-neural reflex in the natriuresis induced by left atrial balloon inflation was investigated in conscious dogs. Female mongrel dogs were assigned randomly to 1) sham-operated (n = 8), 2) cardiac-denervated (n = 6), and 3) renal-denervated (n = 8) groups. The dogs were chronically instrumented with a bipolar stainless steel wire electrode for measurement of renal sympathetic nerve activity (RSNA). Balloon inflation induced a step increase in left atrial pressure (Pla) by 7.7 +/- 1.7 mmHg, a step decrease in RSNA (-66.6 +/- 5.5%), and concomitant increases in urine flow (441 +/- 142%), osmolal excretion (60 +/- 12%), and sodium excretion (300 +/- 69%) in sham-operated dogs. Renal denervation abolished the diuresis and natriuresis during balloon inflation. Chronic cardiac denervation abolished also the diuresis and natriuresis in the face of a similar increase in Pla. RSNA did not change significantly throughout the experimental period in cardiac-denervated dogs. It is concluded that a sustained reduction of RSNA originating from left atrial mechanoreceptors plays a major role in the natriuresis during left atrial distension in conscious dogs.