Reflex Diuresis during Tachycardia in the Dog

Renal function and systemic hemodynamics were studied during rapid atrial pacing in dogs with complete heart block and in control dogs with normal atrioventricular conduction. Rapid atrial pacing in dogs with complete heart block produced no significant change in urine flow, sodium excretion, or systemic hemodynamics. In contrast, rapid cardiac pacing in control dogs produced progressive increases in urine flow and sodium excretion and a decrease in arterial pulse pressure. Plasma antidiuretic hormone levels were not changed significantly by pacing in either group of dogs; likewise, mean atrial type B (volume) receptor discharge rate was not increased by pacing in either group. Rapid sequential atrioventricular pacing in three dogs with complete heart block did produce an increase in urine flow and sodium excretion, but rapid pacing of the atria alone in the same dogs did not cause a diuresis or a natriuresis. In other experiments on dogs with chronic sinoaortic denervation, rapid cardiac pacing caused no significant changes in urine flow or sodium excretion. Hence, the study provided no evidence to support the hypothesis that diuresis during tachycardia is elicited reflexly from atrial receptors. The data from dogs with sinoaortic denervation did suggest that receptors in the carotid sinus and the aortic arch participate in reflexly eliciting a diuresis during tachycardia.