The effect of distending the atrial appendages on urine flow in the dog.

1. Distension of the atrial appendages resulted in a diuresis, an increase in the rate of Na(+) excretion and an increase in heart rate.2. Both the urinary and heart rate responses to distension of the appendages were either abolished or much reduced by crushing the bases of the appendages.3. The diuresis in response to distension of the atrial appendages is similar to that previously described in response to distension of the pulmonary vein-atrial junctions by Ledsome & Linden (1968).4. It is concluded that stimulation of nerve endings within the atrial appendages results in a reflex increase in urine flow and heart rate.