Retrograde infusion of blood into a pulmonary vein promotes natriuresis in anaesthetized dogs.

Retrograde infusion of blood into a pulmonary vein raised the pressure by 0.5-1 kPa in the cannulated vein. There were no changes in heart rate, arterial blood pressure, left atrial pressure, right atrial pressure or the pressure in the other pulmonary veins. The rise in pulmonary venous pressure was associated with an increase in urinary sodium concentration and excretion. However, there was no change in urine volume. The natriuresis was abolished by cooling the vagi to 9 degrees C. It is argued that receptors up-stream in the pulmonary veins themselves may be involved in the increase in sodium excretion that follows a rise in left atrial pressure.