Right atrium and renal sodium excretion.

Inflation of a balloon in the right atrium of 13 dogs resulted in salt and water retention not attributable to changes in GFR, RPF, filtration fraction, mean arterial pressure, left atrial pressure, or renal venous pressure. The response to right atrial balloon inflation was compared with the renal effects of constriction of the abdominal aorta above the renal arteries and constriction of the ascending aorta. Neither procedure evoked the same response as balloon inflation. Results suggest that the decrease in mean arterial pressure which accompanies balloon inflation accounts for only part of the decreased salt and water excretion. There was no significant difference between the responses of denervated and intact kidneys to right atrial balloon inflation. A binary response to stretching of the right atrium is suggested, both components apparently involving hormonal mediation.