The experiments were carried out to determine whether localized pulmonary arterial distension caused changes in the renal excretion of water and solutes. 2. When pulmonary arterial pouch pressure was maintained constant at low pressure 0.5-1.6 KPa (4-12 mm Hg) urinary excretion of sodium remained relatively constant over a period of 110 min. 3. Increasing pulmonary arterial pouch pressure by 3.6 KPa (27 mm Hg) did not cause changes in systemic pressure or solute excretion. Increasing pulmonary arterial pouch pressure by 6.7 KPa (50 mm Hg) increased systemic arterial pressure and caused a small increase in sodium excretion. 4. In dogs prepared in similar fashion but with one kidney totally isolated and perfused at constant pressure, increasing pulmonary arterial pouch pressure by 9.3 KPa (70 mm Hg), increased systemic arterial pressure, osmolal clearance and solute excretion from the intact kidney. There were no changes in urinary excretion from the isolated perfused kidney. 5. The increase in solute excretion associated with pulmonary arterial distension is most likely to be due to haemodynamic effects on the kidney possible accompanied by changes in renal nerve activity.
