The separation of renal activity from lung and from the venous effluent from perfused lungs.

1. Antidiuretic and salt-retaining activity has been separated from cat and ox lung, and from the venous effluent of blood-perfused cat lungs, by acetone extraction, gel filtration, partition and thin-layer chromatography.2. The chromatographic properties of the renally active substance from lung and from pulmonary venous blood are similar.3. The renal actions of these substances, demonstrable in vivo and in the isolated organ, are characterized by reduction in the excretion of water and Na. Renal blood flow, glomerular filtration rate and the urinary Na/K are not significantly affected.4. Concentrations of the lung substance which equate with angiotensin II-val(5)-amide in reduction of urinary Na in rats during water diuresis and under alcohol sedation do not raise the mean arterial pressure of the anaesthetized rat nor contract the superfused rat colon. At these dose levels angiotensin II is markedly vasopressor and contracts the superfused rat colon.