An extract of cardiac atrial tissue, when injected intravenously into anaesthetized rats, caused a large and rapid increase in renal excretion of sodium chloride. 2. The renal response to atrial extract was associated with increases in total and medullary blood flow in the kidney, as measured by microsphere and albumin uptake methods, respectively. 3. The data suggest that these changes in renal haemodynamics may contribute to, but are unlikely to be the complete cause of, the natriuresis and chloriuresis following injection of atrial tissue extract.
