The influence of the polar anastomotic vessels on autoregulation and the urinary excretion of water and sodium by perfused cat kidneys.

1. Cat kidneys have been perfused from pump-oxygenator and from heart-lung circuits.2. Kidneys perfused from the pump-oxygenator circuit excreted more water and sodium and showed higher values for sodium: potassium in urine than kidneys perfused from heart-lung circuits. Renal plasma flow and the clearances of creatinine and p-aminohippuric acid were similar for preparations perfused by the two different methods.3. Dorsal and ventral polar anastomotic vessels appeared to communicate directly with sheaves of vasa recta in the kidneys of young cats through interlobar vessels.4. Ligature of these polar anastomotic vessels impaired autoregulation of blood flow in perfused cat kidneys.5. Open drainage from these polar vessels during perfusion increased the rates of excretion of water and sodium.6. Histological preparations made from kidneys perfused from pump-oxygenator and from heart-lung circuits for periods of 5-6(1/2) hr showed that the nephrons remain undamaged. The diameters of the tubules correlated with the rates of urine flow immediately before fixation.