Inactivation of arginine-vasopressin by the isolated perfused rabbit kidney

The ability of the kidney to extract (inactivate and excrete) argininevasopressin (AVP) from the blood was studied in the isolated perfused rabbit kidney. AVP was added to the blood reservoir to give an initial approximate concentration of 100 μu./ml plasma and samples were taken simultaneously from the arterial and venous side at 5, 15, 30 and 45 min. The AVP concentration in the plasma samples was determined by bioassay in the water-loaded, ethanol-anaesthetized rat. The clearance (extraction ratio x renal plasma flow) of AVP from the blood was concentration-dependent. The average extraction ratio ranged from 0·25 at levels of 100 to 44 μu./ml plasma and 0·42 at levels of 44 to 19 μu./ml plasma. The excretion of AVP in the urine was 23% and 29% respectively of the calculated filtered load, in two isolated perfused kidneys, indicating tubular reabsorption and/or tissue inactivation of the filtered hormone.