Urinary clearance of angiotensin II in Pekin ducks

To quantify the renal excretion of angiotensin II (AII) in birds, synthetic AII was intravenously infused into conscious Pekin ducks at rates of 5, 15 and 45 ng/kg/min for 30 min and the relationships between plasma and urine AII concentrations were monitored by radioimmunoassay. The infusions of AII produced dose-dependent elevations in the plasma concentrations of the hormone, however, urinary concentrations and excretion rates did not change significantly from the basal values of 11.6 +/- 1.2 pg/ml and 4.3 +/- 1.0 pg/min, respectively. The metabolic clearance rate of AII remained constant at each infusion dose (approximately 120 ml/min/kg). The urinary clearance rates (< 0.3 ml/min/kg) indicated that the fraction of AII cleared from the blood via the urine was less than 0.2%. Clearly, excretion of intact AII via this route is not a quantitatively important means of elimination for this hormone in birds.