One-year old mice were anesthetized by pentobarbital sodium (50–60 mg/kg body weight intraperitoneally; Nembutal; Abbott, Chicago, IL) and moved to a servo-controlled table kept at 37 °C. The left femoral artery was catheterized for measurement of arterial pressure, and a femoral venous catheter was used for infusion of volume replacement. Bovine serum albumin (4.75 g/dl of saline solution) was infused initially at 50 μl/min to replace surgical losses, and then at 10 μl/min for maintenance. Arterial pressure was measured via a pressure transducer in left femoral artery (Statham P23 DB, Gould, Valley View, OH), and renal blood flow was measured by a flowmeter (0.5 v probe; Transonic systems TS420, Ithaca, NY). To assess GFR, continuous injection of FITC-inulin infusion was performed at 1 mg.ml−1 and urine and blood collections were performed every 15 mn after equilibration. Inulin was measured by fluorometric method. GFR was calculated by measuring renal clearance of inulin over 3 period of time (formula UxV/P, U: urine concentration of inulin, P: plasma concentration of inulin and V: urine output).