The experiments were performed on male, Sprague-Dawley rats (Mus, Biberach, Federal Republic of Germany), weighing 170 to 275 g, which had been given free access to a standard pellet diet (1324, Altromin, Lage, Federal Republic of Germany) and tap water. The animals were anesthetized with 100 to 120 mg of mactin per kilogram of body wt (Byk, Gulden, Constance, Federal Republic of Germany) and placed on a heated operating table adjusted to maintain rectal temperature at 37 to 38 C. The trachea was cannulated and a catheter was placed in the right jugular vein for the infusion of 0.25 to 0.4 ml/hr per 100 g of body wt of isotonic saline, containing 1 to 2 1sCi/ml of 3H-methoxy-inulin (New England Nuclear, Dreieich, Federal Republic of Germany) in the clearance experiments. A catheter was also placed in the right femoral artery for measuring blood pressure (BP) and collecting blood sam-ples. The left kidney was exposed through a flank incision, was dissected free of perirenal fat and, in those kidneys to be made ischemic, a portion of the renal artery was dissected free from the renal vein. The renal artery was completely occluded with a non-traumatic clip for 45 mm and the covered kidney was kept warm either with a lamp or by dropping warmed mineral oil on it. Following ischemia, the kidney was immobilized in a cup (Lucite®) and bathed with mineral oil heated to 38 C; the ureter was cannulated close to the renal pelvis to allow collection of timed urine samples.

Renal function was measured in control kidneys and 1, 3, and 18 hr after reintroducing blood flow to the ischemic kid-ney. The weight of the drained right and left kidney of each ani-mal was determined in a control group and in another group 3 hr after ischemia of the left kidney. Morphological studies were