Kidney pressures after temporary renal artery occlusion in the rat

Acute kidney failure was produced in the anesthetized rat by 1 h of complete renal artery occlusion. Kidney function was studied either immediately after release of the occlusion or 1 day later using clearance, micropuncture, histological, and nephron dissection techniques. Polyfructosan clearance was decreased to 5% of normal after temporary occlusion. Proximal tubular pressure (PTP) averaged 13-14 mmHg in normal kidneys, 39 mmHg immediately after release of unilateral occlusion, 19 mmHg 1 day after unilateral occlusion, and 25 mmHg 1 day after bilateral occlusion. The increased PTP reduces the glomerular filtration rate (GFR). Glomerular capillary pressure, estimated from the sum of the stop-flow and arterial plasma colloid osmotic pressures, was not decreased after temporary ischemia. Single-nephron GFR, measured without intratubular pressure control, was only slightly below normal 1 day after bilateral occlusion. Most distal tubules from ischemia-damaged kidneys contained hyaline casts. Tubular obstruction is a major factor in this model of acute kidney failure.