Effects of Perfusion Pressure and Renal Flow upon Albumin Excretion in Isolated Perfused Kidneys

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Abstract
To explore the effects of renal hemodynamics upon urinary albumin excretion, sequential changes in perfusion pressure and/or flow were performed in isolated perfused rat kidneys. Elevation of perfusion pressure from 90 to 130 mm Hg increased renal flow from 4.89 .+-. 1.1 to 54.3 .+-. 1.4 ml/min and glomerular filtration rate (GFR) from 0.37 .+-. 0.03 to 0.81 .+-. 0.06 ml/min (p < 0.001). Despite more than a doubling in GRF, albumin excretion remained unchanged (from 252 .+-. 53 to 167 .+-. 36 .mu.g/min, p not significant), resulting in a descreased fractional clearance of albumin (.theta.) from 0.009 .+-. 0.002 to 0.004 .+-. 0.005 ml/min (p < 0.01). To dissociate the effects of flow from those of pressure, angiotensin II was infused to decrease renal flow from 49.9 .+-. 0.6 to 38.7 .+-. 0.6 ml/min (p < 0.001), while keeping perfusion pressure constant at 96 1 mm Hg. Although GFR was essentially unchanged (from 0.59 .+-. 0.02 to 0.65 .+-. 0.05 ml/min, p not significant), albumin excretion increased from 68 .+-. 8 to 151 .+-. 21 .mu.g/min (p < 0.001) and .theta. rose from 0.002 .+-. 0.000 to 0.005 .+-. 0.001 (p < 0.02). Whole kidney hemodynamics acutely affect renal excretion of albumin in isolated kidneys.