Intrarenal Distribution of Blood Flow during Elevation of Ureteral Pressure in Dogs

The 85 Kr method was used to determine the effect of elevated ureteral pressure on total cortical and outer medullary nutrient renal blood flow of pentobarbital-anesthetized dogs. Increased ureteral pressure during mild saline diuresis resulted in increased total nutrient blood flow from 316 to 402 ml/100 g/min. Autoradiographs demonstrated that the increased blood flow is confined to the renal cortex and that juxtamedullary cortical and outer medullary flow is unchanged. Elevated ureteral pressure decreased total renal blood flow from 473 to 381 ml/g/min during copious mannitol diuresis. This is due at least partly to decreased cortical blood flow; we were unable to measure juxtamedullary cortical plus outer medullary blood flow during mannitol diuresis. Isolated renal arteries relaxed when placed in a physiologic salt solution containing 70 mM mannitol. Renin release is increased during elevation of ureteral pressure. We concluded that the mechanism for increased renal blood flow during ureteral occlusion selectively involves the nutrient circulation of the renal cortex.