The range of renal blood flow for renal autoregulatory adjustments in resistance.

The study was designed to determine the range of renal blood flow over which autoregulation occurred. Pressure-flow relationships were obtained in the left kidney over a wide range of perfusion blood flow. Renal vascular resistance showed sigmoidal changes with changing renal blood flow over the range of 0.3 to 6.3 ml/min.g kidney wet weight. This curve shows two definite points of inflection at renal blood flows of 2.3 and 3.7 ml/min.g. Once renal blood flow rises above the normal range, renal vascular resistance changes hyperbolically with decreases in renal blood flow. We conclude that (1) the range of blood flow for autoregulatory adjustments in resistance is between 2.3 and 3.7 ml/min.g, and (2) the autoregulatory mechanism can be easily impaired by increasing renal blood flow far above the upper limit of the range.