THE RELATION OF RENAL BLOOD FLOW TO EFFECTIVE ARTERIAL PRESSURE IN THE INTACT KIDNEY OF THE DOG

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Abstract
The typical trend relating renal blood flow to mean effective arterial blood pressure in the intact kidney is an exponential curve concave toward the pressure axis which (by extrapolation) it intercepts at an avg. value of 14 mm. Hg. This value becomes an acceptable figure for indicated yield pressure for blood flow through renal vessels. In interpreting the relationship of blood flow to pressure, flow is decreased at first only by small decrements as pressure is decreased from an avg. of 116 mm. Hg. With further reduction in pressure the gradient of the curve becomes steeper, with larger decrements in flow. At lowest pressures, flow virtually ceases. Analysis of renal vascular resistance shows that resistance to flow is quite large at the higher pressures, becomes less as pressure falls, and increases again at the lowest pressures. The higher resistance at maximal pressures is thought to be the result of glomerular filtration, increasing the viscosity of the blood. At minimal pressures the increased resistance may* be the result of plastic flow of the blood. An explanation of the autonomous control of renal blood flow, based on physical factors, is advanced.