Mechanism of Autoregulation of Renal Blood Flow

Abstract

IT has been noted by Winton¹ and has since been confirmed many times^2–5, that the renal vascular resistance is not constant but increases with increasing arterial pressure in the range 80–120 mm. mercury mean pressure. The phenomenon does not depend on an intact nerve supply to the kidney but occurs in the denervated, perfused kidney. The autoregulation of renal blood flow has been considered attributable either to an active vasomotor process^3–5 or, in some recent work, to a flow-dependent separation of plasma from red cells in the renal circulation. The first of these theories appears to have been developed only by the process of elimination, and the second appears no longer tenable in the light of experiments by several groups^5–7. The œdematous kidney displays a high resistance to flow which probably results from compression of vessels by extravascular fluid. This factor has not been considered important in the function of kidneys subjected to normal arterial and venous pressure, since measurements of renal tissue pressure⁵ indicated that it does not vary directly with renal vascular resistance.