Renal blood flow as influenced by changes in arterial, venous, and ureteral pressures

Abstract

The mechanism of renal autoregulation is unclear. The subject of the present investigation was the mechanism of autoregulation of blood flow in the intact (in situ) kidney. The left kidney of the anesthetized dog was exposed via a flank approach. Renal venous outflow was measured during control periods and after separate elevations of renal artery pressure, renal vein pressure, and ureteral pressure. Extravascular pressure was estimated by obtaining values of (a) deep vein pressure, (b) needle pressure, and (c) elevations in large vein pressure and ureteral pressure resulting in significant decreases in renal blood flow. Increases in renal artery pressure result in elevations of extravascular pressure which compress the renal vasculature. Increases in renal vein and ureteral pressures do not decrease renal blood flow until approximating or exceeding resting tissue pressure. Results from experiments with carotid artery occlusion indicate that extrarenal humoral influences may be superimposed on the autoregulatory phenomenon.