Intrarenal venous and tissue pressure and autoregulation of blood flow in the perfused kidney

Abstract

In experiments on the isolated perfused dog kidney, intrarenal venous pressure, tissue pressure and renal blood flow were measured while renal artery pressure was progressively increased over the autoregulatory range. Results indicate that tissue pressure is closely correlated with simultaneously measured intrarenal venous pressure. As the arterial pressure is increased, the coincident rise in interstitial pressure tends to obliterate intrarenal veins, which however are maintained patent by the upstream arterial pressure head. Intrarenal venous pressures corroborate tissue pressure measurements on the basis that the venous transmural pressure is found to be small regardless of the magnitude of the venous intraluminal pressure. Increases in ‘over-all’ vascular resistance (RA/F) occur in all kidneys, while increases in ‘intrarenal’ resistance (RA-RV_int./F; RA-TP/F) are small or absent. Calculated intrarenal resistance is of primary importance in renal hemodynamics since it is derived from the measured pressure drop from renal artery to large intrarenal veins including essentially all of the kidney substance.