Role of Red Blood Corpuscles in Regulation of Renal Blood Flow and Glomerular Filtration Rate

Abstract

Renal blood flow was measured as a function of arterial red cell concentration in acute experiments on anesthetized cats breathing oxygen. Renal blood flow changed only slightly when the arterial red cell concentration was varied over the range 20–55%, despite large changes in the viscosity of blood as measured in a glass tube or in a perfused hindleg. When the red cell concentration was progressively reduced below 20%, however, the blood flow (measured at constant pressure) increased greatly, despite the fact that blood viscosity changes very little in this range of cell concentrations. Renal blood flow and glomerular filtration rate (creatinine clearance) were measured as a function of arterial pressure at normal and at very low arterial red cell concentrations. Autoregulation of both renal blood flow and filtration rate was partly or wholly abolished at low red cell concentrations. Autoregulation returned when cells were restored. The experimental results are explicable in terms of the cell-separation theory of renal hemodynamics (1). According to this theory the renal blood flow and glomerular filtration rate are largely controlled by the efficiency of separation of red cells from plasma in the interlobular arteries. Many observations which were previously attributed to differential changes in afferent and efferent arteriolar resistance can be equally well accounted for in terms of the cell-separation theory.