Distribution of blood flow in the dog kidney

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Abstract
While 15 μm microspheres (Ms) in principle provide a measure of glomerular flow, uptake rate of inert diffusible tracers indicates “effective” or “nutrient” flow, i.e. essentially postglomerular capillary flow. Paired measurements of glomerular and postglomerular flow were made in tissue samples from outer, middle and inner cortex (C1, C2, C3) and medullary zones. After a control Ms injection, renal vascular conductance (RVC) was altered in one kidney whereupon a second Ms injection was made, immediately followed by infusion of the125I‐iodoantipyrine and tritiated water. RVC was increased maximally byLa. infusion of acetylcholine with and without reduced renal arterial pressure, whereas moderate vasodilation was produced by lowering renal arterial or rising ureteral pressure. RVC was reduced by i.a. or i.v. infusion of angiotensin II. Within a mean RVC range of 50 to 180% of control the fractional distribution of zonal postglomerular flow remained unaltered, in agreement with previous results obtained from local H2gas desaturation rate. Glomerular flow was about 20% higher in C1, equal in C2and 40% lower in C3as compared to postglomemlar flow in control kidneys. This disparity nearly disappeared during maximal vasodilation and tended to increase during vasoconstriction. The results might suggest a variable net postglomerular effective flow in radial direction through the renal cortex. Alternatively, the fractional redistribution of Ms might reflect a variable degree of Ms skimming at the afferent arteriolar inlets along the interlobular arteries.