THE DEMONSTRATION AND LOCALIZATION OF RENAL TUBULAR REABSORPTION OF HEMOGLOBIN BY STOP FLOW ANALYSIS *

Abstract

A study of renal tubular reabsorption of free hemoglobin was made in the dog utilizing the technique of stop flow analysis. A reduction in hemoglobin concentration in trapped urine was found, indicating tubular reabsorption. The sequential changes in concentration observed indicated reabsorption in a proximal site in the nephron,in an area coextensive with paraaminohippurate secretion. Similar changes were elicited by transient occlusion of the main renal artery. Reabsorption during both ureteral and arterial occlusion was attributed to an intrinsic tubular mechanism, the effects of which were enhanced by the static conditions imposed. The failure to observe reabsorption by conventional free flow methods is attributable to a small reabsorptive capacity.