The glomerular clearance and renal transport of hemoglobin in adult males.

The demonstration by Polonovski, Jayle, Boussier and Badin (1, 2) that certain plasma proteins have the property of binding extracorpuscular hemoglobin has led to recent re-evaluation of the mechanisms of renal transport of hemoglobin in the dog (3) and in man (4). Lathem (4) showed that circulating extracorpuscular hemoglobin is bound quantitatively to the a2-globulin, haptoglobin. By utilizing the infusion of autogenous hemoglobin solution, Lathem demonstrated that in man: 1) no unbound hemoglobin is found in the circulation until the plasma hemoglobin-binding capacity is saturated; 2) hemoglobinuria does not occur unless unbound hemoglobin is present in the circulation; and 3) neither protein-bound hemoglobin nor methemalbumin appears in the urine during hemoglobinuria. From the relationship between changing concentration of unbound hemoglobin in the plasma (APfree Eb) and urinary excretion rate (ZAUfree HbV) an estimate of the glomerular clearance of hemoglobin (CGfreeHb) may be obtained. As defined by Lathem (4), glomerular clearance of free hemoglobin =AUfree HbV/APfree HbPrevious studies from this laboratory (5, 6) have demonstrated a sytematic decrease in glomerular filtration rate, effective renal plasma flow and various tubular transport maxima with age. A progressive loss of whole nephrons with aging has been proposed (5). Little is known of the effect of aging on the permeability characteristics of the glomerular membrane. Everitt (7) has reported a tenfold increase in the daily excretion of urinary protein nitrogen from youth to senility in the rat. Studies in mice by Thung (8) have demonstrated both qualitative and quantitative changes in proteinuria in older animals, .but the relationship of these changes to glomerular perme-