Abstract
The isolated kidney handles haemoglobin in the same manner as the kidney in vivo. There is no excretion of haemoglobin when the haemoglobin-binding capacity is not saturated. When this is done and a free plasma haemoglobin level exists, the clearance of free haemoglobin had an average value of 3.24 ± 2.92 ml/min. The glomerular clearance ratio of haemoglobin averaged 0.10 ± 0.06. The calculated rate of tubular reabsorption of haemoglobin was 2.06 ± 3.12 mg/min. The graphic relationship between urinary excretion and plasma levels of free haemoglobin was linear. The theoretical plasma level above which haemoglobinuria occurred was 64.0 ± 35.2 mg%. These last two data are more suggestive of tubular reabsorptive activity than the calculated values.