Destruction of Immature Erythrocytes Measured by Bilirubin Excretion

The change in radioactivity of bilirubin with time was measured after injection of glycine 2-¹⁴C into rats with a bile fistula. The total radioactivity and specific activity of bilirubin were abnormally high in rats of which erythropoiesis was increased following hemorrhage.

When the newly formed erythrocytes labeled with glycine 2-¹⁴C in the peak of reticulocytosis were transfused into rats with a bile fistula, the excretion of labeled bilirubin increased rapidly.

The amount of newly formed erythrocytes destroyed within 7 days after transfusion into normal animals was calculated as 4.4 per cent of the total erythrocytes formed during maximum reticulocytosis and 1.1 per cent of those formed in the normal state in Sprague Dawley rats, while in the Wistar strain, the values were 13.4 per cent and 2.2 per cent, respectively.

These results provide direct evidence for increased production of short-lived erythrocytes during enhanced erythropoiesis, and the hemolysis of newly formed erythrocytes soon after they reach the general circulation may contribute to the production of shunt bilirubin.