Haptoglobin Metabolism in Polycythemia Vera

1. Turnover studies with ¹²⁵I-labeled haptoglobin (Hp) were performed in 7 patients with polycythemia vera, 2 patients with erythrocytosis of unknown etiology, and 2 control subjects.

2. The T½ of plasma radioactivity was shortened in 6 of the 7 patients with polycythemia vera; 3 of these had diminished plasma Hp levels but lacked other evidence of hemolysis.

3. The fractional catabolic rate exceeded 40 per cent/day in all subjects with a shortened half-time of plasma radioactivity.

4. Increases in the fractional catabolic rate were not accompanied by increases in Hp turnover (mg./kg./day), suggesting that accelerated Hp catabolism per se does not provide a stimulus to Hp production.

5. It is concluded that patients with polycythemia vera catabolize Hp more rapidly than nonpolycythemic subjects, possibly because of increased formation and removal of the haptoglobin-hemoglobin complex.