Blood Destruction in the Polycythemia Induced by Hypoxia

The hemoglobin catabolism during the development and during the disappearance of polycythemia induced by hypoxia was studied by measuring the total circulating hemoglobin and the daily bile pigment excretion in bile-fistula dogs before, during, and after prolonged periods of exposure to 20,000 feet simulated altitude.

1. The inscreased erythropoiesis during the first weeks of altitude exposure was accompanied by a signiflcant increase in bile pigment output. The possible sources of this pigment excretion are discussed.

2. The life spans of the red cells during altitude exposure was found to be about 115 days. No differences were observed in the longevity of the cells in animals at ground level and at altitude.

3. The normalization of the polycythemic blood levels took place within six to eight weeks after returns to ground level, and was achieved by the combined effect of a depressed erythropoiesis and of an increased blood destruction. The increase in red cell destruction observed under these conditions demonstrates the existence of an "active" mechanism of blood destrunction by which the organism is able to destroy normal blood cells before their life span is exhausted. This increased red cell destruction, however, accounted for only 21 to 39 per cent of the hemoglobin which disappeared from circulation after return to ground level. The major part of the normalization of altitude polycythemia was brought about by a temporary depression of erythropoiesis which was estimated to amount to 30 or 40 per cent of the normal cell production in the six weeks after the discontinuation of the altitude exposure.