Abstract
Summary
1) Some patients with aplastic anemia had exceptionally high levels of erythropoietic activity in plasma. The urine of these patients was assayed, and in some it was equally as potent as the plasma. As little as 1 ml daily for 14 days of untreated urine from such a patient produced a significant polycythemia in normal adult rats. When a concentrate of such urine, prepared by ultrafiltration, was injected at a dose equivalent to 30 ml daily for 14 days into normal adult rats, a polycythemia was produced which exceeded that resulting from exposure to a simulated altitude of 15.000 feet for the same period of time. 2) The high potency of such urine has allowed its assay in normal rats. This finding, together with the easy availability of urine and the efficiency of ultrafiltration as a method for preparing concentrates of urinary erythropoietic activity, should allow for a more rapid investigation of the chemistry and biology of this factor.
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