Presence of An Active Erythropoietic Factor (Erythropoietin) in Plasma of Rats after Prolonged Cobalt Therapy. ∗

Abstract

Summary

1) Plasma was obtained from hemorrhagic anemic rats and from rats injected with cobalt for 26 days for determination of erythropoietic activity. Cobalt concentration of plasma from cobalt treated rats was lowered to normal levels by dialysis against isotonic phosphate-cyanide solution of pH 7.5. The level of cobalt in plasma was determined by modification of the nitroso-R-salt method. 2) Plasma to be injected was concentrated 6.6 times in vacuo. The erythropoietic activity was tested, using reticulocyte changes as index of activity, in hypophysectomized rats injected subcutaneously with 1 cc of concentrated plasma for 3 consecutive days. Reticulocyte counts were made 24 and 48 hours after end of injections. Plasma from anemic animals caused increase of reticulocytes to 61.5 and 151% (24 and 48 hours respectively) above values obtained from injections of plasma from normal rats. Injections of “cobalt treated” plasma increased the level of circulating reticulocytes to 36.4 and 54.5% above values obtained from injecting plasma from normal rats for similar time intervals, and demonstrates that erythropoietic activity of plasma is increased in rats receiving prolonged cobalt therapy, and that the activity is not due to increased levels of cobalt.