Presence of toxic substances which inhibit erythropoiesis in serum of uremic nephrectomized rabbits.

The presence of toxic substances which inhibit erythropoiesis in uremic sera is still undetermined. We examined the effect of aceton-methylalcohol extracts of serum of nephrectomized rabbits with uremia on the erythropoiesis. The percentage red cell iron utilization was markedly reduced in nephrecto mized rabbits with uremia. The administration of aceton-methylalcohol extracts of uremic rabbit serum resulted in a marked decrease of percentage red cell iron utilization in rats which fasted for 32 hours. However, the administration of aceton-methylalcohol extracts of normal rabbit serum did not result in any decrease of percentage red cell iron utilization in fasting rats. The administra tion of uremic extracts caused a marked shortening of the reticulocyte life span in colehicinized rats. The percentage of erythroblasts labeled with H3 thymidine in vitro was markedly reduced in uremic nephrectomized rabbits. The administration of uremic extracts resulted in a decrease of the in vivo incorporation of H8-thymidine in erythroblasts with their increased abortion in rats which starved for 32 hours. These results demonstrate the presence of toxic substances which inhibit erythropoiesis in uremic rabbit serum.