Studies on the nature of the plasma erythropoietic factor (S).

Abstract

Abstract 1.1. The erythropoiesis stimulating factor in boiled "anemic" plasma extracts is ether soluble. 2.2. When given to the normal rat, this factor produces erythrocytosis due to microcytes, reticulocytosis, and myeloid erythrocytic hyperplasia. There are no associated increases in hemoglobin or hematocrit values. 3.3. Ether extracts of whole unmodified "anemic" plasma evoke an identical response in the recipient. 4.4. Current data indicate the existence of more than one plasma factor. One is heat stable, ether soluble, and most likely a lipid. It stimulates erythroblastic division but not hemoglobin synthesis. Another is relatively thermolabile, insoluble in ether, and probably protein in nature. It appears to augment hemoglobin production. 5.5. The conflicting experimental findings that have been reported by different investigators studying the humoral regulation of erythropoiesis are reviewed. It is suggested that these apparent discrepancies are due to the presence of two plasma erythropoietic factors which differ in nature and mode of action.