[Incorporation of labeled cortisol into different types of connective tissue]

The properties of early (BFUen) and late (CFUen) erythropoietin-independent progenitors were studied in bone marrow plasma clot cultures of mice. Syngeneic serum was used as a stimulant of colony formation. It was revealed that serum from polycytemic mice did not alter the efficacy of cloning the erythroid progenitors. Varying effects produced on erythropoiesis in vivo did not significantly change the number of CFUen and BFUen, with the exception of posttransfusion polycytemia where the number of CFUen showed a statistically significant rise. Assessment of radiosensitivity and proliferative activity of the erythroid progenitors showed that for CFUen D0=206 rad and n=1.3; for BFUen D0=118 rad and n=1.4; the proportion of proliferating CFUen was 42% +/- 12.5 and that of BFUen 46% +/- 4.5. The data obtained confirm the hypothesis of the erythropoietin-independent nature of the erythroid progenitors expressed under the culture conditions used.