The 2'-5' adenylate (2-5A) system in erythropoiesis.

: The trimer and tetramer core forms of 2'-5' Adenylate (2-5A) were tested in vitro for their effect on mouse liver CFU-E. Both forms of 2-5A core partially inhibited the CFU-E response to erythropoietin when given as a single dose at time 0 hours. Approximately 25% fewer colonies were seen after 2-days growth following exposure of the CFU-E to 0.1 mM 2-5A core. A 0.01 mM concentration of exogenous 2-5A core was not inhibitory. Endogenous 2-5A synthetase activity was assayed in spleen cell lysates from mice made anemic by several injections of phenylhydrazine. This method of treatment stimulated erythropoiesis, and this was directly correlated with an increase in the rate of enzyme activity measured by lysate conversion of 14C-ATP to 2-5A (our in press data suggests that the same may occur with hypoxic stimulation). This suggested to us that endogenous 2-5A synthetase and its 2-5A, a known inhibitor of DNA synthesis and protein synthesis, may help to regulate some of the late events in erythropoiesis.