In vivo and in vitro effect of bacterial endotoxin on erythroid precursors (CFU-E and ERC) in the bone marrow of mice.

Erythropoietin injection raised within 24 hr. the number of CFU-E in the femoral marrow of polycythemic mice by 837 percent. Endotoxin given at 0 to 24 hr. before erythropoietin nearly abolished this CFU-E increase. Endotoxin in the culture medium did not inhibit erythroid colony formation, but in vivo endotoxin suppressed erythropoietin-induced differentiation of proerythroblasts from their precursors. Endotoxin thus suppresses marrow erythropoiesis either by inhibiting transformation of erythroid precursors into CFU-E or by causing the disappearance, perhaps by emigration, of CFU-E from the marrow.