Differential in vitro sensitivity of marrow erythroid and granulocytic colony forming cells to chloramphenicol

The effects of chloramphenicol (CAP) and thiamphenicol (TAP) on mouse and human in vitro erythroid (CFU-E) and granulocytic (CFU-C) colony forming units have been studied. Both drugs inhibited CFU-E growth in a concentration-dependent, stereospecific, manner. Complete inhibition of human CFU-E growth was observed at a CAP concentration of 10 microgram/ml while a concentration ofer 50 microgram/ml was required to inhibit CFU-C growth. Furthermore, whereas the inhibition of CFU-C growth could be blocked in vitro by high colony stimulating factor concentrations, inhibition of CFU-E growth was not affected by increased erythropoietin (ESF) levels. The lack of protection by ESF may account for the apparent vulnerability of erythroid cells to CAP in vivo.