Effect of cortisol in vitro on haemoglobin synthesis by mouse foetal liver

In cultures of foetal mouse liver, collected at various gestational days, the effect of cortisol was investigated on 59Fe uptake into haemoglobin heme and also on the differentiation of the erythroid stem cells or ERC (erythropoietin-responsive cells) into erythroblasts under the action of erythropoietin. Addition of cortisol to the culture medium did not modify in any way the responsiveness of the cell system to erythropoietin but exerted a sustaining action on the rate of haemoglobin synthesis during the second half of the incubation period. This action was restricted to cultures of 15- to 16-day livers and was particularly obvious in erythropoietin-supplemented samples. This selective effect of cortisol likely concerns only the later types of erythroblasts since after 24 h of incubation the polychromatophilic or orthochromatic stages predominate respectively in samples with, or without, erythropoietin. The timing of these results is discussed in the light of previous findings observed in vivo by other authors in the foetal rat.