Response of hepatic hematopoiesis to whole body irradiation

Extensive hepatic erythropoiesis, granulocytopoiesis and megakaryocytopoiesis occur in adult mice given methylcellulose (MC). This appears to be a compensatory response to MC induced hemolytic anemia and thrombocytopenia. The present study was undertaken to evaluate the effects of whole body irradiation (WBI) upon established hepatic hematopoiesis (HH) as well as its effect when given before the induction of HH. Established hepatic erythroid and granulocytic foci were significantly decreased 24 hours after 100 or 300 rads. The DO for erythroid and granulocytic foci was 107 +/- 10 rads and 95 +/- 20 rads respectively, similar to those reported for murine marrow and spleen cell CFUS. Megakaryocytes were more radioresistant, gradually declining over 7 days to 50% of control values following 100 rads and with a DO of 347 +/- 7 rads; suggesting a differential radiation sensitivity compared to erythroid and granulocytic foci. WBI, 100 and 300 rads, given before MC failed to prevent subsequent development of HH although both marrow and spleen responses were reduced. Hepatic granulocytic foci and marrow peroxidase positive cells were reduced by such treatment while erythroid and megakaryocytic foci were similar to controls. This suggests that irradiation damaged stem cells responded to MC with increased erythropoiesis and megakaryocytopoiesis at the expense of granulopoiesis.