Effects of endotoxin and extracts of pregnant mouse uterus on the recovery of hemopoiesis after 5-fluorouracil.

A single injection of endotoxin, 4 hours after administration of 150 mg/kg of 5-fluorouracil (5-FU), stimulated the recovery of bone marrow hemopoietic cells that form colonies in spleen (CFU-S) or in culture (GM-CFC), of erythropoiesis, and of platelet production. Corynebacterium parvum injections had similar effects. Endotoxin-free extracts of tissues (from pregnant mouse uterus, placenta, and embryo) which have a high content of the factor(s) capable of stimulating growth of GM-CFC in vitro also stimulated recovery of CFU-S and GM-CFC when given in single injections 4 hours after 5-FU. A striking effect of both endotoxin and tissue extracts was the acceleration of the regeneration of a particular subclass of granulocyte macrophage progenitors, those capable of forming large colonies (greater than 0.25 mm) in agar. The results indicate that recovery of hemopoiesis after depression by 5-FU can be stimulated not only by injection of bacterial products, but also by injection of endotoxin-free tissue extracts which contain high levels of hemopoietic regulators.