Granulocyte release by endotoxin in normal and irradiated mice

Abstract

Granulocyte mobilization brought about by S. typhosa endotoxin was studied in normal and irradiated mice in which initial counts ranged from 100 to 5,000/mm³ in tail blood and 100 to 1,800/ mm³ in orbital sinus blood. In irradiated mice, 4–11 days after exposure, late occurrence of granulocytosis and absence of a peak at beginning of mobilization are presumably related to marrow aplasia. A transitory increase in percentage of young forms and a thinning of cellular population density in femoral marrow indicates an early contribution from this source. Although counts from tail blood during peak mobilization were extremely high compared to counts from orbital sinus blood, a few hours later mobilization ratios in both tail and sinus blood were the same for irradiated and nonirradiated mice, without regard to initial count. (Mobilization ratios were about twice as high in tail blood as in sinus blood.) A multicompartment system is proposed which is compatible with constant mobilization ratios. Under this model, when rate of delivery from marrow is slow relative to rates of transfer between compartments, ratios of compartment sizes become a constant independent of time and initial conditions and dependent only on magnitude of rate constants.