Granulocytes utilize different energy sources for movement and phagocytosis

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Abstract
Granulocytes depend on anaerobic glycolysis for the energy required for chemotaxis, phagocytosis, and microbial killing. Two potential sources of the needed glucose are available: exogenous glucose and intracellular glycogen. These studies demonstrate that chemotaxin-induced movement of granulocytes induces accelerated uptake of exogenous glucose while phagocytosis does not, presumably utilizing instead the relatively slow process of glycogenolysis. As measured by incorporation of extracellular radiolabeled hexoses [1-14C]glucose or [3H]deoxyglucose), the soluble chemotaxin-aggregants of granulocytes, nF-met-leu-phe, CSades arg, bacterial filtrate, or arachidonic acid all augment transmembrane hexose uptake. This insulin-like activity closely parallels the dose-related effects of these agents on induction of granulocyte aggregation and chemotaxis. Insulin, itself, affects glucose transport minimally and mainly at supraphysiologic concentrations. In contrast, phagocytic stimuli fail to enhance hexose uptake at all, despite stimulating catabolism of glucose, which in turn is probably generated by glycogenolysis. These data show that granulocytes, whose motile function occurs in glucose-rich milieu, alter in tandem their cellular glucose uptake with their movement response. For phagocytosis, which often occurs in hypoglycotic, purulent exudates, granulocytes depend on stored energy supplies—probably glycogen. This coordination may be crucial in supporting granulocyte antimicrobial activity during acute inflammation.