Enhanced uptake of 3H-glucosamine by macrophages stimulated by macrophage-activating factor

The enhanced uptake and incorporation of 3H-glucosamine by guinea pig peritoneal exudate macrophages stimulated by macrophage-activating factor (MAF) were studied. MAF was produced by concanavalin A- (Con A) stimulated lymphocytes. Two systems were developed to assay this phenomenon, one using microtiter plates, the other using suspension cultures. Enhanced uptake of 3H-glucosamine by macrophages was found after 48-hr incubation in microtiter plates and after 24 hr in suspension cultures. Increased uptake of 14C-glucose and 3H-galactose was also observed under these conditions. The enhanced uptake of 3H-glucosamine was markedly reduced or abolished by the addition of glucose to the cell cultures or by replacement of the medium with fresh medium before pulsing with labeled sugar. These observations indicate that the mechanism of enhanced uptake reflects in part increased glucose utilization by the stimulated macrophages.