Lymphokine-induced uptake of [14C]glucosamine, [14C]glucose, and [3H]leucine by macrophages

Lymphokine-activated (LK+) and control (LK-) macrophages were cultured for 66 h and then pulsed with [14C]glucosamine. Uptake of [14C]glucosamine was greater in LK+ than in LK- cultures. If, after 66 h, the medium was replaced with fresh medium and then pulsed with either [14C]glucose or [14C]glucosamine, the uptake of isotope was greatly reduced compared to cultures with no change of medium. However, uptake of both radiolabeled substances was still found to be greater in LK+ cultures than in LK- cultures. Although uptake of both substances was enhanced by lymphokines, the uptake kinetics of each isotope was different. Under similar conditions the uptake of [3H]leucine was not enhanced by lymphokine activation. These data are interpreted to mean that LK+ macrophages are metabolically stimulated and utilize more glucose and glucosamine. The difference in kinetics implies a different utilization by macrophages for each substance.