Oxidation of glucose by mouse peritoneal macrophages: a comparison of suspensions and monolayers

Macrophages, when maintained in vitro, take up glucose from the medium and oxidize it to CO2. The rate of oxidation of glucose varies considerably, depending on the physical state of the cell preparation. Cells in suspension oxidize glucose at a level six-fold that of cells in monolayers. The differences cannot be attributed to change in the rats of transport of glucose. On the other hand, an increase in intracellular glycogen (about three-fold) and free glucose plus glucose-6-P (many-fold) was found in the cells prepared as monolayers. During subsequent incubation with glucose-14C, this could be the cause of an isotope dilution effect and could explain the lower production of 14CO2 by the adherent cells. Since oxidation of glucose-1-14C to 14CO2 is used by many investigators to indicate the functional state of macrophages, we suggest close attention be paid to the system used, i.e., monolayers vs. suspensions.