2-Deoxy-D-glucose uptake by rat granular pneumocytes in primary culture.

Uptake of 2-deoxy-D-glucose (DG) was investigated with rat granular pneumocytes isolated in primary culture. Cells attached to flasks were incubated in Minimal Essential Medium usually containing 5 mM DG in place of glucose. Uptake of DG increased progressively with time of incubation and approached a plateau value of 35-40 mumol/10(6) cells at 60 min. Uptake increased as a function of external DG concentration with half-maximal uptake at approximately 2.0 mM DG. DG uptake was inhibited by the presence of glucose, alpha-methylglucoside, phlorizin, ouabain, or sodium-free medium. After 60 min incubation, approximately 20% of total intracellular DG was in the free form, and the calculated mean intracellular concentration of free DG (n = 4) was approximately twice the external concentration. Phosphatase activity was indicated by increase in free DG and efflux from cells after removal of external DG. In comparison with pneumocytes, uptake of DG by alveolar macrophages showed different kinetics, and intracellular free DG did not exceed the extracellular concentration. These findings indicate that type II cells take up DG by a sodium-dependent, carrier-mediated transport process that results in accumulation of free sugar against a concentration gradient.