Transport and metabolism of glucosamine by cultured Novikoff rat hepatoma cells and effects on nucleotide pools.

As estimated from initial uptake rates, the uptake of glucosamine-l-14C by cultured Novikoff rat hepatoma cells in glucose-free basal medium follows normal Michaelis-Menten kinetics, with an apparent Km of about 20 mM. Since glucosamine is not accumulated by the cells against a concentration gradient, the main mode of uptake is by facilitated diffusion, but other evidence indicates that glucosamine also enters the cells by simple diffusion. Glucosamine is probably transported by the same system as glucose. Glucosamine transport is competitively inhibited by glucose and, to about the same extent as is glucose transport, by Persantine and Cytochalasin B. Since neither of the two inhibitors affects the phosphorylation of glucose or glucosamine by cell-free preparations, we suggest that transport is a reaction distinct from phosphorylation. At low concentrations of glucosamine in the medium (0.1 mM and below), the inhibition of glucosamine transport into the cell by glucose, Persantine, or Cytochalasin B results in a proportional decrease in glucosamine incorporation into macromolecules. When cells are incubated with low concentrations of glucosamine-14C, most of the acid-soluble