The sensitivity of cells to the inhibition of N- glycosylation by glucosamine was correlated to glucosamine toxicity. (A) Western blot analysis of DU145, A2058 and PC-3 cells cultured with the indicated concentrations of glucosamine (mM) for 4 h. Whole-cell lysates were subjected to immunoblotting using antibodies specific for clusterin as N-glycosylation marker. The open arrow indicates the molecular mass of N-glycosylated clusterin and the filled arrow indicates N-glycosylation deficient clusterin. Each blot is a representative of three independent experiments. (B) The viability of DU145, A2058 and PC-3 cells cultured in the presence of the indicated concentration (mM) of glucosamine for 48 h. The viability of cells was measured by cell counting using the colorimetric Janus green whole-cell stain method. The results were present as mean+/-SD of four independent experiments.