Nitric oxide production in chondrocytes following culture with elevated glucosamine and subsequent challenge by IL-1β. Articular chondrocytes from rats were seeded into 20 flasks, which were divided into four groups. Glucosamine was added to a final concentration of 20 mM to two of the groups. Six hours later, 10 ng/ml IL-1β was added to one group receiving glucosamine and to one previously untreated group. NO production was assessed by measurement of nitrite in the conditioned media from the four respective groups: untreated control, glucosamine (Gln) alone, IL-1β alone, and glucosamine with IL-1β. Results are expressed in μM nitrite, each bar representing the mean of five assays. Error bars represent one standard deviation. *P < 0.05 versus glucose control.