Use of 3H-glucosamine and 35S-sulfate with cultured human chondrocytes to determine the effect of glucosamine concentration on formation of chondroitin sulfate.

OBJECTIVE: To determine whether addition of glucosamine will stimulate synthesis of chondroitin sulfate by cultures of human chondrocytes, and to compare the relative contribution of endogenous glucosamine to exogenous glucosamine in forming chondroitin sulfate.
METHODS: Cultured human chondrocytes were incubated with (35)S-sulfate and various amounts of glucosamine to determine whether any incremental formation of chondroitin (35)S-sulfate occurred. Similarly, chondrocytes incubated with variable concentrations of (3)H-glucosamine were examined to determine how much the incorporation into (3)H-chondroitin sulfate was diluted by provision of endogenous glucosamine that was derived by metabolism from glucose.
RESULTS: No stimulation of chondroitin (35)S-sulfate synthesis was found at concentrations of glucosamine up to 1 mM, a concentration of (3)H-glucosamine well above the concentrations that could be presented to cartilage after ingestion of advertised amounts of glucosamine. Furthermore, there was significant dilution of exogenous glucosamine by endogenous glucosamine provided by metabolism from glucose.
CONCLUSION: The results indicate that exogenous glucosamine does not stimulate chondroitin sulfate synthesis by human chondrocytes. Furthermore, the cells have the capacity to form amounts of glucosamine from glucose far in excess of that provided from exogenous sources, except at concentrations greater than could possibly be achieved with oral administration of glucosamine.