Possible role for chondroitin sulfate in urolithiasis: in vivo studies in an experimental model

The effect of chondroitin sulfate upon the growth of calcium oxalate crystals was measured in vivo by using an experimental model in rats. Adult male Wistar rats were treated by chronic i.p. injections of chondroitin sulfate solutions (1, 5 or 10 mg in 0.3 ml of saline, every 2 days). This treatment led to a dose-dependent increase in the urinary chondroitin sulfate concentration. Urolithiasis was induced by the introduction of a calcium oxalate seed into the bladder of the animals. Urine samples were collected and the calculi formed were removed after 42 days. The chondroitin sulfate concentration have decreased in the lithiasic urines, as compared to controls and higher chondroitin sulfate doses correlated with larger calculi. The presence of chondroitin sulfate in the matrices of stones obtained from chondroitin sulfate-treated animals suggested that there was some adsorption of chondroitin sulfate on to the growth sites of the calcium oxalate crystals. In contrast to the chondroitin sulfate effect observed in vitro, which inhibits the growth of calcium oxalate crystals, our results suggest that in vivo chondroitin sulfate promotes the growth of stones in the urinary tract.