Evaluation of the effects of antiarthritic drugs on the secretion of proteoglycans by lapine chondrocytes

A new method is described for separating free 35SO4from 35SO4 labelled groteoglycans synthesised by rabbit articular chondrocytes cultured in the presence of excess 4 The procedure uses the low solubility product of barium sulphate to remove, by precipitation, free 35SO4from culture medium. Optimum recovery of 35so4 labelled proteoglycans was achieved after papain digestion to release 35SO4-glycosaminoglycans, and addition of chondroitin sulphate before the precipitation step. Using this assay, we studied the effect of six drugs-indomethacin, diclofenac, sodium pentosan polysulphate, glycosaminoglycan polysulphate ester, tiaprofenic acid, and ketoprofen-on the secretion into the medium of labelled proteoglycans by lapine chondrocytes. The six drugs were tested at 0< 1, 1, 10, 50, and 100 I.g/ml over four consecutive 48 hour culture periods. A consistent concentration-response pattern was found for the four non-steroidal anti-inflammatory drugs (NSAIDs) studied. Generally they inhibited proteoglycan secretion at 50 and 100 [ig/ml but had no effect at lower concentrations. Inhibition of secretion was strongest with indomethacin and diclofenac at 50 and 100 ig/ml. In contrast with the NSAIDs studied, the two sulphated polysaccharides (sodium pentosan polysulphate and glycosaminoglycan polysulphate ester) at low concentrations increased proteoglycan secretion by chondrocytes, with maximal stimulation occurring at 1 [ig/ml. Sodium pentosan polysulphate, but not glycosaminoglycan polysulphate ester, showed inhibitory activity at 50 and 100 pg/ml.