Evaluation of the effects of antiarthritic drugs on the secretion of proteoglycans by lapine chondrocytes using a novel assay procedure

Abstract

A new method is described for separating free 35SO4-- from 35SO4 labelled proteoglycans synthesized by rabbit articular chondrocytes cultured in the presence of excess 35SO4--. The procedure uses the low solubility product of barium sulphate to remove, by precipitation, free 35SO4-- from 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 effects 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 μg/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 μg/ml but had no effect at lower concentrations. Inhibition of secretion was strongest with indomethacin and diclofenac at 50 and 100 μg/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 μg/ml. Sodium pentosan polysulphate, but not glycosaminoglycan polysulphate ester, showed inhibitory activity at 50 and 100 μg/ml.