THE EFFECT OF A SLIGHTLY ACIDIC SOMATOMEDIN PEPTIDE (ILAs) ON THE SULPHATION OF PROTEOGLYCANS FROM ARTICULAR AND GROWTH PLATE CHONDROCYTES IN CULTURE

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Abstract
Chondrocyte cultures were prepared from rabbit growth plate (GPC) and articular (ARC) chondrocytes. These 2 cells types have distinct morphological characteristics. The cells reached maximum numbers by days 10 and 21 for ARC and GPC, respectively. The proteoglycans (PG) contained in the cullular pool were extracted and purified by DEAE cellulose chromatography. The effect of a partially purified somatomedin peptide with insulin-like activity on [35S]sulfate incorporation into PG was evaluated. In both ARC and GPC a significant stimulation of [35S]sulfate uptake into PG subunits was obtained with 1 ng eq[equivalent]/ml of somatomedin peptide. In order to obtain the same stimulatory effect with porcine insulin, a 1000-fold greater concentration was required. The electrophoretic patterns of the PG subunits on acrylamide-agarose electrophoresis were identical on control incubations and after stimulation with the somatomedin peptide. These data apparently demonstrate in vitro biological activity of this peptide on well differentiated articular and epiphyseal growth plate chondrocytes in culture. These cultures appear to provide a sensitive biological assay for somatomedin peptides.