Abstract
In the course of studies on somatomedin activity we have noted that normal rat serum routinely inhibited 3H-thymidine incorporation by rat or porcine cartilage while, at the same time, it stimulated sulfate incorporation. Human serum did not show this selective inhibition for 3H-thymidine incorporation in the somatomedin bioassay system. With porcine cartilage we found a serum dose response of 3H-thymidine inhibition at serum concentrations from 0.625% to 40%. Inhibitory activity was stable to repeated freezing and thawing, storage in a partially purified state at 4° for two weeks, and heating at 90° for 30 min. at pH 5.5. Inhibition occurred in cartilage of fasted, hypophysectomized or control rats. With different durations of pre-incubation and/or incubation rat serum inhibited 3H-thymidine uptake in all samples, but human serum stimulated 3H-thymidine uptake over long periods. Untreated serum retained its inhibitory activity after prolonged dialysis; addition of ammonium sulfate at 10% saturation or greater and dialysis resulted in loss of all serum activity. Significant purification of the factor was achieved by gel filtration on Bio-Gel P-200. The active fraction had an absorption maximum at 260nm consistent with the presence of nucleic acid; there were no absorption peaks at 230nm or 280nm. There was no protein detectable by the method of Lowry, et al. and there was no DNA detectable with diphenylamine. The fraction did give a positive prcinol reaction consistent with the presence of RNA or pentose.
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Murray, A., Jansons, R. & Mosier, H. 317 PRESENCE IN RAT SERUM OF AN INHIBITOR OF 3H-THYMIDINE INCORPORATION BY CHONDROCYTES IN VITRO. Pediatr Res 12 (Suppl 4), 416 (1978). https://doi.org/10.1203/00006450-197804001-00322
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DOI: https://doi.org/10.1203/00006450-197804001-00322