Correlation of lysozyme activity with proteoglycan biosynthesis in epiphyseal cartilage

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Abstract
Pig epiphyseal cartilage (proximal ulna epiphysis) previously incubated in vitro in the presence of sodium [35S]sulfate or [3H]thymidine was either analyzed by autoradiography or separated into 9 morphologically defined consecutive layers and investigated for35S-incorporation into the guanidinium chloride-extractable proteoglycans and for lysozyme activity. The lowest35S incorporation and lysozyme activity were determined in the zone of resting cells, but there is a consecutive increase in the rate of proteoglycan synthesis and lysozyme activity toward the diaphyseal cartilage-bone junction, with the maximum at the lower columnar cell zone and a sharp reduction of both parameters at the hypertrophic zone. The maxima of35S incorporation and [3H]thymidine incorporation do not coincide. The guanidinium chloride-soluble proteoglycans exhibit macromolecular polydispersity. Fractions excluded from as well as retarded by Sepharose 2B gel could be separated and were detected in all zones. The results indicate a correlation of proteoglycan biosynthesis and lysozyme activity in epiphyseal cartilage.