Metabolism of cartilage proteins in cultured tissue sections

The biosynthesis and turnover of cartilage proteins was studied in organ cultures of bovine tracheal-cartilage sections. In cultures labelled with [3H]leucine, more than 99% of the labelled macromolecules were retained in the sections. About half of the [3H]leucine-labelled protein was extracted with 4M-guanidinium chloride. The incorporation of [3H]leucine into protein extractable with guanidinium chloride was linear with time, after an initial delay of 20-25 min. The 148kDa and 36kDa cartilage proteins were major labelled components in this extract. The elimination of the proteins was studied by using a pulse-chase protocol. The 148kDa protein was found to have a very slow turnover, similar to that of proteoglycans, whereas the 36kDa protein was eliminated more rapidly.