A comparison of proteoglycan from chick cartilage of different types and a study of the effect of vitamin D on proteoglycan structure.

Normal chick growth cartilage contains mainly large proteoglycans that interact well with hyaluronic acid. In contrast normal articular and sternal cartilages contain mainly smaller molecules that interact poorly with hyaluronic acid. Similar smaller proteoglycans are present in all the cartilages in the rachitic state. The smaller proteoglycans all appear to be synthesized as such, and not to arise from degradation of larger molecules unless such degradation occurs extremely rapidly after synthesis. Supplementation of the vitamin D-deplete animals with calcium resulted in the production of large proteoglycans by the growth cartilage, but did not affect the size of the proteoglycan produced by the articular or sternal cartilages. It would appear that in these chicks the chondrocytes of the growth cartilage may be unique in their ability to produce large aggregating proteoglycans, and in their response to plasma calcium levels.