Electron microscopic autoradiography of 35SO4-labelled material closely associated with collagen fibrils in mammalian synovium and ear cartilage.

Electron microscopic autoradiography of connective tissue obtained from mice and rabbits previously injected with 35SO4 indicated that sulphated proteoglycans are localized on collagen fibrils. Ruthenium Red-positive transverse belts surrounding fibrils near the a-bands were heavily labelled, but fine lateral filaments of Ruthenium Red-positive material were not. These filaments, which interconnect collagen fibrils in a variety of connective tissues may represent linear aggregations of hyaluronic acid, glycoproteins and non-sulphated or long-lived sulphated proteoglycans.