SULPHATED ACID MUCOPOLYSACCHARIDE METABOLISM IN THE RABBIT INTERVERTEBRAL DISC

¹ Department of Orthopaedics, University of Washington School of Medicine, Seattle, Washington, United States of America; Edinburgh, Scotland
² Department of Orthopaedics, University of Washington School of Medicine, Seattle, Washington, United States of America; Sydney, Australia

1. The uptake of S³⁵ labelled sodium sulphate has been studied autoradiographically in the intervertebral disc of the young rabbit.

2. The sojourn of the isotope in the tissues includes an intracellular phase of approximately twenty-four hours, followed by an extracellular phase.

3. The cells exhibiting by far the greatest affinity for the sulphate ion are the peripheral groups of cells of the nucleus pulposus, while the chondrocyte-like cells of the cartilaginous segment of the annulus fibrosus are also fairly active. The central cells of the nucleus and the fibroblasts of the outer one-third of the annulus have a much lower uptake.

4. By analogy with similar studies on hyaline cartilage, and on the basis of correlation between the alcinophilia of the tissues and the concentration of the label, both before and after hyalase digestion of the tissue, it is considered that in the young rabbit disc, as in articular cartilage, the sulphate is incorporated primarily into chondroitin sulphate.

5. The elimination of the isotope from the nucleus at twenty-four days and the persistence of the label in the annulus fibrosus at thirty-two days tends to suggest that the metabolic turnover of acid mucopolysaccharide is considerably slower in the annulus than in the nucleus.