THE MATRIX COMPONENTS OF THE EPIPHYSEAL GROWTH PLATE AND ARTICULAR CARTILAGES FROM DOGS TREATED WITH AMMONIUM TETRATHIOMOLYBDATE, A COPPER ANTAGONIST

Abstract

As part of a project to study the effect of copper deficiency (CD) on bone development in young dogs, the composition and metabolism of proteoglycans (PGs) and extractability of collagens in the epiphyseal growth plate cartilage (EGPC) and articular cartilages (AC) were investigated. Copper deficiency was induced by feeding ammonium tetra-thiomolybdate (TTM) a copper antagonist. The collagen of cartilages from TTM-treated animals was significantly more soluble in 0-5 M saline than control tissues. While no distinction between TTM-treated and control cartilages was evident in terms of PG content or extractability under associative (0-5 M-GuHCl) or dissociative (4-0 M-GuHCl) conditions, the sedimentation behaviour of the PG aggregates following CsCl density gradient ultracentrifugation suggested less polydispersity of PGs in preparations from the TTM-treated animals. Moreover, analysis of the PG monomers from EGPC of TTM animals showed galactosamine/glucosamine ratios higher than control preparations, suggesting a reduced keratan sulphate content in these preparations. Organ culture of EGPC showed a significant reduction in the incorporation of ³⁵S into PGs and of ³H-thymidine into DNA in the tissues of TTM-treated animals relative to controls. From these findings we deduce that the catabolism of PGs and the extent of collagen cross-linking in EGPC of TTM-treated animals may be reduced relative to age-matched control tissues.