Some cation-binding properties of cartilage

Abstract

Decalcified bovine nasal septum showed equal binding capacities for Na+, K+, Mg2+, Ca2+, Sr2+ and Ba2+ ions. This capacity was closely correlated with the sulphate content, indicating that chondroitin sulphate was responsible for the major portion of the binding. Cu2+ and Be2+ ions were found to be bound to a greater extent, and NH4+ ions were bound to a less extent, than the ions mentioned above. It is possible that the greater binding of Cu2+ and Be2+ ions may be related to the powerful inhibition of calcification of rachite-bone sections (Sobel, 1955) exhibited by these ions in vitro. This greater binding is attributed to the binding by chondroitin sulphate of multinuclear ions of Cu2+ and Be2+ . The binding capacity for calcium was shown to vary considerably with pH, and the reasons for the variation were discussed. The possibility that the cartilage may act as a complexing agent in the binding of metals was studied by potentio-metric-titration methods. It was concluded that complex compounds are formed and the cations Be2+, Mg2+ and Cu2+ are bound sufficiently strongly to prevent the precipitation of the metal hydroxides (or basic salts).