Affinity of cartilage matrix for calcium

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Abstract
Cartilage matrix from rachitic rats mineralizes in vitro on incubation in appropriate solutions and, if the phosphorus concentration is constant, the degree of mineralization varies directly witd concentrations of calcium between 3.5 and 6.0 mg/100 ml. On adding to a standard incubating solution various organic or amino acids known to form chelates with calcium it was found that inhibition of matrix mineralization varied directly with the chelating propensity of these acids. These observations indicate that mineralizable cartilage matrix does not have an affinity for calcium exceeding that of any chelating agent tested. Moreover, as cartilage apparently requires calcium in a readily available, persumably ionic, form for mineralization, this tissue may be used as a means of determining the dissociation constants for calcium chelates. From the preliminary data obtained in this experiment dissociation constants were calculated for the following ligands: citrate, tartrate, malonate, succinate and glutamate. These derived values may be more appropriate to biological systems under simulated physiological conditions than are those determined by strictly chemical means.