Citrate in Mineralized Tissues

DENTINE contains about 0.9 per cent of citrate (FREE, 1943 ; ZIPKIN and PIEZ, 1950; STACK, 1951), of which some 5 per cent can be removed by extracting powdered dentine with distilled water at room temperature, and a further 10 per cent by extraction with boiling water. These observations suggest that the citrate does not exist solely as the free calcium salt, the solubility of which, though low, should be high enough to permit its total extraction with water. Little is known of the function of citrate in mineralized tissues, and the object of this preliminary investigation was to seek information concerning the nature of the citrate in dentine. Some evidence has been obtained which suggests that the citrate is associated with a peptide.