Statistical evidence for the relation between citrate and carbonate in human cortical bone.

Bone specimens from the anterior iliac crest were collected post-mortem from 128 subjects whose death had been primarily caused by acute coronary disease or accidents. The cortical bone was separated and used for the following determinations: citrate by an enzymatic method, carbon dioxide by microdiffusion, chloride and phosphorus by spectrophotometry, fluoride by the ion-selective electrode technique, and Ca, Mg, Zn by atomic absorption spectrophotometry. The citrate concentration (+/- SD) was 10.9 +/- 3.1 mg/g (dry weight) and was not age-dependent. A statistically significant negative correlation was obtained between citrate and carbon dioxide, however, which was confirmed by regression analysis. The only statistically significant differences in carbon dioxide and fluoride concentrations between three citrate groups were obtained between the lowest group (3.2-8.7 mg/g) and the highest (13.1-16.8 mg/g). In conclusion an inverse relationship may suggest either an effect of citrate on the binding of carbonate to apatite structures, or that the carbonate concentration is dependent to a slight degree on citrate metabolism.