THE MECHANISM OF FLUORIDE-INDUCED HYPOCALCEMIA

1 Fluoride intoxication leads to sudden cardiac death which has been a ssumed to result from the accompanying severe hypocalcaemia. The aim o f this study has been to investigate the suggestion that fluorapatite formation rather than CaF2 precipitation is responsible for this low c alcium. 2 Measurements of free Ca2+ and F- ion concentrations in HEPES buffered solutions containing F-, Ca2-, and phosphate ions at differe nt concentrations in the absence and presence of hydroxyapatite showed that the presence of hydroxyapatite enhanced the decrease of Ca2+ and F- concentration. 3 The ratio of Ca2+:F- clearance was 5:1 which is c onsistent with formation of fluorapatite. These results support the hy pothesis that hydroxyapatite acts as a nucleation catalyst for fluorop atite formation and this process is responsible for the hypocalcaemia induced by fluoride intoxication. 4 The proposed mechanism explains al so the metabolic acidosis which is frequently seen in cases of fluorid e intoxication,