Hydroxyapatite in the pathogenesis of cystic fibrosis.

Submandibular saliva collected from cystic fibrosis patients and control subjects was separated by centrifugation into an insoluble deposit and a clear supernatant. The resulting calcium and phosphorus analyses performed on both fractions warranted a closer investigation as a consistent Ca/P molar ratio of 1.5 was found in the deposit of the cystic fibrosis patients, while no consistent ratio >1.0 was found in the deposit of the control subjects. The expected result, that calcium and phosphorus in the deposit of cystic fibrosis patients is present as the solid phase of hydroxyapatite, was confirmed by a detailed comparison of x-ray powder diffraction patterns of an ashed sample of this deposit and a similarly treated synthetic sample of hydroxyapatite.