Colloid and crystal formation in parotid saliva of cystic fibrosis patients and non-cystic fibrosis subjects. II. Electron microscopy and electrophoresis.

Centrifuged pellets of turbid parotid saliva from cystic fibrosis (CF) patients and non-CF subjects, obtained from saliva kept at 2 degrees for 10 min, had the electron microscope appearance of amorphous, round particles, and were thought to be colloidal aggregates of organic material. Drops of turbid saliva, from samples incubated for 2 hr at 2 degrees or 37 degrees, additionally contained discrete, electron-dense crystals having well defined angular morphology: usually cubic, retangular, or approximately hexagonal. The inhibitors, urea, guanidine hydrochloride, and EDTA, resulted in no crystals being observed. Selected area electron diffraction from individual crystals showed predominantly hexagonal, rectangular patterns could be indexed as coming from hydroxyapitite. A transition from the hexagonal to the rectangular pattern and back to the hexagonal pattern could be obtained from individual crystals tilted in the electron microscope. The square diffraction pattern may be from octa-calcium or brushite. Polyacrylamide gel disc electrophoresis of the parotid saliva indicated that the sparingly soluble proteins in the 2 degree and 37 degree pellets comprised proline-rich proteins and a calcium-precipitable, trichloroacetic acid (TCA)-precipitable phosphoprotein, which fluoresced with amido schwarz and Coomassie brilliant blue G250.