Colloid and Crystal Formation in Parotid Saliva of Cystic Fibrosis Patients and Non-Cystic Fibrosis Subjects. I. Physicochemistry

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Abstract
Extract: Two types of turbidity were found in parotid saliva from both cystic fibrosis (CF) patients and non-CF subjects. On cooling saliva, a rapidly forming, reversible, cold-dependent turbidity appeared in increasing amounts with decreasing temperature and increasing protein concentration. At 37°, a slowly forming, stable turbidity appeared in increased amounts in parotid saliva samples containing increased amounts of calcium. The 2° centrifuged pellet consisted predominantly of protein, whereas the 37° pellet contained calcium, inorganic phosphate, and protein. The cold-dependent turbidity at 2° was not inhibited by EDTA, but 37° turbidity was dramatically inhibited. Urea and guanidine hydrochloride reduced 2° turbidity, and, to a lesser extent, inhibited 37° turbidity. The tendency towards higher levels of protein, amylase, and calcium in CF compared with child control parotid saliva (4, 6) causes a greater incidence and degree of turbidity formation in saliva of CF patients. In this paper only the nature of the turbidity has been investigated, not its relative occurrence in each group of subjects. Speculation: In cystic fibrosis, a tendency towards high levels of calcium and protein in parotid saliva would mediate towards deposition of colloidal protein and calcium phosphate within parotid gland ducts and on tooth surfaces adjacent to duct orifices. A similar overse-cretion of calcium and protein in other CF exocrine secretions may result in obstruction by stagnant or cooled secretions.