Human mixed saliva protein concentration.

Abstract

The concentration of protein in human mixed saliva normally is about 100 to 300 mg%, and these values are not modified significantly by stimulation (H. E. SCHUJLTZE and J. F. HEREMANS, Molecular Biology of Human Proteins, vol I, 1966, pp 762-772). Because of inherent contamination of mixed saliva by bacteria and food debris normally present in the oral cavity, it is advantageous to study isolated secretions from individual salivary glands. Because of the rapid formation of mucin clot, which tends to render most of the existing chromatographic procedures useless, mixed saliva is difficult to fractionate; consequently, most of our knowledge of its isolated protein components has been derived from selectively collected parotid or submandibular fluids. While attempting to find physiologic correlations between the oral cavity and systemic disease, however, we have thought it more appropriate to use (in spite of its drawbacks) the mixed salivary fluid. This study reports the protein concentration in mixed saliva of a normal male studied over a period of two years and is part of an investigation of the isolation, characterization, and physiologic significance of proteins in human mixed saliva. Saliva was collected without stimulation once every two weeks (beginning October 1968) by expectoration into a graduated cooled vessel (4 C) that contained thymol crystals to inhibit bacterial growth. To avoid excessive variation caused by diurnal fluctuations, samples were obtained in the evening (8:30 to 10:00 PM), two hours after the evening meal, after normal dental hygiene. Before sample collection the oral cavity was rinsed thoroughly with distilled water. Immediately after collection samples were cleared by centrifugation at 27,000 X g for 30 minutes in a refrigerated centrifuge* and the supernatant was analyzed for protein with a spectrophotometer. t In some instances, for comparative purposes, the cleared saliva was dialyzed against deionized, glass-distilled water at 4 C for 18 hours before protein determination. No attempt was made to measure the flow rate, but in general the volume of saliva collected was kept fairly constant: mean, 125.5 ml; range, 60 to 210 ml. Forty-five samples (of which 12 were di-