Leucocyte metabolism in human saliva

Abstract

This report advances a new perspective concerning the metabolism of whole saliva and its significance as a biological fluid in man in health and disease. Cold paraffin stimulated whole saliva was fractionated by differential centrifugation. The separation of mammalian cells was confirmed by direct microscopic count of epithelial cells and identifiable leucocytes. The separation of bacteria was confirmed by direct microscopic counts of large rods and total aerobic bacteria plate counts. O 2 uptake (Q O 2 ), total aerobic acid production (Q A Air) and total anaerobic acid production (Q A N 2 ) in the presence of D-glucose were determined for whole saliva and the following fractions prepared from the same whole saliva: (1) 50 × g sediment (mammalian cell and granular mass fraction), (2) 50 × g supernatant (bacteria and mammalian subcellular particle fraction) and (3) 27,000 × g supernatant (cell free and subcellular particle free fraction). Ninety to one hundred per cent of the whole saliva activities were recovered in the unwashed mammalian cell and granular mass fractions in the presence of the 27,000 × g supernatant fractions. When the mammalian cell and granular mass fraction was washed and resuspended in the 27,000 × g supernatant, 76–88 per cent of the whole saliva activities were recovered. The residual activities were found in the wash supernatant. The bacteria and mammalian subcellular particle fractions exhibited 16–34 per cent of the activities found in the whole saliva. The requirement by the saliva sediments for the 27,000 × g supernatant to re-establish the intact metabolizing system is one measure of the mammalian cell homogenate-like activities of paraffin stimulated whole saliva. Six other characteristics of the homogenate-like nature of paraffin stimulated whole human saliva are given. It is concluded that aerobic and anaerobic salivary metabolism is associated primarily with its contained oral leucocyte protoplasm. The contribution the oral micro organisms make to the whole saliva's total metabolism is of a previously unrecognized low order of magnitude.