Peroxidase activity loss after filtration and centrifugation of whole saliva. Influence of citrate.

Filtration or centrifugation are two methods frequently used to clarify human whole saliva. This study compares both the drop in peroxidase activity following filtration (49.3% +/- 16.4%; N = 12) or centrifugation (33.6% +/- 15.9%; N = 6) and the drop in total protein concentration after filtration (33.9% +/- 13.4%) and centrifugation (23.6% +/- 8.7%). After filtration, the loss was not only due to retention of the large particle-bound fraction but also to adsorption on the filter membranes. This adsorption could be inhibited by a previous dilution of saliva in a citrate buffer, which also gave rise to active subunits with a molecular weight less than or equal to 100 kDa.