Pseudocholinesterase activity and its origin in human oral fluid.

Pseudocholinesterase (PCE) activity in oral fluid of 31 male and 24 female subjects was determined using butyrylthiocholine iodide as substrate. Males had approximately twice as much salivary PCE activity as did females [4.8 +/- 2.4 (S.D.) U/1 and 2.2 +/- 1.5 (S.D.) U/1, respectively]. The activity was not much affected by salivary flow rate, although in men it was a little higher in stimulated than in unstimulated saliva. Salivary PCE activity showed diurnal variation. Accordingly, activities were about three times greater at four a.m. than at four p.m. Parotid PCE activity correlated with that of whole saliva in both men and women. PCE activity in crevicular fluid (four subjects) was 120 +/- 48 (S.D.) U/1. An elevation of PCE activity in oral fluid was found after experimental induction of gingival inflammation. However, the mean PCE activity of patients with clinical gingivitis was not significantly higher than that of healthy subjects, although some exceptionally high values were found. Sonicated samples of plaque did not contain any PCE activity. No correlation existed between PCE activities in saliva and serum.