Temporal variations of glandular kallikrein, protein and amylase in mixed human saliva.

Variations in the level of glandular kallikrein in human saliva may reflect physiological changes. Diurnal or circadian variations of many salivary components are important in relating changes in such components to oral or systemic conditions especially as most clinical studies are conducted between 0800 and 1700 h. Whole saliva was collected from 14 healthy young subjects at 0800, 1100, 1400 and 1700 h on two Fridays. Samples were centrifuged at 10,000 g for 10 min at 4 degrees C and the supernatant fractions stored at -20 degrees C. The enzymic activity of kallikrein was measured with D-valylleucylarginine-p-nitro-anilide as substrate. The activity of alpha-amylase and the total protein concentration (biuret) were also determined. Results were analysed in a repeated-measures design: there were no significant differences in kallikrein levels either within days or across days. There were significant differences for total protein and alpha-amylase levels within days but, in general, not across days. Minimal individual levels for protein and alpha-amylase were mostly at 0800 h; maxima were generally at 1400 or 1700 h. Kallikrein levels had no marked pattern of maximal or minimal distribution.