Levels of pre‐kallikrein in resting and stimulated human parotid and submandibular saliva

Salivary tissue kallikrein is stored in an active form in human salivary glands. Pre-kallikrein has been demonstrated in mixed saliva, but it is not clear if the various salivary glands contribute equally. This study set out to determine if pre-kallikrein is present in human parotid and submandibular salivas at rest, whether levels change during stimulation, and to compare the pattern of pre-kallikrein and kallikrein secretion with that of total protein. Resting and citric acid-stimulated parotid and submandibular, and gum-stimulated parotid saliva samples were collected from 6 healthy subjects. Salivary flows were determined gravimetrically. Total protein concentration and kallikrein enzymic activity were assayed using standard techniques. Pre-kallikrein was assayed following trypsinisation of duplicate samples. Pre-kallikrein was present in parotid and submandibular ductal saliva. Proportions of pre-kallikrein and active kallikrein were similar in salivas secreted at rest and during stimulation, and both outputs mirrored protein output in both major glands. Gum-stimulated parotid saliva showed lower activity than resting, and no differences were seen between resting and stimulated submandibular samples.