The possible role of oral epithelial cells in tissue-type plasminogen activator-related fibrinolysis in human saliva.

We studied the fibrinolytic activities of the following subfractions of unstimulated human whole saliva on plasminogen-rich fibrin plates: (1) submandibular saliva, (2) parotid saliva, and (3) smears of buccal epithelial cells from ten healthy males. A cell-bound plasminogen activator could be demonstrated in the sediments of all three subfractions of whole saliva. The incorporation of antibodies (goat IgG) against human two-chain tissue-type plasminogen activator (t-PA) could quench the assessed fibrinolytic activities, whereas additional experiments suggested the absence of urokinase-like and F XII-dependent activators of fibrinolysis. The determinations in growth medium from buccal-epithelial cell culture of t-PA antigen by means of enzyme-linked immunosorbent assay showed the presence of t-PA. These clinical and experimental findings suggest that buccal-epithelial cells produce t-PA, while the activity of t-PA in parotid and submandibular saliva is very low.