Plasminogen in human saliva

Plasminogen has been demonstrated in human parotid submandibular and whole saliva both immunologically and functionally by activation with streptokinase. There was a significantly higher level of plasminogen in whole saliva than in either parotid or submandibular saliva, but these differences were largely eliminated after centrifugation. This was due to the tissue plasminogen content of leucocytes and epithelial cells which are present in whole saliva but which are removed by centrifugation. Plasminogen is therefore predominantly secreted in saliva. Since clinically fibrin clots seldom persist on the oral mucosa it is suggested that a potent plasminogen-assisted in vivo system of fibrinolysis may be operating in the oral mucosa.