Studies on kallikrein in the duct systems of the salivary glands of the cat.

By correlating immunofluorescence light microscopy with electron microscope studies and with kallikrein concentrations under various conditions, we have made the following observations and conclusions about kallikrein in the submandibular and other salivary glands.1. In the submandibular gland, specific immunofluorescence to kallikrein was observed in the luminal region of the striated ducts particularly, but also in the outer epithelial cells of the stratified epithelial collecting ducts. Sympathetic nerve stimulation resulted in a reduction in intensity of specific fluorescence and in its increased localization towards the lumen. The nearly complete elimination of kallikrein from the gland by duct obstruction for four days resulted in complete disappearance of specific fluorescence in the gland. Prolonged parasympathetic nerve stimulation at frequencies which did not reduce the kallikrein concentration of the gland failed to alter the specific immunofluorescence despite copious secretion of saliva. Our results failed to reveal evidence of secretion of kallikrein either into or towards the interstitium of the gland. The luminal layer of stratified epithelial cells in the collecting ducts contained small secretory granules closely resembling those in the striated ducts. Our results are not conclusive, but do suggest that kallikrein is located in these granules whence it is secreted into the lumen of the duct.2. The parotid gland was found to contain much lower concentrations of kallikrein than the submandibular gland. This finding was associated with the presence of far fewer striated ducts in the parotid gland. Otherwise, specific fluorescence and the response to sympathetic nerve stimulation was like that of the submandibular gland. Small secretory granules in the striated and collecting ducts resembled those of the submandibular gland.3. The sublingual gland, like the parotid, had a low concentration of kallikrein and very few striated ducts. These ducts were unevenly distributed and were concentrated in only a few lobules of the gland. Specific immunofluorescence was seen only in sections containing striated ducts.4. The possible physiological role of kallikrein in the salivary glands is discussed.