Immunocytochemical study of proteinase F in the mouse submandibular gland.

Esteroproteinases extracted from the submandibular gland (SMG) of normal male mice were fractionated by isoelectric focusing into three major peaks with isoelectric point (pI) values of 9.9 (P-esterase), 5.8 (proteinase A), and 5.6 (proteinase D). In castrated males or normal females, an additional esteroproteinase with a pI of 4.6 (proteinase F) appeared. By single radial immunodiffusion analysis using a specific anti-proteinase F serum, the proteinase F content in females or castrated males was found to be 15 times as high as that in normal males. These facts suggest that the synthesis of proteinase F is inhibited by androgens. Immunocytochemical localization of proteinase F in the SMG was examined by indirect enzyme-labeled antibody and ferritin-labeled antibody methods for light and electron microscopy, respectively. Castration of normal males caused morphological changes in granular convoluted tubular (GCT) cells, i.e., GCT cells with both several small secretory granules in their apical region and some striations at their basal region (light cells) were observed in addition to typical GCT cells. Immunoreactive proteinase F was exclusively localized in such small secretory granules of the light cells, but was only minimally present in large secretory granules of the typical GCT cells. In females, however, uniform localization of proteinase F among secretory granules of all GCT cells was observed. It is suggested that the small secretory granules in light cells are formed after castration.