Immunocytochemical study of prorenin procrssing in the mouse submandibular gland, using antibodies against prorenin and its cleaved fragments.

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According to the complete amino acid sequence of the mouse submandibular gland renin precursor (Ren-2-prorenin) (Panthier et al.,1982; Misono et al.,1982), the short peptides, which stride the positions of proteic cleavages, each occuring after three basic residues : Cys 18-Thr 19, Mg 63-Der 64, and Mg 363-Asp 364, respectively, were designed, chemically synthesized, and immunized rabbits. The preparation of specific antibody against the second peptide, ST-161: Thr-Lys-Arg-Ser-Ser-Leu-Thr-Asp-Leu-Ile-Cys, which strides between the Lys62-Arg63 was succeeded. This antibody seemes to recognize prorenin, but not mature renin. Western blotting analysis, however, was not performed to examin the specificity of the antibody. It was unluckly that other peptides designed by the author were not reacted as the antigen, so, the antibodies were not obtained.The immunocytochemical localization and distribution of the ST-161 was examined in the mouse submandibular gland by indirect Cy3 (indocarbocyanine)-labeled antibody method for light microscopy. Red immunoreactive materrials were localized at the pen-nuclear region of the granular convoluted tubule cells, but not on the secretory granules. These immunostain-ed region was corresponding to the trans-Golgi network, containing Golgi apparatus and immature secretory granules. It is therefore concluded that the corresponding portion of mouse Ren-2-prorenin may be cleaved off in the Golgi apparatus or immumature secretory granules. It has not been successful to date to confirm this idea by immunoelectron microscopy.