Immunohistochemical localization of C-type natriuretic peptide in the rat submaxillary salivary gland

To define the localization and characteristics of C-type natriuretic peptide (CNP) in the rat submaxillary gland, immunohistochemistry and gel permeation–high-performance liquid chromatography were used. Immunoreactive (IR)-CNP was localized in cells of the granular convoluted tubule, striated duct and endothelial cells of the capillary, where atrial natriuretic peptide (ANP) was colocalized in consecutive sections, but not in acini. Gland extracts co-eluted with synthetic CNP and its content was 60.3±4.9 pg/mg protein (n=4). Molecular profiles of immunoreactive material showed two peaks corresponding to synthetic CNP(1–53) and CNP(1–22). These results indicate that CNP is colocalized with ANP in the duct and endothelial cells of the rat submaxillary gland. Therefore, CNP may have a physiological role in the submaxillary gland by interacting with ANP and/or other biologically active substances in the ducts and granular convoluted tubule cells.