Natriuretic peptide system in the rat lacrimal gland

The presence and characteristics of the natriuretic peptides and their receptors in the rat exorbital lacrimal gland were investigated. Serial dilution curves of the gland extracts were parallel to the standard curves of synthetic atrial natriuretic peptide (ANP) or C-type natriuretic peptide (CNP). Immunoreactive ANP or CNP in the gland extracts co-eluted with authentic ANP or CNP, and their contents were 4·95 ± 0·60 and 2·87 ± 0·53 pg mg^-1 protein (quadruplicate), respectively. By immunohistochemistry, strong immunoreactivities of ANP and CNP were co-localized in the tubules and excretory ducts of the gland, and moderate immunoreactivities were found in the myoepithelial cells and acini. Productions of guanosine 3'.5'-cyclic monophosphate by particulate guanylyl cyclase in the gland membranes were stimulated by natriuretic peptides in a dose-dependent manner, and that by CNP was larger than by ANP. Messenger RNAs for ANP, CNP and their receptors were detected by reverse transcription-polymerase chain reaction. These results indicate that natriuretic peptides and their specific receptors are found in the rat lacrimal gland. Therefore, it is suggested that natriuretic peptide system may play physiological roles in the rat lacrimal gland. (C) 2000 Academic Press.