Distribution and location of immunoreactive atrial natriuretic peptides inmiddle ear mucosa of guinea pig

The distribution and location of atrial natriuretic peptides (ANP) in the m iddle ear mucosa (MEM) of guinea pigs were studied with immunocytochemistry (avidin-biotin-peroxidase complex method) and immune-electron microscopy. A great quantity of ANP-immunoreactive (ANP-IR) cells, including oval small cells and irregular large cells, was observed in the tissue of the MEM. Th e strong ANP-IR product was observed in the inner membrane of the partial c apillary walls. Under immuno-electron microscopy, the ANP-IR product was fo und to be spheres of 250 to 350 nm in diameter The results of this study su ggest that the MEM has the function of secreting ANP. This paper provides t he morphological basis for the study of ANP's function in the MEM.