Autoradiographic localization and characterization of binding sites for atrial natriuretic peptide in the rat oral mucosa

Atrial natriuretic peptide (ANP) has been shown to have cellular growth-related effect as well as body fluid regulatory function. The epithelial layer of the oral cavity is vulnerable to these stimuli and has relatively short turn-over rate. The purpose of the present study was to find the presence of ANP receptors using in vitro microautoradiography and quantitative autoradiography in the rat oral mucosa. The specific binding sites for 125 I-labeled rANP (1-28) were concentrated mainly to the basal and parabasal layers of the epithelia of the tongue body and the hard palate. 125 I-labeled rANP (1-28) binding was not displaced by human angiotensin II and ADH. In the tongue and the hard palate, dissociation constants were 3.34 ±0.7 1.35 and 4.09 ±0.7 1.52 nM, respectively. The present study demonstrates, for the first time, the location and the characteristics of the ANP binding sites in the oral mucosa. These findings suggest that the AN! system may be involved in the physiological function of the oral mucosa.