Autoradiographic localization of binding sites for atrial natriuretic peptide and angiotensin II in the orofacial region of the neonatal rat

Atrial natriuretic peptide (ANP) and angiotensin II (Ang II) have been shown to have cellular growth-related effect as well as their classical function. In this study we aimed to localize ANP and Ang II receptors using in vitro autoradiography in the orofacial region of the neonatal rat. Also, we characterized receptor subtype by competition with des[Gln¹⁸ ,Ser¹⁹,Gly²⁰,Leu²¹, Gly²²] ANP(_4-23)(C-ANP) as a selective ligand for the clearance receptors to specific ¹²⁵I-rANP(1-28) bindings and with DuP753 and PD123319 as nonpeptide antagonists for AT₁ and AT₂ subtypes, respectively, to ¹²⁵I-Ang II bindings. The specific binding sites for ¹²⁵I-labeled rANP(1-28) were concentrated mainly in the dermis of the facial skin, the oral mucosa, and some portions of the developing maxillae and mandible. The specific ¹²⁵I-Ang II bindings were localized in the orofacial tissues. Incubation of consecutive sections with the selective AT₁ and AT₂ antagonists revealed that bindings were highly sensitive to the selective AT₂ competitor PD123319, and not to the selective AT₁ antagonist DuP753. Therefore, Ang II receptors in the orofacial region of the neonatal rat were mainly AT₂ subtype. These findings suggest that ANP and Ang II may have a role for the physiological function via specific receptors in the orofacial region of the neonatal rat.