Autoradiographic localization of β‐adrenoceptor subtypes in guinea‐pig kidney

Abstract

1 The distribution of β-adrenoceptor subtypes in slide-mounted sections of guinea-pig kidney has been examined by the technique of in vitro labelling combined with autoradiography. 2 Binding of (-)-[¹²⁵I]-cyanopindolol (Cyp) to kidney sections equilibrated and dissociated slowly, was saturable and stereoselective with respect to the isomers of propranolol and pindolol. These characteristics were appropriate for binding to β-adrenoceptors. 3 Delineation of β-adrenoceptor subtypes was achieved by use of betaxolol (β₁-adrenoceptors) and ICI 118,551 (β₂-adrenoceptors) and computer assisted curve fitting techniques. Both β₁- and β₂-adrenoceptors were present in the proportions 1:2. 4 ³H-Ultrofilm images of (-)-[¹²⁵I]-Cyp binding to guinea-pig kidney sections showed localized patches of binding in the cortex and concentrated binding in the outer stripe of the medulla. Cortical receptors were of the β₁ subtype and those associated with the outer stripe of the medulla were of the β₂-adrenoceptor subtype. β₁-Adrenoceptors were concentrated over glomeruli and β₂-adrenoceptors over the straight portion of the proximal tubule.