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

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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.