Autoradiographic localization of beta-adrenergic receptors in rat oviduct

Catecholamines are known to have an inhibitory effect on oviductal smooth musculature by changing the adrenergic receptors activity. In order to further investigate the role of epinephrine and/or norepinephrine in oviduct, the distribution of beta-adrenergic receptors has been studied in the rat oviduct, using in vitro autoradiography and [125I]cyanopindolol (CYP), as radioligand. The specificity of the labelling and the characterization of receptor subtypes in different cell types was achieved by displacement of radioligand with increasing concentrations of zinterol, a beta-adrenergic agonist with preferential affinity for the beta 2-adrenoreceptor subtype and practolol, a beta-adrenergic antagonist that binds preferentially to beta 1-subtype. Quantitative estimation of ligand binding was achieved by densitometry. It was shown that the vast majority of beta-receptors were of the beta 2-subtype and were found in smooth muscle layers as well as in the epithelium. The latter localization suggests a role for epinephrine and/or norepinephrine on the oviductal epithelium.