Characterization and localization of beta-adrenergic receptors in control and cryptorchidized rat testis by in vitro autoradiography.

beta-adrenergic receptors were localized and characterized in control and cryptorchidized rats to investigate further their role in testicular function. Slide-mounted cryostat sections were incubated with [125I]cyanopindolol, a specific ligand for beta-adrenergic receptors. The subtypes were characterized by the displacement of [125I]cyanopindolol binding by practolol, which binds preferentially to the beta 1 subtype, and zinterol, which is preferential for beta 2 receptors. Labeling was detected by autoradiography, first by exposing sections to Ultrofilm (LKB) and second by dipping slides in NTB-2 Kodak photographic emulsion. The histologic distribution of receptors was analyzed by counting silver grains overlying the testicular structures. It was found that the vast majority of receptors were of the beta 2-subtype. In intact rats, the greatest density of receptors was found in interstitial cells, with some specific labeling over the seminiferous tubules. However, in cryptorchidized animals, the proportion of beta 2 receptors in tubules that contained mainly Sertoli cells appeared to be markedly increased. The results obtained suggest that catecholamines have multiple sites of action in the testis.