beta-Adrenergic receptors in rat kidney: direct localization by a fluorescent beta-blocker

A new fluorescent beta-adrenergic blocker, 9-amino-acridin propranolol (9-AAP), was administered intravenously to albino rats. Fluorescent aggregates of 9-AAP binding sites were concentrated in the vascular poles of the glomeruli in association with the preglomerular afferent arterioles. 9-AAP fluorescence was reduced following pretreatment with (+/-)- and (-)-propranolol and was less affected in rats pretreated by the (+)-racemic isomer. 9-AAP binding sites were also observed on the lining epithelium of the renal collecting system. Our data suggest that 9-AAP may label beta-adrenergic receptors in rat kidney.