β Adrenergic receptors in rat kidney. Direct localization by a fluorescent β blocker

A new fluorescent β-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. The data suggest that 9-AAP may label β-adrenergic receptors in rat kidney.