Localization of α₁-adrenoceptor in the rat kidney: In vitro autoradiography using [³H]-bunazosin

We studied the precise localization of α₁-adrenoceptor in the rat kidney using in vitro macro- and micro-autoradiography (ARG) of [³H]-bunazosin. The slide-mounted nonfixed frozen sections (10 μm) of kidney were incubated with [³H]-bunazosin (5 nM) at 24°C for 45 min, and then applied to macro- and micro-ARG. The macro-ARG revealed that the bunazosin binding sites were present mainly in the rat renal cortex. These bindings were evaluated to be specific by means of computerized image analysis system (RAS 1,000) of ARG. Micro-autoradiogram showed that the tubules in the renal cortex had higher specific grain density than the glomeruli. These findings suggested that α₁-adrenoceptor in the rat kidney located mainly on the cortical tubules.