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Angiotensin II (Ang II) exerts a variety of actions through specific receptor binding in the kidney. These include modulation of renal hemodynamics, glomerular filtration rate (GFR), and tubular reabsorption. Quantitative in vitro autoradiography was used to localize the Ang II receptors and angiotensin converting enzyme (ACE) in rat, rabbit, and human kidney. We incubated 20 μm cryostat sections of kidney with either ¹²⁵I-[Sar¹]Ang II or ¹²⁵I-[Sar¹,Ile⁸]Ang II for Ang II binding or with ¹²⁵I-351A for ACE localization. The resulting autoradiographs were analyzed by computerized densitometry. A high density of Ang II binding was found over glomeruli and vasa recta bundles in all species examined. The interbundle area of the outer medulla was associated with low to moderate binding of Ang II. Moderate binding of Ang II was observed over proximal convoluted tubules in the outer cortex of rat kidney. ACE was …