Quantitative localization of angiotensin II receptor subtypes in spontaneously hypertensive rats

Angiotensin II (Ang II) receptors were labelled by in vitro autoradiography using 125I-[Sar1,Ile8]Ang II as a ligand in the kidney, adrenal gland, thoracic aorta, and hindbrain of adult spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Ang II receptors were differentiated into subtypes by susceptibility to subtype 1 (AT1) and subtype 2 (AT2) antagonists. In both rat strains, the adrenal cortex contained predominantly AT1 receptors, while AT2 receptors predominated in the adrenal medulla. The kidney contained exclusively AT1 receptors in glomeruli, proximal tubules, and the outer medulla. AT1 receptors were predominant in the thoracic aorta. The nucleus of the solitary tract (NTS), dorsal motor nucleus of the vagus (DM10), area postrema, and spinal trigeminal nucleus (Sp5) contained exclusively AT1 receptors, whereas the nucleus of the inferior olive contained AT2 receptors predominantly. Significant differences in receptor density were observed between SHR and WKY. The adrenal cortex, renal outer medulla, NTS, DM10, and Sp5 displayed higher AT1 receptor density in SHR than in WKY. These results indicate that expression of AT1 receptors is regulated differently in important targets of Ang II in SHR, and suggest that altered regulation of AT1 receptor expression may be relevant to the pathogenesis of hypertension in SHR.