Intrarenal AT1 receptor and ACE binding in ANG II-induced hypertensive rats

The intrarenal expression of angiotensin II (ANG II) type 1 (AT(1)) receptors and angiotensin-converting enzyme (ACE) was determined in ANG II-induced hypertensive rats (80 ng/min; 2 wk). Systolic blood pressure averaged 184 +/-3 and 125 +/-1 mmHg in ANG II-infused compared with Sham rats on day 12. Total kidney AT1 receptor protein levels were not altered significantly. AT1 receptor binding mapped by quantitative in vitro autoradiography was significantly decreased in glomeruli (172 +/- 25 vs. 275 +/- 34 disintegrations.min(-1).mm(-2)) and the inner stripe of the outer medulla (121 +/- 17 vs. 178 +/- 19 disintegrations.min(-1).mm(-2)), but not proximal convoluted tubules (48 +/-9 vs. 58 +/-6 disintegrations.min(-1).mm(-2)) of ANG II-infused compared with Sham rats. Proximal tubule ACE binding was significantly augmented (132 +/-4 vs. 97 +/-3 disintegrations.min(-1).mm(-2)) in ANG II-infused rats. In summary, during ANG II-induced hypertension, glomeruli and inner stripe of the outer medulla have reduced AT1 receptor binding. Proximal convoluted tubules exhibit maintained AT1 receptor density and increased ACE binding, which together with the elevated ANG II levels suggest that ANG II exerts a sustained influence on tubular reabsorption and consequently contributes to the development and maintenance of ANG II-dependent hypertension.