Angiotensin II infused intrarenally causes preglomerular vascular changes and hypertension

The effects on the renal vasculature and on arterial blood pressure of chro nic infusion of low doses of angiotensin II (Ang II) into the renal artery were studied. Sprague Dawley rats were infused continuously with Ang II (0. 5, 1.5, or 4.5 ng . kg(-1) . min(-1)) or vehicle into the right renal arter y (contralateral nephrectomy). Intrarenal Ang II infusion for 25 days produ ced dose-dependent rises (P<0.001) in awake mean arterial pressure (111+/-1 , 119+/-5, and 130+/-3 mm Hg in rats receiving 0.5, 1.5, and 4.5 ng . kg(-1 ) . min(-1) Ang II, respectively) compared with 105+/-1 mm Hg (vehicle). Re nal vessel lumen characteristics were assessed with an established, maximal ly dilated, isosmotic perfused kidney preparation. This revealed a small do se-dependent right shift in the pressure-flow relation (P=0.05), as well as a dose-dependent right shift and a dose-dependent reduction in the slope o f the pressure-glomerular filtration rate relation (P=0.04 and 0.03, respec tively). The effects of Ang II infusion on arterial pressure were not affec ted by the timing of the contralateral nephrectomy but were reduced when th e contralateral kidney remained in situ. Acute losartan administration (10 mg/kg IV bolus) produced similar effects on arterial pressure in rats infus ed with vehicle or Ang II (4.5 ng . kg(-1) . min(-1)) for 14 days, P=0.89), indicating the lack of systemic spillover of Ang II. Intraperitoneal Ang I I (0.5, 1.5, or 4.5 ng . kg(-1) . min(-1) for 25 days) had no effect on art erial pressure. Thus, chronic intrarenal infusion of low doses of Ang II re sulted in changes in the renal vasculature compatible with dose-related str uctural reductions in the lumen diameter of preglomerular vessels and produ ced dose-related increases in arterial pressure.