Angiotensin II Infused Intrarenally Causes Preglomerular Vascular Changes and Hypertension

The effects on the renal vasculature and on arterial blood pressure of chronic 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 artery (contralateral nephrectomy). Intrarenal Ang II infusion for 25 days produced 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). Renal vessel lumen characteristics were assessed with an established, maximally dilated, isosmotic perfused kidney preparation. This revealed a small dose-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 of the pressure-glomerular filtration rate relation (P=0.04 and 0.03, respectively). The effects of Ang II infusion on arterial pressure were not affected by the timing of the contralateral nephrectomy but were reduced when the contralateral kidney remained in situ. Acute losartan administration (10 mg/kg IV bolus) produced similar effects on arterial pressure in rats infused 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 II (0.5, 1.5, or 4.5 ng. kg(-1). min(-1) for 25 days) had no effect on arterial pressure. Thus, chronic intrarenal infusion of low doses of Ang II resulted in changes in the renal vasculature compatible with dose-related structural reductions in the lumen diameter of preglomerular vessels and produced dose-related increases in arterial pressure.