Pressure-Induced Renal Injury in Angiotensin II Versus Norepinephrine-Induced Hypertensive Rats

The susceptibility to renal perfusion pressure (RPP)-induced renal injury was investigated in angiotensin II (Ang II)-versus norepinephrine (NE)-infused hypertensive rats. To determine the magnitude of RPP-induced injury, Sprague-Dawley rats fed a 4% salt diet were instrumented with a servocontrolled aortic balloon occluder positioned between the renal arteries to maintain RPP to the left kidney at baseline levels whereas the right kidney was exposed to elevated RPP during a 2-week infusion of Ang II IV (25 ng/kg per minute), NE IV (0.5, 1.0, and 2.0 mu g/kg per minute on days 1, 2, and 3 to 14, respectively), or saline IV (sham rats). Over the 14 days of Ang II infusion, RPP averaged 161.5 +/- 8.0 mm Hg to uncontrolled kidneys and 121.9 +/- 2.0 mm Hg to servocontrolled kidneys. In NE-infused rats, RPP averaged 156.3 +/- 3.0 mm Hg to uncontrolled kidneys and 116.9 +/- 2.0 mm Hg to servocontrolled kidneys. RPP averaged 111.1 +/- 1.0 mm Hg to kidneys of sham rats. Interlobular arterial injury and juxtamedullary glomerulosclerosis were largely RPP dependent in both models of hypertension. Superficial cortical glomerulosclerosis was greater and RPP dependent in NE-versus Ang II-infused rats, which was primarily independent of RPP. Outer medullary tubular necrosis and interstitial fibrosis were also primarily RPP dependent in both models of hypertension; however, the magnitude of injury was exacerbated in Ang II-infused rats. We conclude that elevated RPP is the dominant cause of renal injury in both NE- and Ang II-induced hypertensive rats and that underlying neurohumoral factors in these models of hypertension alter the pattern and magnitude of RPP-induced renal injury. (Hypertension. 2009; 54: 1269-1277.)