Effects of Norepinephrine on Renal Cortical and Medullary Blood Flow in Atherosclerotic Rabbits

Objective: The aim of this study was to explore the effect of norepinephrine (NE) on renal cortical and medullary blood flow in atherosclerotic rabbits without renal artery stenosis. Methods: Atherosclerosis was induced in 21 New Zealand white rabbits by feeding them a cholesterol-rich diet for 16 weeks. Thirteen healthy New Zealand white rabbits were randomly selected as controls. After atherosclerosis induction, standard ultrasonography was performed to confirm that there was no plaque or accelerated flow at the origin of the renal artery. Contrast-enhanced ultrasound (CEUS) was performed at baseline and during intravenous injection of NE. The degree of contrast enhancement of renal cortex and medulla after the injection of contrast agents was quantified by calculating the enhanced intensity. Results: The serum nitric oxide (NO) level in atherosclerotic rabbits was higher than that in healthy rabbits (299.6 +/- 152 vs. 136.5 +/- 49.5, P< 0.001). The infusion of NE induced a significant increase in the systolic blood pressure (112 +/- 14 mmHg vs. 84 +/- 9 mmHg, P=0.016) and a significant decrease in the enhanced intensity in renal cortex (17.78 +/- 2.07 dB vs. 21.19 +/- 2.03 dB, P<0.001) and renal medulla (14.87 +/- 1.82 dB vs. 17.14 +/- 1.89 dB, P<0.001) during CEUS. However, the enhanced intensity in the cortex and medulla of healthy rabbits after NE infusion showed no significant difference from that at baseline. Conclusion: NE may reduce renal cortical and medullary blood flow in atherosclerotic rabbits without renal artery stenosis, partly by reducing the serum NO level.