Supra- and infrarenal endothelial vascular reactivity on the rodent

Object: Human infrarenal aorta is prone to develop atherosclerotic lesions. Infrarenal aortic blood flow depends on lower limb muscular activity. Blood flow variations cause shear stress variations known to influence endothelial reactivity. The purpose of this study is to compare vascular reactivity of the suprarenal and infrarenal aorta. Material and methods: Endothelium-dependent relaxation to acetylcholine (ACH) and calcium ionophore (Cal), and endothelium-independent relaxation to sodium nitroprussiate (SNP) in 3 aortic segments (thoracic, abdominal suprarenal and infrarenal) harvested from Sprague-Dawley rats (n = 12) were studied in organ chambers. Results. Endothelium-dependent relaxations to ACH were similar for the 3 aortic segments. However, infrarenal aorta endothelial response to Cal was decreased compared to other segments whereas response to SNP was enhanced. Contractility to vasoconstrictor agonist (phenylephrine and KCl) was diminished compared to the suprarenal segments. Conclusion : Endothelial reactivity is not homogeneous throughout the rat aorta. Endothelial reactivity to Cal seems decreased in the infrarenal aorta which suggests a diminished nitric oxide synthase activity. The increased sensitivity of the infrarenal aorta to nitric oxide donor such as SNP suggests a compensatory mechanism.