Background: In this study, we used a new computerized analytical method for the measurement of the endothelial function in sequential ultrasound images and compared it with histological studies, using the abdominal aorta in normal and atherosclerotic rabbits.
Methods: Six rabbits received a standard rabbit chow as the normal group and the other 6 rabbits were fed a high cholesterol diet for four weeks as the atherosclerotic group. B-mode images of the abdominal aorta with 46 frames per second were saved over three cardiac cycles at baseline and during acetylcholine or nitroglycerin drug infusion in the normal and atherosclerotic rabbits. In order to evaluate endothelial-dependent relaxation, acetylcholine-mediated dilation (AMD) was measured during the infusion of acetylcholine at a rate of 0.5 μg/kg/min and endothelial-independent relaxation was evaluated by measuring nitroglycerine-mediated dilation (NMD) during the infusion of nitroglycerin at a rate of 5 μg/kg/min. In addition, the ultrasonic evaluation was confirmed by histopathological evaluation of the abdominal aorta.
Results: Significant differences in AMD were detected between the normal and the four-week cholesterol-fed rabbits (p value<0.05), whereas there were no significant differences in NMD between the two groups (p value>0.05). No microscopic intimal lesions were seen in the normal rabbits, but intimal thickening was observed in the histological studies in the four-week cholesterol-fed rabbits. Additionally, the total cholesterol, triglycerides, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol levels were remarkably increased in the sera of the four-week cholesterol-fed rabbits(p value<0.05).
Conclusion: A new automatic method can help accurately evaluate the endothelial function in normal and hypercholesterolemic rabbits.
Keywords: Atherosclerosis; Rabbits; Ultrasonography; Vasodilation.