Early endothelial dysfunction in cholesterol-fed rabbits: a non-invasive in vivo ultrasound study.

We evaluated a non-invasive ultrasound technique to assess early endothelial function in rabbits and compare data with ex vivo measurements.Twenty-four rabbits (fed with a cholesterol diet (0.5%) for 2 to 8 weeks) were given progressive infusions of acetylcholine (0.05–0.5 μg/kg/min) and their endothelial function was assessed in vivo by transcutaneous vascular ultrasound of the abdominal aorta. Ex vivo endothelial function was evaluated on isolated aortic rings and compared to in vivo data.Significant endothelial dysfunction was demonstrated in hypercholesterolemic animals as early as 2 weeks after beginning the cholesterol diet (aortic cross-sectional area variation: -2.9% vs. +4% for controls, p < 0.05). Unexpectedly, response to acetylcholine at 8 weeks was more variable. Endothelial function improved in 5 rabbits while 2 rabbits regained a normal endothelial function. These data corroborated well with ex vivo results.Endothelial function can be evaluated non-invasively in vivo by transcutaneous vascular ultrasound of the abdominal aorta in the rabbit and results correlate well with ex vivo data.Endothelial dysfunction occurs early in the development of atherosclerosis. Historically, evaluation of endothelial function in small animals has been performed on isolated vessel segments, or vessels exposed by surgical procedures. Very few attempts were made to develop a method of analysis of endothelium-dependent relaxation in vivo[1-5]. In those studies, an invasive intravascular ultrasound approach was used. Correlation between results obtained in vivo and data on isolated arteries ex vivo was never assessed.Non-invasive methods to study endothelial function in humans (e.g. ultrasound of the brachial artery) have been used for many years and have yielded an important amount of data [6-12]. Unfortunately this non-invasive technique has never been transposed to animal studies.The objective of the current study was to assess the reliability of transcutaneous vascular u