Cardiology Department, University of Patras, Greece.
Exp Biol Med (Maywood). 2010 Mar;235(3):311-6. doi: 10.1258/ebm.2009.009319.
Dynamic mechanical disturbances in the aortic wall may lead to progressive aortic dilation and possibly aneurysmal formation. Here, we investigated the previously unexplored effects of aldosterone inhibition on aortic wall viscoelastic properties in hyperlipidemic rabbits. Thirty-six New Zealand male rabbits, fed a standard diet for four weeks, were separated into three groups: control (C; n = 10), standard diet; eplerenone (A; n = 12), hyperlipidemic diet plus 100 mg/kg/d eplerenone (last 4 weeks); and vehicle (V; n = 14), hyperlipidemic diet (no eplerenone). After eight weeks, animals were sacrificed and rectangular strips from the aortic wall, cut in radial and axial orientations, were prepared. Fresh, saline-wetted strips at 37 degrees C were subjected to cyclic sinusoidal elongation from zero to 20% of the resting length at a frequency of 1 Hz. The dynamic biomechanical viscoelastic characteristics, 'elastin phase' low modulus (E(L)), 'collagen phase' high modulus (E(H)) and dissipated-energy index, were determined. Aortic tissue preparations were also examined histologically. Eplerenone increased aldosterone concentrations but did not affect blood pressure, cholesterol or potassium concentrations. There was a significant reduction of E(H) (from 3.40 to 1.80 MPa; P < 0.01) and E(L) (from 0.46 to 0.27 MPa; P < 0.05) in group A in the radial direction compared with group C. In the axial direction E(L) significantly increased in group A compared with group V (from 0.42 to 1.11 MPa; P < 0.01). Energy dissipation was not significantly different among groups, although there was a trend toward higher values in group A for both directions. Histological assessments revealed no significant differences in collagen or elastic fibers among groups. In conclusion, aldosterone receptor inhibition altered the viscoelastic properties of the aortic wall in hyperlipidemic rabbits without detectable microscopic changes in elastic or collagen fibers, an effect that progressively might predispose to dilation and/or aneurysmal formation.
主动脉壁的动态力学紊乱可能导致主动脉进行性扩张，并可能导致动脉瘤形成。在这里，我们研究了以前未知的醛固酮抑制对高脂血症兔主动脉壁粘弹性的影响。36 只新西兰雄性兔，用标准饮食喂养四周，分为三组：对照组（C；n = 10），标准饮食；依普利酮（A；n = 12），高脂血症饮食加 100mg/kg/d 依普利酮（最后 4 周）；和载体（V；n = 14），高脂血症饮食（无依普利酮）。八周后，处死动物，从主动脉壁切取矩形条带，分别沿径向和轴向切割。在 37°C 下，将新鲜生理盐水湿润的条带在 1Hz 的频率下从 0 伸长至 20%的静息长度，进行周期性正弦伸长。测定动态生物力学粘弹性特征，“弹性蛋白相”低模量（E(L)）、“胶原相”高模量（E(H)）和耗散能指数。还对主动脉组织进行了组织学检查。依普利酮增加了醛固酮浓度，但不影响血压、胆固醇或钾浓度。与 C 组相比，A 组的 E(H)（从 3.40 降至 1.80MPa；P < 0.01）和 E(L)（从 0.46 降至 0.27MPa；P < 0.05）在径向方向显著降低。与 V 组相比，A 组在轴向方向的 E(L)显著增加（从 0.42 增至 1.11MPa；P < 0.01）。各组之间的能量耗散没有显著差异，尽管在两个方向上，A 组的能量耗散都有增加的趋势。组织学评估显示各组胶原纤维和弹性纤维无明显差异。结论：在高脂血症兔中，醛固酮受体抑制改变了主动脉壁的粘弹性特性，而弹性纤维和胶原纤维的微观变化无法检测到，这种效应可能逐渐导致扩张和/或动脉瘤形成。
