Wilson R A, Di Mario C, Krams R, Soei L K, Wenguang L, Laird A C, The S H, Gussenhoven E, Verdouw P, Roelandt J R
Cardiology Division, Oregon Health Sciences University, Portland 97201, USA.
Angiology. 1995 Jun;46(6):481-8. doi: 10.1177/000331979504600604.
The presence of smooth muscle fibers on the wall of large arteries would suggest that arterial compliance might change in response to vasoactive substances. The purpose of this study is to determine the basal level of vasomotor tone in these arteries in a commonly used animal preparation and to learn whether the compliance of large conductance arteries can be altered in vivo by vasoactive agents.
Proximal iliac arterial compliance was measured in 7 pentobarbital-anesthetized pigs, before and during local infusions of adenosine and norepinephrine. Luminal area was measured every forty milliseconds by means of a 30 MHz intravascular ultrasound catheter and an automatic edge detection program. Simultaneous high-fidelity pressure measurements were obtained by means of a catheter-tipped pressure microtransducer positioned at the origin of the iliac artery. Linear regression analysis of the area/pressure relationship in two consecutive cardiac cycles (systolic phase only) was performed before and during adenosine and norepinephrine infusions. The slope of the area/pressure regression line was defined as an index of arterial compliance. Measurements after three minutes of infusions of adenosine (5-5000 micrograms/minute) and norepinephrine (0.001-10 micrograms/minute) were compared with the control measurements.
Even at the highest infusion rate, adenosine did not significantly increase arterial compliance as compared with baseline (25 +/- 7 vs 19 +/- 4 mm2/mmHg x 10(-3), respectively, P = ns). In contrast, norepinephrine decreased arterial compliance as compared with the second baseline control (13 +/- 3 vs 20 +/- 3 mm2/mmHg x 10(-3), respectively, P < 0.01).
In this animal model with pentobarbital anesthesia, arterial compliance may be modified more by the acute infusion of norepinephrine than by adenosine in large conductance arteries such as the proximal iliac. Thus, in this preparation, smooth muscle tone tends to be minimal and arterial compliance near maximal (ie, mostly a passive phenomenon). However, in response to norepinephrine, arterial compliance can decrease significantly as smooth muscle tone increases. Intravascular ultrasound allows continuous and accurate monitoring of these changes of arterial dimensions, suggesting that this technique may be useful in the evaluation of pharmacologically induced changes in the compliance of large arteries by vasoactive agents.
大动脉壁上存在平滑肌纤维，这表明动脉顺应性可能会因血管活性物质而改变。本研究的目的是在一种常用的动物实验准备中确定这些动脉的血管运动张力基础水平，并了解大传导动脉的顺应性在体内是否会被血管活性药物改变。
在7只戊巴比妥麻醉的猪身上，在局部输注腺苷和去甲肾上腺素之前及期间测量近端髂动脉顺应性。通过30MHz血管内超声导管和自动边缘检测程序每40毫秒测量一次管腔面积。通过置于髂动脉起始处的导管尖端压力微传感器同时获得高保真压力测量值。在输注腺苷和去甲肾上腺素之前及期间，对两个连续心动周期（仅收缩期）的面积/压力关系进行线性回归分析。面积/压力回归线的斜率被定义为动脉顺应性指标。将输注腺苷（5 - 5000微克/分钟）和去甲肾上腺素（0.001 - 10微克/分钟）三分钟后的测量值与对照测量值进行比较。
即使在最高输注速率下，与基线相比，腺苷也未显著增加动脉顺应性（分别为25±7与19±4平方毫米/毫米汞柱×10⁻³，P =无显著差异）。相比之下，与第二个基线对照相比，去甲肾上腺素降低了动脉顺应性（分别为13±3与20±3平方毫米/毫米汞柱×10⁻³，P < 0.01）。
在这种戊巴比妥麻醉的动物模型中，在诸如近端髂动脉等大传导动脉中，动脉顺应性可能更多地被去甲肾上腺素的急性输注而非腺苷所改变。因此，在这种准备中，平滑肌张力趋于最小，动脉顺应性接近最大（即，主要是一种被动现象）。然而，对去甲肾上腺素的反应中，随着平滑肌张力增加，动脉顺应性会显著降低。血管内超声允许连续且准确地监测动脉尺寸的这些变化，表明该技术可能有助于评估血管活性药物对大动脉顺应性的药理学诱导变化。
