Monos E, Lorant M, Feher E
Clinical Research Department, Semmelweis University of Medicine, Budapest, Hungary.
J Gravit Physiol. 1997 Jul;4(2):P39-40.
Frequent symptoms and serious complaints related to orthostatic intolerance are among the important reasons for investigating the long-term control mechanisms of blood vessels especially those of veins. Previously we studied perfused and superfused saphenous vein segments from rats maintained in head-up tilt position for two weeks. It was found that passive lumen capacity and acute pressure induced myogenic response of these vessels increased substantially without measurable change in wall thickness. Sympathetic component of the smooth muscle cell membrane potential determined in vivo was also significantly enhanced in this vein, but no such change was seen in the saphenous artery and in the brachial vessels. In a separate study, rarefaction of microvessels was found in the hind limb oxydative muscles after two-week tilting, while muscular water content was unaltered. These results suggest that long-term gravitational loading may induce adaptive rearrangement of the blood vessel functions. The aim of the present study was to quantitate and compare the density of nerve fiber terminals as well as their synaptic vesicle population in the wall of saphenous vein and artery from tilted rats to those obtained from rats which were maintained in horizontal, control position. It was hypothetized that adaptation of blood vessels to long-term gravitational loading might include also a morphological restructuring of the vascular adrenergic innervation.
与体位性不耐受相关的常见症状和严重主诉是研究血管尤其是静脉长期控制机制的重要原因之一。此前，我们研究了将大鼠保持头高位倾斜两周后其灌注和灌流的大隐静脉段。结果发现，这些血管的被动管腔容量和急性压力诱导的肌源性反应显著增加，而壁厚没有可测量的变化。在体内测定的平滑肌细胞膜电位的交感神经成分在该静脉中也显著增强，但在大隐动脉和肱血管中未观察到这种变化。在另一项研究中，发现倾斜两周后后肢氧化肌中的微血管稀疏，而肌肉含水量未改变。这些结果表明，长期重力负荷可能诱导血管功能的适应性重排。本研究的目的是定量并比较倾斜大鼠的大隐静脉和动脉壁中神经纤维终末的密度及其突触小泡数量，并与处于水平对照位置的大鼠的相应情况进行比较。据推测，血管对长期重力负荷的适应可能还包括血管肾上腺素能神经支配的形态学重构。
