Hayashida N, Okui K, Fukuda Y
Jpn J Physiol. 1987;37(2):183-96. doi: 10.2170/jjphysiol.37.183.
Possible roles of smooth muscle contractions in the vascular dynamics were studied in the isolated rat large artery which has previously been shown to generate spontaneous rhythmic contractions depending upon the extracellular Ca2+. A cylindrical segment of the common carotid artery was superfused externally and perfused intraluminally by Tyrode solution, and the steady state intraluminal pressure (P)-volume (V) relationship of the vessel was obtained. The pressure buffering characteristic (Windkessel effect) of the vascular wall was evaluated by measuring the intraluminal pressure swing during application of external alternating pressure (semi-triangular pressure pulse, 0-120 mmHg, 300 cycle/min, "dynamic pressure load") to the intraluminal space. Effects on these vascular dynamics of inhibition of spontaneous smooth muscle contraction during superfusion of the preparation with nominally Ca2+-free Tyrode solution were investigated. Spontaneous rhythmic fluctuations of the intraluminal pressure (0.2-1.0 mmHg, 2-25 cycle/min), presumably due to contractions of vascular smooth muscles, were detected. The Ca2+-free solution abolished these spontaneous changes in the intraluminal pressure and reduced the baseline intraluminal pressure. The volume distensibility (delta V/(V X delta P] of the preparation at higher intraluminal fluid volumes (or pressures, higher wall stretch) was increased by Ca2+-free solution. The magnitude of intraluminal pressure swing and the maximum rate of changes in the pressure during application of "dynamic pressure load" were decreased in Ca2+-free solution. The results suggest that the inhibition of spontaneous contractions of smooth muscle by Ca2+-free solution may increase the volume distensibility and pressure-buffering function of the large elastic artery.
在先前已证明可依赖细胞外钙离子产生自发性节律性收缩的离体大鼠大动脉中，研究了平滑肌收缩在血管动力学中的可能作用。将一段颈总动脉制成圆柱形，外部用台氏液灌流，管腔内也用台氏液灌注，从而获得血管的稳态管腔内压力（P）-容积（V）关系。通过测量向管腔内施加外部交变压力（半三角压力脉冲，0 - 120 mmHg，300次/分钟，“动态压力负荷”）期间的管腔内压力波动，评估血管壁的压力缓冲特性（风箱效应）。研究了在制备物用名义上无钙离子的台氏液灌流期间抑制自发性平滑肌收缩对这些血管动力学的影响。检测到管腔内压力的自发性节律波动（0.2 - 1.0 mmHg，2 - 25次/分钟），推测这是由于血管平滑肌收缩所致。无钙离子溶液消除了管腔内压力的这些自发性变化，并降低了基线管腔内压力。在较高管腔内液体容积（或压力，较高壁张力）下，制备物的容积扩张性（ΔV/(V×ΔP)）因无钙离子溶液而增加。在无钙离子溶液中，“动态压力负荷”施加期间管腔内压力波动的幅度和压力变化的最大速率降低。结果表明，无钙离子溶液抑制平滑肌的自发性收缩可能会增加大弹性动脉的容积扩张性和压力缓冲功能。
