Frøbert O, Mikkelsen E O, Bagger J P
Department of Cardiology, University Hospital Aarhus, Skejby Sygehus, Denmark.
Acta Physiol Scand. 1999 Apr;165(4):379-85. doi: 10.1046/j.1365-201x.1999.00519.x.
The aim of the study was to investigate transmural pressure and longitudinal stretch modulation of K+- and Ca2+-induced constriction of porcine conductance coronary arteries. In a pressure myograph set-up, left anterior descendent coronary arteries from 70 to 90 kg pigs were investigated at pressures from 20 to 120 mmHg. Longitudinal extension ratio (lambda = L/L0(-1), where L0 is the in situ length and L the examination length) varied between 0.9 and 1.1. Two protocols were carried out: (1) Outer diameter response to maximal depolarization by K+ 125 mM at 20-120 mmHg and lambda at 0.90-1.10. (2) Concentration-response curves with K+ (4.7-125 mM) and Ca2+ (0.05-4.0 mM) at four combinations of P and lambda (P = 100 mmHg, lambda = 0.9; P = 100 mmHg, lambda = 1.1; P = 40 mmHg, lambda = 0.9; p = 40 mmHg, lambda = 1.1).
Endothelial function was preserved. A slight (<5% diameter reduction) basal tone and no myogenic response was found. Protocol 1: the constriction to K+ 125 mM was maximal in a wide pressure range from 40 to 120 mmHg. Despite the fact that K+-induced diameter changes were statistically insignificant between 40 and 120 mmHg, there was a linear trend towards smaller diameter changes in this pressure range (r = -0.54, P < 0.01). Stretch influenced constriction at 20 mmHg because lambda = 0.90 and 0.95 resulted in smaller diameter-reductions than lambda = 1.00-1.10 (P < 0.05 for all). Contrastingly, at 120 mmHg the constriction at lambda = 1.10 was smaller than the responses at lambda = 0.90-1.05 (P < 0.05 for all). Protocol 2: EC50 and EC10 values for K+- and Ca2+ were generally higher (more sensitive) at 40 compared with 100 mmHg. Stretch was of no significant importance for EC50 and EC10 at 40 and 100 mmHg. It is concluded that porcine coronary artery constriction to non-metabolized agonists is maximal at 40 mmHg with a trend towards smaller diameter changes with higher pressures. Longitudinal stretch affects responsiveness at pressure extremes.
本研究的目的是调查跨壁压力和纵向拉伸对猪传导性冠状动脉K⁺和Ca²⁺诱导收缩的调节作用。在压力肌动描记仪设置中，对体重70至90千克猪的左前降支冠状动脉在20至120 mmHg的压力下进行研究。纵向延伸率（λ = L/L₀ - 1，其中L₀是原位长度，L是检查长度）在0.9至1.1之间变化。进行了两个方案：（1）在20至120 mmHg和λ为0.90至1.10时，对125 mM K⁺最大去极化的外径反应。（2）在P和λ的四种组合（P = 100 mmHg，λ = 0.9；P = 100 mmHg，λ = 1.1；P = 40 mmHg，λ = 0.9；P = 40 mmHg，λ = 1.1）下，用K⁺（4.7至125 mM）和Ca²⁺（0.05至4.0 mM）绘制浓度 - 反应曲线。
内皮功能得以保留。发现存在轻微的（直径减少<5%）基础张力且无肌源性反应。方案1：在40至120 mmHg的宽压力范围内，对125 mM K⁺的收缩作用最大。尽管在40至120 mmHg之间K⁺诱导的直径变化在统计学上无显著差异，但在该压力范围内存在直径变化较小的线性趋势（r = -0.54，P < 0.01）。拉伸在20 mmHg时影响收缩，因为λ = 0.90和0.95导致的直径减少比λ = 1.00 - 1.10时小（所有情况P < 0.05）。相反，在120 mmHg时，λ = 1.10时的收缩小于λ = 0.90 - 1.05时的反应（所有情况P < 0.05）。方案2：与100 mmHg相比，40 mmHg时K⁺和Ca²⁺的EC50和EC10值通常更高（更敏感）。在40和100 mmHg时，拉伸对EC50和EC10无显著影响。结论是，猪冠状动脉对非代谢性激动剂的收缩在40 mmHg时最大，随着压力升高直径变化有减小的趋势。纵向拉伸在压力极值时影响反应性。
