Miller V M, Komori K, Burnett J C, Vanhoutte P M
Department of Physiology and Biophysics, Mayo Graduate School of Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905.
Am J Physiol. 1989 Oct;257(4 Pt 2):H1127-31. doi: 10.1152/ajpheart.1989.257.4.H1127.
Experiments were designed to compare the sensitivity of venous and arterial smooth muscle to endothelin and to determine whether contractions to the peptide could be inhibited by endothelium-derived relaxing factor and nitric oxide. Rings of canine left anterior descending coronary, femoral, and mesenteric arteries and femoral and saphenous veins with and without endothelium were suspended for measurement of isometric force. In the presence of indomethacin, phentolamine, and propranolol, endothelin initiated concentration-dependent increases in tension in all rings. The veins were more sensitive to the peptide than were the arteries. Endothelin depolarized the smooth muscle of the saphenous veins and mesenteric arteries; the threshold concentration for depolarization was approximately 100 times lower in the veins (10(-10) M) than in the arteries (10(-8) M). Removal of the endothelium enhanced the sensitivity only of venous smooth muscle to endothelin. However, stimulation of the endothelium in the arteries with either acetylcholine or the calcium ionophore A23187 rapidly inhibited the maximal tension developed to the peptide. Nitric oxide inhibited contractions to endothelin in arteries and veins without endothelium; the inhibition was greater in the arteries than in the veins. These results indicate that venous smooth muscle is more sensitive than arterial smooth muscle to endothelin. In both blood vessels, endothelium-derived relaxing factor(s) can inhibit contractions to the peptide.
设计实验以比较静脉和动脉平滑肌对内皮素的敏感性，并确定内皮衍生舒张因子和一氧化氮是否能抑制对该肽的收缩反应。将有或无内皮的犬左前降支冠状动脉、股动脉、肠系膜动脉以及股静脉和大隐静脉的血管环悬挂起来，用于测量等长力。在吲哚美辛、酚妥拉明和普萘洛尔存在的情况下，内皮素使所有血管环的张力呈浓度依赖性增加。静脉对该肽比动脉更敏感。内皮素使大隐静脉和肠系膜动脉的平滑肌去极化；静脉去极化的阈值浓度（10⁻¹⁰ M）比动脉（10⁻⁸ M）低约100倍。去除内皮仅增强了静脉平滑肌对内皮素的敏感性。然而，用乙酰胆碱或钙离子载体A23187刺激动脉内皮可迅速抑制对该肽产生的最大张力。一氧化氮抑制无内皮的动脉和静脉对内皮素的收缩反应；动脉中的抑制作用比静脉中更大。这些结果表明，静脉平滑肌对内皮素比动脉平滑肌更敏感。在两种血管中，内皮衍生舒张因子均可抑制对该肽的收缩反应。
