Lin P J, Chang C H, Pearson P J, Tzen K Y, Chu J J, Chang J P, Hsieh M J
Thoracic and Cardiovascular Surgery, Chang Gung Memorial Hospital, Taipei, Taiwan, ROC.
Ann Thorac Surg. 1993 Jul;56(1):97-100. doi: 10.1016/0003-4975(93)90409-b.
The internal mammary artery (IMA) has become the conduct of choice for coronary artery bypass grafting. However, the IMA graft can exhibit vasoconstriction during the perioperative period. Experiments were designed to determine the role of cyclooxygenase products in human IMA during hypoxia. Rings of IMA, with and without endothelium, were suspended in organ baths containing physiologic salt solution. Rings were contracted with norepinephrine and then exposed to hypoxia for 15 minutes. In segments with endothelium, hypoxia induced a transient relaxation followed by contraction. This contraction was associated with a significantly increased production of thromboxane B2, the stable metabolite of thromboxane A2 (n = 10; from 120.7 +/- 3.5 pg/mg wet tissue before hypoxia to 175.8 +/- 5.2 pg/mg during hypoxia; p < 0.05). This hypoxic contraction could be attenuated by indomethacin. However, thromboxane B2 could not be detected in samples from organ baths containing IMA segments without endothelium before or during hypoxia. This study demonstrated that endothelium of human IMA grafts releases thromboxane A2 basally and that production is augmented by hypoxia, which acts to constrict the underlying vascular smooth muscle, increase vascular tone, and promote ischemic events such as vasospasm and thrombosis, particularly in hypoxemic patients.
乳内动脉（IMA）已成为冠状动脉旁路移植术的首选血管。然而，IMA移植物在围手术期可出现血管收缩。本实验旨在确定环氧化酶产物在缺氧状态下人IMA中的作用。将有内皮和无内皮的IMA血管环悬挂于含有生理盐溶液的器官浴槽中。血管环先用去甲肾上腺素收缩，然后暴露于缺氧环境15分钟。在有内皮的节段中，缺氧诱导短暂舒张，随后收缩。这种收缩与血栓素B2（血栓素A2的稳定代谢产物）的生成显著增加有关（n = 10；缺氧前为120.7±3.5 pg/mg湿组织，缺氧时为175.8±5.2 pg/mg；p < 0.05）。这种缺氧收缩可被吲哚美辛减弱。然而，在缺氧前后，含有无内皮IMA节段的器官浴槽样本中均未检测到血栓素B2。本研究表明，人IMA移植物的内皮细胞基础状态下释放血栓素A2，缺氧时其生成增加，这会导致其下的血管平滑肌收缩、血管张力增加，并促进诸如血管痉挛和血栓形成等缺血事件，尤其是在低氧血症患者中。
