Gregg A R, Thompson L P, Herrig J E, Weiner C P
Department of Obstetrics and Gynecology, University of Iowa College of Medicine, Iowa City 52242-1080, USA.
J Vasc Res. 1995 Mar-Apr;32(2):106-11. doi: 10.1159/000159083.
Regional variation in the response of the thoracic aorta to contractile agonists has previously been demonstrated. Since the net contractile response reflects the interaction between smooth muscle activation and the release of endothelial substances, we hypothesize that agonist-stimulated release of endothelium-derived nitric oxide (NO) also varies along the length of the thoracic aorta. The distribution of thoracic aorta estrogen receptors is also regionalized. Since pregnancy augments the release of endothelium-derived NO by acetylcholine (ACh) in some arterial beds, we further hypothesize that pregnancy enhances the stimulated release of NO from the thoracic aorta. Aortae were removed from nonpregnant and near term pregnant guinea pigs and cut into ring segments numbered sequentially proximal to distal. The rings were suspended at their optimal passive tension and submaximally contracted with prostaglandin F2 alpha. Endothelium-derived NO-dependent relaxation to ACh increased moving proximal to distal along the aorta independent of pregnancy and ACh relaxation was unaffected by pretreatment with physostigmine to inhibit cholinesterase. The magnitude of the relaxation to carbachol among the different segments was similar to ACh. Pregnancy decreased the ED50 for ACh of segments from the middle and distal segments of the thoracic aorta. Relaxation to the NO donor sodium nitroprusside and the nonreceptor-mediated endothelium-dependent relaxing agent A23187 was uniform along the length of the aorta and independent of pregnancy. These experiments demonstrate regional variation in the stimulated release of endothelium-derived NO in the guinea pig thoracic aorta which is increased by pregnancy.
先前已证实胸主动脉对收缩激动剂的反应存在区域差异。由于净收缩反应反映了平滑肌激活与内皮物质释放之间的相互作用，我们推测激动剂刺激的内皮源性一氧化氮（NO）释放也会沿胸主动脉的长度发生变化。胸主动脉雌激素受体的分布也呈区域化。由于妊娠会增强某些动脉床中乙酰胆碱（ACh）刺激的内皮源性NO释放，我们进一步推测妊娠会增强胸主动脉刺激的NO释放。从未怀孕和接近足月妊娠的豚鼠身上取出主动脉，并切成从近端到远端依次编号的环段。将环段以其最佳被动张力悬挂，并用前列腺素F2α进行亚最大收缩。内皮源性NO依赖的对ACh的舒张作用沿主动脉从近端到远端增加，与妊娠无关，且ACh舒张不受毒扁豆碱预处理抑制胆碱酯酶的影响。不同节段对卡巴胆碱的舒张幅度与ACh相似。妊娠降低了胸主动脉中、远端节段对ACh的半数有效剂量（ED50）。对NO供体硝普钠和非受体介导的内皮依赖性舒张剂A23187的舒张作用在主动脉全长上是均匀的，且与妊娠无关。这些实验证明了豚鼠胸主动脉中内皮源性NO刺激释放的区域差异，妊娠会使其增加。
