Hoang T V, Choe E U, Lippton H L, Hyman A L, Flint L M, Ferrara J J
Department of Surgery, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA.
J Surg Res. 1996 Mar;61(2):330-8. doi: 10.1006/jsre.1996.0125.
To characterize the mesenteric alpha1- and alpha2-adrenoceptor populations in newborn piglets, an extracorporeal circuit was established to control intestinal blood flow in 0- to 2-day old and 10- to 14-day old animals. In both groups, alpha-adrenoceptor activation was first documented by observing dose-dependent increases in mesenteric perfusion pressure after intramesenteric arterial injection of alpha-adrenoceptor agonists. In the 10- to 14-day old piglets, mesenteric vasoconstrictor responses to alpha1-adrenoceptor agonists (methoxamine and norepinephrine) and an alpha2-adrenoceptor agonist (BHT-933) were each blunted (P < 0.05, analysis of variance) by peripheral intravenous injections of prazosin (an alpha1-adrenoceptor antagonist) and yohimbine (an alpha2-adrenoceptor antagonist), respectively. The mesenteric vasoconstrictor responses to those agonists were not significantly attenuated by prazosin or yohimbine in 0- to 2-day old animals, nor were they blunted by YM-12617 (alpha1-adrenoceptor antagonist) or idazoxan (alpha2-adrenoceptor antagonist)--compounds that are structurally unrelated to prazosin and yohimbine, respectively. In addition, mesenteric vasoconstrictor responses to other known vasoconstrictor agents--angiotensin II, neuropeptide Y, and a thromboxane A2 mimic (U-46619)--were not effected in either age group by prazosin or yohimbine, implying these agents act independently of alpha-adrenoceptor mechanisms. These data suggest that (1) there exists functional mesenteric alpha1- and alpha2-adrenoceptor-like activity in 10- to 14-day old piglets that, in 0- to 2-day old animals, is not specifically expressed; and (2) mesenteric alpha-adrenoceptor function becomes more selective as newborn piglets mature.
为了描述新生仔猪肠系膜α1和α2肾上腺素能受体群体的特征，建立了一个体外循环系统来控制0至2日龄和10至14日龄动物的肠道血流。在两组中，α肾上腺素能受体激活首先通过在肠系膜内动脉注射α肾上腺素能受体激动剂后观察到肠系膜灌注压的剂量依赖性增加来记录。在10至14日龄的仔猪中，肠系膜对α1肾上腺素能受体激动剂（甲氧明和去甲肾上腺素）和α2肾上腺素能受体激动剂（BHT - 933）的血管收缩反应分别被外周静脉注射哌唑嗪（一种α1肾上腺素能受体拮抗剂）和育亨宾（一种α2肾上腺素能受体拮抗剂）减弱（P < 0.05，方差分析）。在0至2日龄的动物中，哌唑嗪或育亨宾并未显著减弱肠系膜对这些激动剂的血管收缩反应，它们也未被YM - 12617（α1肾上腺素能受体拮抗剂）或咪唑克生（α2肾上腺素能受体拮抗剂）减弱，这两种化合物在结构上分别与哌唑嗪和育亨宾无关。此外，肠系膜对其他已知血管收缩剂——血管紧张素II、神经肽Y和血栓素A2类似物（U - 46619）——的血管收缩反应在两个年龄组中均未受到哌唑嗪或育亨宾的影响，这意味着这些药物的作用独立于α肾上腺素能受体机制。这些数据表明：（1）在10至14日龄的仔猪中存在功能性肠系膜α1和α2肾上腺素能受体样活性，而在0至2日龄的动物中未特异性表达；（2）随着新生仔猪的成熟，肠系膜α肾上腺素能受体功能变得更具选择性。
