Bird I M, Zheng J, Cale J M, Magness R R
Department of Obstetrics and Gynecology, University of Wisconsin, Madison 53715, USA.
Endocrinology. 1997 Jan;138(1):490-8. doi: 10.1210/endo.138.1.4879.
During pregnancy, the uterine artery demonstrates refractoriness to vasoconstriction by infused angiotensin II (AII). AII increases prostacyclin (PGI2) production by uterine artery endothelium from pregnant ewes, and this response is mediated via the AT1 receptor (AT1-R). This response is also unique to pregnancy because AII does not stimulate PGI2 production by uterine artery endothelium from nonpregnant ewes. We therefore hypothesize that the increase in uterine artery PGI2 production in response to AII in pregnancy is associated in part with a concomitant increase in AT1-R expression in uterine artery endothelium. Endothelium-derived protein was directly removed from the lumenal surface of freshly isolated uterine and systemic (omental) arteries from nonpregnant and pregnant ewes. AT1-R expression was then measured in both the endothelium-derived fraction and endothelium-denuded vascular smooth muscle (VSM) fraction by Western analysis. AT1-R was detected as 54- and 65-kDa proteins in all samples, as well as adrenal cortex control. AT1-R expression increased more than 8-fold in uterine artery endothelium of pregnant ewes over that in nonpregnant ewes at each of four gestational ages (P < 0.05 at 110, 120, 130, 142 days, n = 4 each vs. n = 6 nonpregnant). No significant differences were seen, however, from 110 to 142 days of gestation. In contrast, whereas the level of AT1-R staining in omental artery endothelium in nonpregnant ewes was higher than in uterine artery, AT1-R increased less in pregnant ewes (2-fold) and only reached significance over nonpregnant values at 110 and 120 days, or when data was combined irrespective of gestational age (P < 0.05). Although AT1-R was also detected in uterine and omental artery VSM, little or no change in expression was observed in pregnancy. Results were confirmed by immunohistochemical staining of arterial cross sections, and the increase in AT1-R expression in uterine artery endothelium was confirmed by RT/PCR amplification of AT1-R messenger RNA from collagenase dispersed cells (n = 4 pregnant vs. n = 4 nonpregnant, mean 20-fold increase, P < 0.028). We conclude that increased uterine artery endothelial PGI2 responsiveness to AII during pregnancy is indeed associated with a correspondingly marked and localized increase in expression of the endothelial AT1-R receptor. We believe our findings allow a more detailed understanding of the molecular mechanisms that underlie increased uterine blood flow that is so central to the normal development of the growing fetus, and on dysfunction may lead to conditions such as preeclampsia.
在妊娠期间，子宫动脉对输注的血管紧张素II（AII）表现出血管收缩抵抗性。AII可增加妊娠母羊子宫动脉内皮细胞中前列环素（PGI2）的生成，且这种反应是通过1型血管紧张素受体（AT1-R）介导的。这种反应也是妊娠所特有的，因为AII不会刺激非妊娠母羊子宫动脉内皮细胞生成PGI2。因此，我们推测妊娠期间子宫动脉对AII反应性增强，PGI2生成增加，部分原因是子宫动脉内皮细胞中AT1-R表达随之增加。直接从非妊娠和妊娠母羊新鲜分离的子宫动脉和体循环（网膜）动脉的管腔表面去除内皮衍生蛋白。然后通过蛋白质免疫印迹分析测量内皮衍生部分和去内皮的血管平滑肌（VSM）部分中的AT1-R表达。在所有样品以及肾上腺皮质对照中，AT1-R被检测为54 kDa和65 kDa的蛋白质。在四个胎龄中的每一个胎龄时，妊娠母羊子宫动脉内皮中的AT1-R表达比非妊娠母羊增加超过8倍（在妊娠110、120、130、142天时P <\u20090.05，每组n = 4只妊娠母羊与n = 6只非妊娠母羊相比）。然而，在妊娠110至142天期间未观察到显著差异。相比之下，虽然非妊娠母羊网膜动脉内皮中的AT1-R染色水平高于子宫动脉，但妊娠母羊中AT1-R的增加较少（2倍），仅在妊娠110和120天时或无论胎龄合并数据时才显著高于非妊娠母羊的值（P <\u20090.05）。虽然在子宫和网膜动脉VSM中也检测到AT1-R，但在妊娠期间未观察到表达有明显变化。通过动脉横截面的免疫组织化学染色证实了结果，并且通过对胶原酶分散细胞中AT1-R信使RNA的RT/PCR扩增证实了子宫动脉内皮中AT1-R表达的增加（n = 4只妊娠母羊与n = 4只非妊娠母羊相比，平均增加20倍，P <\u20090.028）。我们得出结论，妊娠期间子宫动脉内皮对AII的PGI2反应性增加确实与内皮AT1-R受体表达相应显著且局部增加有关。我们相信我们的发现有助于更详细地了解子宫血流增加的分子机制，这对胎儿的正常发育至关重要，功能障碍可能导致子痫前期等病症。
