Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
Am J Physiol Regul Integr Comp Physiol. 2012 Aug 15;303(4):R368-75. doi: 10.1152/ajpregu.00490.2011. Epub 2012 Jun 27.
Myogenic tone (MT) is a primary modulator of blood flow in the resistance vasculature of the brain, kidney, skeletal muscle, and perhaps in other high-flow organs such as the pregnant uterus. MT is known to be regulated by endothelium-derived factors, including products of the nitric oxide synthase (NOS) and/or the cyclooxygenase (COX) pathways. We asked whether pregnancy influenced MT in myometrial arteries (MA), and if so, whether such an effect could be attributed to alterations in NOS and/or COX. MA (200-300 μm internal diameter, 2-3 mm length) were isolated from 10 nonpregnant and 12 pregnant women undergoing elective hysterectomy or cesarean section, respectively. In the absence of NOS and/or COX inhibition, pregnancy was associated with increased MT in endothelium-intact MA compared with MA from nonpregnant women (P < 0.01). The increase in MT was not due to increased Ca(2+) entry via voltage-dependent channels since both groups of MA exhibited similar levels of constriction when exposed to 50 mM KCl. NOS inhibition (N(ω)-nitro-L-arginine methyl ester, L-NAME) or combined NOS/COX inhibition (L-NAME/indomethacin) increased MT in MA from pregnant women (P = 0.001 and P = 0.042, respectively) but was without effect in arteries from nonpregnant women. Indomethacin alone was without effect on MT in MA from either nonpregnant or pregnant women. We concluded that MT increases in MA during human pregnancy and that this effect was partially opposed by enhanced NOS activity.
肌源性张力（MT）是大脑、肾脏、骨骼肌等阻力血管中血流的主要调节因子，也许在其他高流量器官如孕妇子宫中也是如此。已知 MT 受内皮衍生因子调节，包括一氧化氮合酶（NOS）和/或环氧化酶（COX）途径的产物。我们询问了妊娠是否会影响子宫肌层动脉（MA）中的 MT，如果是，这种影响是否可以归因于 NOS 和/或 COX 的改变。分别从 10 名非妊娠和 12 名接受择期子宫切除术或剖宫产术的妊娠妇女中分离出 200-300μm 内径、2-3mm 长度的 MA。在没有 NOS 和/或 COX 抑制的情况下，与非妊娠妇女的 MA 相比，妊娠时完整内皮的 MA 中的 MT 增加（P<0.01）。MT 的增加不是由于通过电压依赖性通道增加 Ca2+进入引起的，因为两组 MA 在暴露于 50mM KCl 时表现出相似的收缩水平。NOS 抑制（N（ω）-硝基-L-精氨酸甲酯，L-NAME）或联合 NOS/COX 抑制（L-NAME/吲哚美辛）增加了妊娠妇女 MA 中的 MT（P=0.001 和 P=0.042，分别），但对非妊娠妇女的动脉无影响。单独使用吲哚美辛对非妊娠或妊娠妇女的 MA 中的 MT 均无影响。我们得出结论，在人类妊娠期间，MA 中的 MT 增加，这种效应部分被增强的 NOS 活性所抵消。
