Gao Yuansheng, Dhanakoti Srinivas, Trevino Earleen M, Sander Fred C, Portugal Ada M, Raj J Usha
Harbor-UCLA Medical Center, Research and Education Institute, 1124 W. Carson St., RB-1, Torrance, CA 90502, USA.
Am J Physiol Lung Cell Mol Physiol. 2003 Sep;285(3):L611-8. doi: 10.1152/ajplung.00411.2002. Epub 2003 May 16.
Cyclic GMP-dependent protein kinase (PKG) plays an important role in regulating pulmonary vasomotor tone in the perinatal period. In this study, we tested the hypothesis that a change in oxygen tension affects PKG-mediated pulmonary vasodilation. Isolated intrapulmonary arteries and veins of near-term fetal lambs were first incubated for 4 h under hypoxic and normoxic conditions (Po2 of 30 and 140 mmHg, respectively) and then contracted with endothelin-1. 8-Bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP), a cell membrane-permeable analog of cGMP, induced a greater relaxation in vessels incubated in normoxia than in hypoxia. beta-Phenyl-1,N2-etheno-8-bromoguanosine-3',5'-cyclic monophosphorothioate, Rp isomer (Rp-8-Br-PET-cGMPS), a selective inhibitor of PKG, attenuated relaxation induced by 8-BrcGMP (10-4 and 3 x 10-4 M). In the presence of Rp-8-Br-PET-cGMPS, the differential responses to 8-BrcGMP between hypoxia and normoxia treatment were abolished in veins but not in arteries. cGMP-stimulated PKG activity was present in arteries but not in veins after 4 h of hypoxia. Both vessel types showed significant increase in cGMP-stimulated PKG activity after 4 h of normoxia. PKG protein (Western blot analysis) and PKG mRNA levels (quantitative RT-PCR) were greater in veins but not in arteries after 4-h exposure to normoxia vs. hypoxia. These results demonstrate that oxygen augments cGMP-mediated vasodilation of fetal pulmonary arteries and veins. Furthermore, the effect of oxygen on response of the veins to cGMP is due to an increase in the activity, protein level, and mRNA of PKG.
环磷酸鸟苷依赖性蛋白激酶（PKG）在围产期调节肺血管张力中起重要作用。在本研究中，我们检验了氧张力变化影响PKG介导的肺血管舒张这一假说。首先将近足月胎羊的肺内动脉和静脉分离出来，在低氧和常氧条件下（分别为30和140 mmHg的氧分压）孵育4小时，然后用内皮素-1使其收缩。8-溴鸟苷3',5'-环一磷酸（8-BrcGMP）是一种可透过细胞膜的cGMP类似物，在常氧孵育的血管中比在低氧孵育的血管中诱导出更大程度的舒张。PKG的选择性抑制剂β-苯基-1,N2-乙烯基-8-溴鸟苷-3',5'-环一磷酸硫代磷酸酯，Rp异构体（Rp-8-Br-PET-cGMPS）减弱了8-BrcGMP（10-4和3×10-4 M）诱导的舒张。在Rp-8-Br-PET-cGMPS存在的情况下，低氧和常氧处理之间对8-BrcGMP的差异反应在静脉中消失，但在动脉中未消失。低氧4小时后，cGMP刺激的PKG活性存在于动脉中但不存在于静脉中。常氧4小时后，两种血管类型的cGMP刺激的PKG活性均显著增加。与低氧相比，常氧暴露4小时后，静脉中的PKG蛋白（蛋白质印迹分析）和PKG mRNA水平（定量逆转录PCR）更高，但动脉中并非如此。这些结果表明，氧增强了cGMP介导的胎儿肺动静脉舒张。此外，氧对静脉对cGMP反应的影响是由于PKG的活性、蛋白水平和mRNA增加。
