Cardiovascular Physiology, Centre for Biomedicine and Medical Technology Mannheim, Ruprecht-Karls-University Heidelberg, Germany.
Cardiovasc Res. 2013 Sep 1;99(4):612-21. doi: 10.1093/cvr/cvt138. Epub 2013 May 31.
Functional remodelling takes place permanently in the circulatory system. Whether this process also affects the anti-contractile effect of the endothelium during vasoconstrictor action is unknown. Therefore, the hypothesis was tested that the impact of the anti-contractile effect of the endothelium on agonist-induced contractions changes during early postnatal development.
We studied isometric contractions in saphenous arteries of young (1-2 weeks) and adult (2-3 months) rats. Real-time PCR and western blot were performed to evaluate the levels of mRNA expression and protein phosphorylation, respectively. In young but not in adult rats, methoxamine-induced contractions of endothelium-intact vessels exhibited a lower sensitivity compared with endothelium-denuded vessels. The endothelial influence on methoxamine-induced contractions in arteries of young rats was completely blocked by inhibition of endothelial NO-synthase (eNOS) and guanylate cyclase. NO-donor-induced vessel relaxations were not different in young and adult rats. The expression level of eNOS mRNA was prominently higher in arteries from young compared with adult rats. eNOS inhibition alone induced tonic contractions of endothelium-intact arteries from young but not from adult animals that were associated with corresponding changes in phosphorylation of the myosin regulatory light chains, the regulatory subunit of smooth muscle cell myosin light chain phosphatase, and vasodilator-stimulated phosphoprotein, the latter two being considered to be good markers of NO/sGC/PKG pathway activity.
We demonstrated that agonist-induced contractions in arteries of young rats are attenuated by the endothelium possessing an active NO-pathway. The active NO-pathway is due to a constitutive eNOS activity that disappears with age.
循环系统会发生永久性的功能重塑。目前尚不清楚这一过程是否会影响血管收缩时内皮的抗收缩作用。因此，本研究假设内皮的抗收缩作用对激动剂诱导收缩的影响在出生后早期发育过程中会发生变化。
我们研究了幼鼠（1-2 周）和成年鼠（2-3 个月）的隐静脉等长收缩。实时 PCR 和 Western blot 分别用于评估 mRNA 表达和蛋白磷酸化水平。与去内皮血管相比，在幼鼠但不在成年鼠中，甲氧胺诱导的完整内皮血管收缩的敏感性较低。内皮一氧化氮合酶（eNOS）和鸟苷酸环化酶抑制剂完全阻断了幼鼠血管中甲氧胺诱导的内皮收缩。幼鼠和成年鼠的 NO 供体诱导的血管舒张没有差异。与成年鼠相比，幼鼠动脉中 eNOS mRNA 的表达水平明显更高。eNOS 抑制剂单独诱导幼鼠完整内皮血管的紧张性收缩，但在成年动物中没有诱导这种收缩，这与肌球蛋白调节轻链、平滑肌细胞肌球蛋白轻链磷酸酶的调节亚基和血管扩张刺激磷蛋白的磷酸化相应变化相关，后两者被认为是 NO/sGC/PKG 通路活性的良好标志物。
我们证明了幼鼠动脉中激动剂诱导的收缩被具有活性 NO 通路的内皮所减弱。该活性 NO 通路归因于组成型 eNOS 活性，这种活性会随着年龄的增长而消失。
