Hamel Christine, Millette Esther, Lamontagne Daniel
Faculté de Pharmacie, Université de Montréal, C.P. 6128, Succursale centre-ville, Montréal, QC, Canada H3C 3J7.
Life Sci. 2005 Jul 22;77(10):1069-81. doi: 10.1016/j.lfs.2004.12.039. Epub 2005 Apr 25.
The contribution of endothelium-derived mediators and protein kinase C in the tachyphylaxis to arginine vasopressin (AVP) was assessed in the rat aorta. Endothelium-intact (E+) and denuded rings (E-) obtained from the rat thoracic aorta were exposed to three administrations of a supramaximal concentration of AVP (100 nM), lasting 20 min and 45 min apart. N-Omega-nitro-L-arginine (NNLA), a non-selective inhibitor of all isoforms of NO synthase, and AMT, a selective inhibitor for the inducible (iNOS) and neuronal (nNOS) isoforms, diminished the tachyphylaxis to AVP significantly in both E+ and in E- rings. No iNOS could be detected by Western blots in freshly isolated rings or in rings exposed to AVP, despite a strong signal in rings isolated from LPS-treated rats, while nNOS could be constitutively detected. Inhibition of prostaglandins or epoxyeicosatrienoic acids (EETs) synthesis by diclofenac or clotrimazole, respectively, had no effect on tachyphylaxis while combination of these agents diminished tachyphylaxis in E+ only. Combination of NNLA, diclofenac and clotrimazole blocked completely the tachyphylaxis. Inhibition of PKC by either chelerythrine or bisindolylmaleimide I-HCl (BisI) led to a significant diminution of AVP tachyphylaxis only in E-. Activation of PKC with phorbol-12-myristate-13-acetate (PMA) simulated tachyphylaxis to AVP in E- only, effect blocked by the NO donor, SNP. In conclusion, NO produced from constitutive nNOS present in vascular smooth muscle cells participates in tachyphylaxis to AVP. PKC is involved in this tachyphylaxis only in E- rings, the presence of NO probably diminishing the effects of this kinase.
在大鼠主动脉中评估了内皮衍生介质和蛋白激酶C在对精氨酸加压素（AVP）快速耐受性中的作用。从大鼠胸主动脉获取的完整内皮（E+）和去内皮环（E-）暴露于三次超最大浓度的AVP（100 nM），每次给药持续20分钟，间隔45分钟。N-ω-硝基-L-精氨酸（NNLA）是一氧化氮合酶所有同工型的非选择性抑制剂，AMT是诱导型（iNOS）和神经元型（nNOS）同工型的选择性抑制剂，二者均显著降低了E+环和E-环对AVP的快速耐受性。尽管从脂多糖处理的大鼠分离的环中有很强的信号，但在新鲜分离的环或暴露于AVP的环中，通过蛋白质印迹法未检测到iNOS，而nNOS可组成性检测到。分别用双氯芬酸或克霉唑抑制前列腺素或环氧二十碳三烯酸（EETs）的合成对快速耐受性没有影响，而这些药物联合使用仅在E+环中降低了快速耐受性。NNLA、双氯芬酸和克霉唑联合使用完全阻断了快速耐受性。用白屈菜红碱或双吲哚马来酰亚胺I-HCl（BisI）抑制蛋白激酶C仅在E-环中导致AVP快速耐受性显著降低。用佛波醇-12-肉豆蔻酸酯-13-乙酸酯（PMA）激活蛋白激酶C仅在E-环中模拟了对AVP的快速耐受性，该作用被一氧化氮供体硝普钠（SNP）阻断。总之，血管平滑肌细胞中组成性存在的nNOS产生的一氧化氮参与了对AVP的快速耐受性。蛋白激酶C仅在E-环中参与这种快速耐受性，一氧化氮的存在可能减弱了该激酶的作用。
