Oriji G K, Keiser H R
Hypertension-Endocrine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Am J Physiol. 1996 Jul;271(1 Pt 1):C398-404. doi: 10.1152/ajpcell.1996.271.1.C398.
Endothelin (ET) is a potent vasoconstrictor peptide that induces characteristically long-lasting contractions. We used both intact and endothelium-denuded rat aortic rings to investigate the role of protein kinase C (PKC) in ET-induced contractions. ET (10(-9) M) and phorbol 12,13-dibutyrate (PDBu), a PKC activator, produced a gradual and sustained contraction of greater magnitude in denuded aortic rings than in intact rings. When aortic rings were pretreated with graded concentrations of different PKC inhibitors, inhibition of ET-induced contractions began at 10(-9)M and was nearly complete at 10(-3)M, and the reduction was greater in intact than in denuded rings. Pretreatment of aortic rings with PDBu or NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase, potentiated ET-induced contractions. PKC enzyme assay showed activation of PKC in aortic rings that were treated with either ET or PDBu, inhibition after pretreatment with PKC inhibitors, and no change with 4 alpha-phorbol 12,13-didecanoate (PDD), an inactive phorbol ester. ET significantly increased nitrate and nitrite production, which was further increased by pretreatment with PKC inhibitors. PDBu prevented ET-induced nitrate/nitrite production, and PDD had no effect. These results strongly suggest that PKC mediates, in part, ET-induced contractions in rat aortic rings and that an intact endothelium is required for maximum inhibition by PKC inhibitors because PKC stimulated by ET inhibits nitric oxide release.
内皮素（ET）是一种强效血管收缩肽，可诱导特征性的持久收缩。我们使用完整的和内皮剥脱的大鼠主动脉环来研究蛋白激酶C（PKC）在ET诱导的收缩中的作用。ET（10⁻⁹ M）和PKC激活剂佛波醇12,13 - 二丁酸酯（PDBu）在剥脱的主动脉环中产生的逐渐且持续的收缩幅度大于完整环。当用不同浓度梯度的PKC抑制剂预处理主动脉环时，对ET诱导收缩的抑制在10⁻⁹ M开始，在10⁻³ M时几乎完全抑制，并且完整环中的减少幅度大于剥脱环。用PDBu或一氧化氮合酶抑制剂NG - 硝基 - L - 精氨酸甲酯（L - NAME）预处理主动脉环可增强ET诱导的收缩。PKC酶活性测定显示，用ET或PDBu处理的主动脉环中PKC被激活，用PKC抑制剂预处理后被抑制，而用无活性的佛波醇酯4α - 佛波醇12,13 - 二癸酸酯（PDD）处理则无变化。ET显著增加硝酸盐和亚硝酸盐的生成，用PKC抑制剂预处理可使其进一步增加。PDBu可阻止ET诱导的硝酸盐/亚硝酸盐生成，而PDD则无作用。这些结果强烈表明，PKC部分介导了大鼠主动脉环中ET诱导的收缩，并且完整的内皮对于PKC抑制剂的最大抑制作用是必需的，因为ET刺激的PKC会抑制一氧化氮的释放。
