Davda R K, Chandler L J, Guzman N J
Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville.
Eur J Pharmacol. 1994 Feb 15;266(3):237-44. doi: 10.1016/0922-4106(94)90132-5.
The intracellular regulation of nitric oxide synthase has been the focus of intense investigation. Bioassay studies using vascular rings have suggested that protein kinase C inhibits endothelium-dependent vascular relaxation. However, information regarding the effects of protein kinase C on the synthesis of nitric oxide in endothelial cells is not available. Therefore, we investigated the effects of protein kinase C to regulate receptor-independent activation of nitric oxide synthase activity in cultured bovine pulmonary artery endothelial cells. Activation of protein kinase C by phorbol 12-myristate 13-acetate or 1,2-dioctanoyl-sn-glycerol inhibited receptor-dependent and receptor-independent nitric oxide synthase activity. The inhibition of nitric oxide synthase by protein kinase C was concentration dependent and markedly blunted by staurosporine. The inhibition of protein kinase C by staurosporine alone enhanced basal nitric oxide synthase activity. Furthermore, depletion of protein kinase C enhanced both basal and agonist-stimulated nitric oxide synthase activity. These studies indicate that protein kinase C modulates the activity of the constitutive Ca2+/calmodulin-dependent endothelial nitric oxide synthase in the basal state and following agonist stimulation through direct inhibition of the enzyme as well as receptor desensitization. These direct regulatory effects of protein kinase C on endothelial nitric oxide synthase activity may have important implications in the physiologic regulation of vascular tone.
一氧化氮合酶的细胞内调节一直是深入研究的焦点。使用血管环进行的生物测定研究表明，蛋白激酶C抑制内皮依赖性血管舒张。然而，关于蛋白激酶C对内皮细胞中一氧化氮合成影响的信息尚不可得。因此，我们研究了蛋白激酶C对培养的牛肺动脉内皮细胞中一氧化氮合酶活性的受体非依赖性激活的调节作用。佛波醇12-肉豆蔻酸酯13-乙酸酯或1,2-二辛酰基-sn-甘油激活蛋白激酶C可抑制受体依赖性和受体非依赖性一氧化氮合酶活性。蛋白激酶C对一氧化氮合酶的抑制作用呈浓度依赖性，并且被星形孢菌素显著减弱。单独使用星形孢菌素抑制蛋白激酶C可增强基础一氧化氮合酶活性。此外，蛋白激酶C的耗竭增强了基础和激动剂刺激的一氧化氮合酶活性。这些研究表明，蛋白激酶C在基础状态和激动剂刺激后通过直接抑制该酶以及受体脱敏来调节组成型Ca2+/钙调蛋白依赖性内皮一氧化氮合酶的活性。蛋白激酶C对内皮一氧化氮合酶活性的这些直接调节作用可能在血管张力的生理调节中具有重要意义。
