Fiscus R R, Rapoport R M, Murad F
J Cyclic Nucleotide Protein Phosphor Res. 1983;9(6):415-25.
Cyclic GMP-dependent protein kinase (cyclic GMP-kinase) activity in isolated strips of rat aorta was measured in the absence and presence of exogenous cyclic GMP (2 microM) and expressed as a ratio. This activity ratio represented an estimate of the endogenous activation state of the enzyme. Acetylcholine [10 microM), an endothelium-dependent vasodilator, increased the activity ratio from a control value of 0.42 to 0.71 in aorta with endothelium intact. With endothelium removed, acetylcholine had no effect on cyclic GMP-kinase activity. The nitrovasodilator sodium nitroprusside (50 nM) increased activity ratios in aorta both with (0.42 to 0.54) and without (0.29 to 0.40) endothelium. Since activity ratios were higher in aortas with an intact endothelium, a tonic influence of the endothelium on aorta cyclic GMP-kinase is suggested. The vasodilator isoproterenol (3 microM) had no effect on cyclic GMP-kinase activity ratios. The increases in cyclic GMP-kinase activity caused by sodium nitroprusside and acetylcholine were preserved when aortas were homogenized in buffer containing 3 mg/ml charcoal. Thus, most of the cyclic GMP-kinase activation occurred in the intact tissue and not because of endogenous cyclic nucleotides present during homogenization or assay. The increases in the activity ratio to sodium nitroprusside and acetylcholine correlate with increases in cyclic GMP concentration and with smooth muscle relaxation. It is concluded that cyclic GMP-kinase in rat aorta is activated by acetylcholine in an endothelium-dependent manner and by sodium nitroprusside in an endothelium-independent manner. These data are consistent with the hypothesis that cyclic GMP mediates relaxation of vascular smooth muscle to acetylcholine and sodium nitroprusside by activating cyclic GMP-kinase and consequent protein phosphorylation. The data further illustrate the importance of endothelial cells in vascular responses to acetylcholine.
在有无外源性环鸟苷酸（2微摩尔）的情况下，测定了离体大鼠主动脉条中的环鸟苷酸依赖性蛋白激酶（环鸟苷酸激酶）活性，并将其表示为一个比值。该活性比值代表了该酶内源性激活状态的一种估计。乙酰胆碱[10微摩尔]，一种内皮依赖性血管舒张剂，在完整内皮的主动脉中使活性比值从对照值0.42增加到0.71。去除内皮后，乙酰胆碱对环鸟苷酸激酶活性无影响。硝基血管舒张剂硝普钠（50纳摩尔）在有（0.42至0.54）和无（0.29至0.40）内皮的主动脉中均增加了活性比值。由于完整内皮的主动脉中活性比值更高，提示内皮对主动脉环鸟苷酸激酶有紧张性影响。血管舒张剂异丙肾上腺素（3微摩尔）对环鸟苷酸激酶活性比值无影响。当主动脉在含有3毫克/毫升活性炭的缓冲液中匀浆时，硝普钠和乙酰胆碱引起的环鸟苷酸激酶活性增加得以保留。因此，大多数环鸟苷酸激酶的激活发生在完整组织中，而非由于匀浆或测定过程中存在的内源性环核苷酸。对硝普钠和乙酰胆碱的活性比值增加与环鸟苷酸浓度增加及平滑肌舒张相关。结论是，大鼠主动脉中的环鸟苷酸激酶以内皮依赖性方式被乙酰胆碱激活，以内皮非依赖性方式被硝普钠激活。这些数据与环鸟苷酸通过激活环鸟苷酸激酶及随后的蛋白质磷酸化介导血管平滑肌对乙酰胆碱和硝普钠舒张作用的假说一致。这些数据进一步说明了内皮细胞在血管对乙酰胆碱反应中的重要性。
