Yasui Sonoko, Mawatari Kazuaki, Kawano Takashi, Morizumi Ran, Hamamoto Akiko, Furukawa Hiroko, Koyama Kei, Nakamura Aki, Hattori Atsushi, Nakano Masayuki, Harada Nagakatsu, Hosaka Toshio, Takahashi Akira, Oshita Shuzo, Nakaya Yutaka
Department of Nutrition and Metabolism, University of Tokushima Graduate School, Tokushima, Japan.
J Vasc Res. 2008;45(3):233-43. doi: 10.1159/000112545. Epub 2007 Dec 19.
The effects of insulin on the vasculature are significant because insulin resistance is associated with hypertension. To increase the understanding of the effects of insulin on the vasculature, we analyzed changes in potassium ion transport in cultured vascular smooth muscle cells (VSMCs). Using the potential-sensitive fluorescence dye bis-(1,3-dibutylbarbituric acid)trimethine oxonol [DiBAC4(3)], we found that insulin induced membrane hyperpolarization after 2 min in A10 cells. Insulin-induced hyperpolarization was suppressed by glibenclamide, an ATP-sensitive potassium (K(ATP)) channel blocker. Using a cell-attached patch clamp experiment, the K(ATP) channel was activated by insulin in both A10 cells and isolated VSMCs from rat aortas, indicating that insulin causes membrane hyperpolarization via K(ATP) channel activation. These effects were not dependent on intracellular ATP concentration, but wortmannin, a phosphatidylinositol 3-kinase (PI3-K) inhibitor, significantly suppressed insulin-induced K(ATP) channel activation. In addition, insulin enhanced phosphorylation of insulin receptor, insulin receptor substrate (IRS)-1 and protein kinase B (Akt) after 2 min. These data suggest that K(ATP) channel activation by insulin is mediated by PI3-K. Furthermore, using a nitric oxide synthase (NOS) inhibitor, we found that NOS might play an important role downstream of PI3-K in insulin-induced K(ATP) channel activation. This study may contribute to our understanding of mechanisms of insulin resistance-associated hypertension.
胰岛素对血管系统的影响意义重大，因为胰岛素抵抗与高血压相关。为了增进对胰岛素对血管系统影响的理解，我们分析了培养的血管平滑肌细胞（VSMC）中钾离子转运的变化。使用电位敏感荧光染料双（1,3 - 二丁基巴比妥酸）三甲川草酚菁[DiBAC4(3)]，我们发现胰岛素在A10细胞中2分钟后诱导细胞膜超极化。胰岛素诱导的超极化被格列本脲（一种ATP敏感性钾（K(ATP)）通道阻滞剂）抑制。通过细胞贴附式膜片钳实验，在A10细胞和从大鼠主动脉分离的VSMC中，K(ATP)通道均被胰岛素激活，表明胰岛素通过激活K(ATP)通道导致细胞膜超极化。这些效应不依赖于细胞内ATP浓度，但渥曼青霉素（一种磷脂酰肌醇3 - 激酶（PI3 - K）抑制剂）显著抑制胰岛素诱导的K(ATP)通道激活。此外，胰岛素在2分钟后增强了胰岛素受体、胰岛素受体底物（IRS）-1和蛋白激酶B（Akt）的磷酸化。这些数据表明胰岛素激活K(ATP)通道是由PI3 - K介导的。此外，使用一氧化氮合酶（NOS）抑制剂，我们发现NOS可能在PI3 - K下游在胰岛素诱导的K(ATP)通道激活中起重要作用。这项研究可能有助于我们理解胰岛素抵抗相关高血压的机制。
