Coppock E A, Tamkun M M
Department of Physiology, Colorado State University, Fort Collins, Colorado 80523, USA.
Am J Physiol Lung Cell Mol Physiol. 2001 Dec;281(6):L1350-60. doi: 10.1152/ajplung.2001.281.6.L1350.
Resistance pulmonary arteries constrict in response to hypoxia, whereas conduit pulmonary arteries typically do not respond or dilate slightly. One proposed mechanism for this differential response is the variable expression of pulmonary arterial smooth muscle cell voltage-gated K(+) (K(V)) channel subunits (Kv1.2, Kv2.1, Kv1.5, and Kv3.1b) shown to be O(2) sensitive in heterologous expression systems. In this study, immunoblotting and immunohistochemistry were used to examine the expression of K(V) channel alpha- and beta-subunits in the bovine pulmonary arterial circulation to determine whether differential K(V) channel subunit distribution is responsible for the distinct sensitivities of pulmonary arteries to hypoxia. Surprisingly, there was little difference in the expression levels of Kv1.2, Kv1.5, and Kv2.1 between conduit and resistance pulmonary arteries. In contrast, expression of the Kv3.1b alpha-subunit and Kv beta.1, Kv beta 1.2, and Kv beta 1.3 accessory subunits dramatically increased along the pulmonary arterial tree. The differential expression of all the beta-subunits but of only one of the putative O(2)-sensitive alpha-subunits suggests that the alpha-subunits alone are not the O(2) sensors but further implicates the auxiliary beta-subunits in pulmonary arterial O(2) sensing.
阻力性肺动脉会对低氧作出收缩反应，而传导性肺动脉通常无反应或仅有轻微扩张。对于这种差异反应，一种提出的机制是肺动脉平滑肌细胞电压门控钾离子（K(+)）通道亚基（Kv1.2、Kv2.1、Kv1.5和Kv3.1b）的表达存在差异，这些亚基在异源表达系统中显示对氧气敏感。在本研究中，采用免疫印迹和免疫组织化学方法检测牛肺动脉循环中K(V)通道α亚基和β亚基的表达，以确定K(V)通道亚基的差异分布是否导致肺动脉对低氧的不同敏感性。令人惊讶的是，传导性肺动脉和阻力性肺动脉之间Kv1.2、Kv1.5和Kv2.1的表达水平几乎没有差异。相比之下，Kv3.1bα亚基以及Kvβ.1、Kvβ1.2和Kvβ1.3辅助亚基的表达沿肺动脉树显著增加。所有β亚基的差异表达，但只有一个假定的对氧气敏感的α亚基存在差异，这表明仅α亚基不是氧气传感器，而是进一步暗示辅助β亚基参与了肺动脉的氧气感知。
