Robison T W, Kim K J
Department of Molecular Pharmacology and Toxicology, University of Southern California, Los Angeles 90033, USA.
Am J Physiol. 1996 Feb;270(2 Pt 1):L266-72. doi: 10.1152/ajplung.1996.270.2.L266.
We examined the effects of nitrogen dioxide (NO2) on guinea pig tracheobronchial (GPTE) ouabain-sensitive 86Rb uptake, as an index of Na+,K(+)-ATPase activity, and specific [3H]ouabain binding. A 1-h exposure of GPTE monolayers to 5 ppm NO2 increased ouabain-sensitive 86Rb uptake (nmol.mg protein-1.30 min-1) to 512 +/- 39 compared with an air-control value of 278 +/- 20. Similarly, 1 ppm NO2 increased 86Rb uptake to 336 +/- 19 from an air control of 219 +/- 31. The specific [3H]ouabain-binding capacity (Bmax) for monolayers exposed to 5 ppm NO2 was increased to 23.2 +/- 1.2 pmol/mg protein in comparison with an air-control value of 18.4 +/- 0.4; however, there was no change at 1 ppm NO2. Binding constants (Kd) for 1 or 5 ppm NO2 were increased to 0.64 +/- 0.02 and 0.79 +/- 0.08 microM, respectively, in comparison with an air-control value of 0.53 +/- 0.02 microM. Changes of Bmax and Kd may be consistent with a recruitment of latent pumps to the basolateral cell plasma membrane and/or increased turnover of the sodium pump. However, the increase of Bmax was no more than 126% of the air control, while 86Rb uptake increased to 184%, suggesting that an increased turnover is the more predominant effect. Incubation of GPTE monolayers during NO2 exposure with nordihydroguaiaretic acid, an antioxidant, blocked the increase of ouabain-sensitive 86Rb uptake almost completely and partially protected transepithetial resistance, suggesting that lipid peroxidation processes may play a role in alterations of airway epithelial barrier and active ion transport properties.
我们研究了二氧化氮（NO₂）对豚鼠气管支气管（GPTE）哇巴因敏感的⁸⁶Rb摄取的影响，以此作为Na⁺,K⁺-ATP酶活性的指标，并研究了其对特异性[³H]哇巴因结合的影响。将GPTE单层暴露于5 ppm NO₂ 1小时后，哇巴因敏感的⁸⁶Rb摄取量（nmol·mg蛋白⁻¹·30分钟⁻¹）增加到512±39，而空气对照组的值为278±20。同样，1 ppm NO₂使⁸⁶Rb摄取量从空气对照组的219±31增加到336±19。暴露于5 ppm NO₂的单层的特异性[³H]哇巴因结合能力（Bmax）增加到23.2±1.2 pmol/mg蛋白，而空气对照组的值为18.4±0.4；然而，在1 ppm NO₂时没有变化。与空气对照组值0.53±0.02 μM相比，1或5 ppm NO₂的结合常数（Kd）分别增加到0.64±0.02和0.79±0.08 μM。Bmax和Kd的变化可能与潜在泵募集到基底外侧细胞质膜和/或钠泵周转增加一致。然而，Bmax的增加不超过空气对照组的126%，而⁸⁶Rb摄取量增加到184%，这表明周转增加是更主要的影响。在NO₂暴露期间，用抗氧化剂去甲二氢愈创木酸孵育GPTE单层，几乎完全阻断了哇巴因敏感的⁸⁶Rb摄取的增加，并部分保护了跨上皮电阻，这表明脂质过氧化过程可能在气道上皮屏障和主动离子转运特性的改变中起作用。
