低氧暴露下高原鼠兔肺组织间隙连接蛋白40表达分析

低氧性肺血管收缩反应钝化是高原鼠兔适应低氧环境的重要策略，但参与该生理代偿反应的功能基因尚不明确。间隙连接蛋白40 (Connexin40, Cx40) 在哺乳动物肺血管内皮表达。本研究对生活在海拔3 200 m的高原鼠兔进行28 d模拟海拔5 000 m低氧处理，以Sprague Dawley (SD) 大鼠为对照，采用免疫组化法分析模拟低氧处理后高原鼠兔和SD大鼠肺组织形态结构，qPCR和蛋白印记法检测Cx40基因和蛋白表达量变化，探究Cx40在高原鼠兔低氧性肺血管收缩反应钝化中的潜在作用。结果显示，低氧处理后，高原鼠兔肺泡呈空泡囊状，Cx40蛋白在支气管和肺血管中均表达，Cx40 基因mRNA水平随着低氧暴露而升高，但其蛋白质水平呈下降趋势，肺支气管Cx40蛋白无明显变化。SD大鼠肺血管和肺支气管表达的Cx40蛋白均无明显变化。暗示生活在高海拔低氧环境中的高原鼠兔，Cx40蛋白下调可抑制血管收缩信号，减弱低氧性肺血管收缩反应，使低氧性肺血管收缩反应钝化，以适应高原缺氧环境。研究结果可为高原土著动物适应高寒缺氧环境提供基础理论数据。

Expression analysis of gap junction protein 40 in lung of plateau pika exposed to hypoxia

Blunted hypoxic pulmonary vasoconstriction response is a major adaptation to hypoxia in plateau pika (Ochotona curzoniae). However, the genes involved in this physiological compensation remained unclear. In the present study, plateau pikas and Sprague Dawley (SD) rats were challenged with a hypoxia condition simulating an altitude of 5 000 m for 28 days. Morphological structure analysis by immunohistochemistry was carried out for the pulmonary in both species and the expression levels of Connexin40 (Cx40), a member of the Connexon family expressed in pulmonary vascular endothelia in mammals, were determined by both qPCR and Western blot. The results showed that upon hypoxia challenge the alveoli of plateau pika appeared to be vacuolated sacs. Cx40 expression was detected in both bronchi and pulmonary blood vessels in both species. In plateau pikas, mRNA level of Cx40 increased after hypoxia challenge, while its protein level decreased. In contrast, protein levels of Cx40 had no significant change with prolonged hypoxia exposure in pulmonary blood vessels of SD rats. No significant change in the Cx40 protein in the lung bronchi was observed in both species. Our results indicate that with hypoxia exposure, pulmonary vasoconstriction response in plateau pikas could be suppressed by down-regulation of Cx40, contributing to their adaptation to a hypoxic environment on the plateau. Our results can provide a reference for the expression analysis of gap junction proteins in the lungs of indigenous animals living on the Qinghai-Tibet Plateau.