Abstract: To reveal the distribution and expression characteristics of the pulmonary ionocyte-related factor ATP6V0D2 in the lungs of yaks of different ages and to explore the structural formation and possible regulation of ATP6V0D2 in the yak lung for adaptation to high-altitude hypoxia. The localization and expression of ATP6V0D2 in the lungs of newborn, juvenile, adult, and elderly yaks were studied using immunohistochemistry, quantitative reverse transcription PCR (qRT-PCR), and Western blot. The results of immunohistochemistry showed that ATP6V0D2 was mainly localized in the ciliated cells and club cells of the epithelial mucosal layer of the bronchus and its branches in the lungs, and it was strongly expressed in the adult group and elderly. Expression of ATP6V0D2 in the yak lungs varied according to age. The ATP6V0D2 expression was the highest in the newborn group and was significantly different from the other three groups (P<0.05). The ATP6V0D2 protein expression of the adult group was significantly higher than the other three groups (P<0.05), and the pairwise comparisons between the newborn, juvenile, and elderly groups showed significant differences (P<0.05). ATP6V0D2 was expressed in bronchiolar epithelial cells in the lungs of yaks at different ages, and the expression levels significantly varied among different age groups(P<0.05). This study showed that ciliated cells and club cells were related to the pulmonary ionocytes in yaks. The differences in pulmonary ionocyte-related factors ATP6V0D2 was related to adaptations of yak lungs to high altitude hypoxia, through prevention of airway damage.

Key words: yak, lung, pulmonary ionocyte, ATP6V0D2