Characteristics of Tibetan pig lung tissue in response to a hypoxic environment on the Qinghai-Tibet Plateau

Abstract

To adapt to the plateau environment, Tibetan pigs' lungs have developed a unique physiological mechanism during evolution. The vascular corrosion casting technique and scanning electron microscopy were used to understand arterial architecture. Blood physiological index and quantitative real-time PCR (qRT-PCR) were used for assessing whether the lung can regulate the body through anatomical, physiological and molecular mechanisms to adapt to hypoxic environments. Our study showed that the lungs of Tibetan pigs were heavier and wider and that the pulmonary arteries were thicker and branched and had a denser vascular network than those of Landrace pigs. The hemoglobin (HGB), mean corpuscular hemoglobin concentration (MCHC) values of high-altitude pigs were significantly higher than those of low-altitude pigs. The expression levels of HIF- 1 $\alpha$ , EPAS1, EPO and VEGF, but not those of eNOSand EGLN1, were significantly higher in the lungs of high-altitude pigs than in those from pigs at a lower altitude ( $P<0.05$ ). These findings and a comprehensive analysis help elucidate the pulmonary mechanism of hypoxic adaptation in pigs.

Figure 1

The lungs of Tibetan pigs (right) and Landrace pigs (left). A: left lung; B: right lung; a: left anterior lobe; b: left middle lobe; c: left rear lobe; d: right anterior lobe; e: right middle lobe; f: right rear lobe.

Figure 2

Morphological features of the pulmonary artery. Tibetan pig cast specimens of the pulmonary artery are on the left, and Landrace pig cast specimens of the pulmonary artery are on the right.

Figure 3

Distribution and superficial features of the arterioles in the left lung. (a) The arteriole distribution of the LYD group ( $\times$ 30). (b) The arteriole distribution of the TGN group ( $\times$ 20). (c) The arteriole distribution of the TJC group ( $\times$ 30). (d) The arteriole distribution of the LJC group ( $\times$ 30). (e) Microvascular terminal, with a triangle mark ( $\times$ 70). (f) Imprints of the endothelial nuclei of the LYD group ( $\times$ 200). (g) Imprints of the endothelial nuclei of the TGN group ( $\times$ 200). (h) Imprints of the endothelial nuclei of the TJC group ( $\times$ 300). (i) Imprints of the endothelial nuclei of the LJC group ( $\times$ 200). (j) Precapillary arterioles ( $\times$ 700).

Figure 4

Expression levels of HIF- 1 $\mathit{\alpha }$ , EPAS1, EPO, VEGF, eNOS and EGLN1 in the lungs of the four types of pigs and the relationship between VEGF, EPO and EGLN1 and diameter, RBCs and HGB. Note: the different letters above the bars indicate that the expression levels differed significantly ( $P\mathit{<}\mathrm{0.05}$ , mean  $\pm$  SE), and the same letters indicate that the levels did not differ significantly ( $P\mathit{>}\mathrm{0.05}$ , mean  $\pm$  SE) in different breeds.