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

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 α , 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. Copyright:

Table 1

Pulmonary morphological indicators.

Ratio	Breeds
	TGN	TJC	LYD	LJC
Lung weight / body weight	0.0085 ^a   ±  0.0010	0.0084 ^a   ±  0.0010	0.0063 ^b   ±  0.0010	0.0067 ^b   ±  0.0001
Density	0.0008 ^a   ±  0.0001	0.0008 ^a   ±  0.0001	0.0005 ^b   ±  0.0001	0.0005 ^b   ±  0.0001
Major axis / minor axis of the lung	1.8936 ^b   ±  0.0587	1.8026 ^b   ±  0.1024	2.1216 ^a   ±  0.1184	2.0077 ^ab   ±  0.1255

Note: because the Tibetan and Landrace pigs exhibited major differences in body weight, we compared the ratio of the lung weight to the body weight. Values with the same superscripts in the same row did not differ significantly ( ), and values with different superscripts in the same row differed significantly ( ).

Table 2

Diameters of the left pulmonary artery of pigs.

Part	Branches	Average diameter or weight
		TGN	LYD	TJC	LJC
		(3000 m)	(2500 m)	(1000 m)	(1000 m)
Ratio (major / minor axis)		1.3500	1.6900	1.4400	1.7500
Anterior lobe	Trunk	0.1084 ^a   ±  0.0210	0.0513 ^b   ±  0.0029	0.0914 ^a   ±  0.0165	0.0444 ^b   ±  0.0021
	First-level branch	0.0215 ^a   ±  0.0040	0.0098 ^b   ±  0.0005	0.0175 ^a   ±  0.0026	0.0085 ^b   ±  0.0003
	Second-level branch	0.0102 ^a   ±  0.0020	0.0048 ^b   ±  0.0003	0.0086 ^a   ±  0.0016	0.0042 ^b   ±  0.0002
	Third-level branch	0.0088 ^a   ±  0.0003	0.0025 ^b   ±  0.0001	0.0085 ^a   ±  0.0004	0.0023 ^b   ±  0.0001
	Fourth-level branch	0.0058 ^a   ±  0.0004	0.0014 ^b   ±  0.0002	0.0061 ^a   ±  0.0008	0.0014 ^b   ±  0.0001
Middle lobe	Trunk	0.0621 ^a   ±  0.0121	0.0294 ^b   ±  0.0016	0.0508 ^a   ±  0.0103	0.0254 ^b   ±  0.0012
	First-level branch	0.0092 ^a   ±  0.0019	0.0043 ^b   ±  0.0003	0.0077 ^a   ±  0.0014	0.0036 ^b   ±  0.0003
	Second-level branch	0.0081 ^a   ±  0.0007	0.0021 ^b   ±  0.0001	0.0082 ^a   ±  0.0006	0.0022 ^b   ±  0.0003
	Third-level branch	0.0035 ^a   ±  0.0007	0.0017 ^b   ±  0.0001	0.0030 ^a   ±  0.0005	0.0014 ^b   ±  0.0001
	Fourth-level branch	0.0027 ^a   ±  0.0006	0.0010 ^b   ±  0.0000	0.0028 ^a   ±  0.0003	0.0007 ^b   ±  0.0000
Rear lobe	Trunk	0.0248 ^a   ±  0.0048	0.0120 ^b   ±  0.0009	0.0209 ^a   ±  0.0038	0.0107 ^b   ±  0.0018
	First-level branch	0.0198 ^a   ±  0.0038	0.0092 ^b   ±  0.0005	0.0165 ^a   ±  0.0021	0.0035 ^b   ±  0.0001
	Second-level branch	0.0098 ^a   ±  0.0014	0.0041 ^b   ±  0.0001	0.0087 ^a   ±  0.0010	0.0065 ^b   ±  0.0001
	Third-level branch	0.0070 ^a   ±  0.0003	0.0022 ^b   ±  0.0000	0.0067 ^a   ±  0.0003	0.0020 ^b   ±  0.0000
	Fourth-level branch	0.0042 ^a   ±  0.0004	0.0012 ^b   ±  0.0001	0.0047 ^a   ±  0.0004	0.0011 ^b   ±  0.0001

Notes: values with the same superscripts in the same row did not significantly differ ( ), and values with different superscripts in the same row differed significantly ( ).

Table 3

Blood physiological indexes of the pigs.

Index	Unit	Breeds
		TGN	LYD	TJC	LJC
		(3000 m)	(2500 m)	(1000 m)	(1000 m)
RBC	× 10 ^12 /L	7.25 ^ab   ±  0.74	7.94 ^a   ±  0.27	6.34 ^b   ±  0.81	7.23 ^ab   ±  0.55
HGB	g/L	148.33 ^a   ±  3.46	152.00 ^a   ±  5.03	112.67 ^c   ±  5.51	128.00 ^b   ±  5.00
HCT	%	53.37 ^a   ±  3.73	48.13 ^b   ±  1.22	37.27 ^c   ±  1.57	45.80 ^b   ±  2.08
MCV	fL	73.77 ^a   ±  4.21	60.63 ^b   ±  1.76	59.20 ^b   ±  5.47	63.47 ^b   ±  3.43
MCH	pg	20.57 ^a   ±  1.14	18.70 ^ab   ±  0.66	17.93 ^b   ±  1.64	18.63 ^ab   ±  0.61
MCHC	g/L	302.67 ^ab   ±  4.04	308.33 ^a   ±  2.52	279.00 ^c   ±  5.29	294.00 ^b   ±  6.08
RDW-CV	%	18.03 ^a   ±  0.70	16.60 ^ab   ±  0.8	16.20 ^b   ±  0.44	16.70 ^ab   ±  1.25
RDW-SD	fL	55.60 ^a   ±  3.10	41.93 ^b   ±  1.89	40.07 ^b   ±  2.73	44.27 ^b   ±  3.33
Hb ^*	g/L	14.73 ^a   ±  0.23	14.67 ^a   ±  0.40	12.10 ^c   ±  0.44	13.27 ^b   ±  0.58

Notes: values with the same superscripts in the same row did not differ significantly ( ), and values with different superscripts in the same row differed significantly ( ).