Abstract: The purpose of this study was to investigate the distribution of vessels and nerves in different parts of yaks skin, to detect the location relative expression of HIF-1α in different parts of yaks skin, and to explore the adaptation mechanism of yaks skin to the plateau hypoxia environment. The vessels and nerves in the skin of adult yaks were observed and analyzed by HE, Masson's staining and Verhoeff VG staining. The expression and distribution of HIF-1α mRNA and protein in yaks skin were studied by immunohistochemistry, real-time quantitative PCR and Western blot. The results showed that the density of vessels and nerves was the highest in the neck, followed by the forearm and crus, and the lowest in the metatarsus, there were significant differences among the parts (P<0.05). The number of vessels and nerves from the neck to the metatarsal showed a decreasing trend, with a significant difference between different sites (P<0.05). HIF-1α was mainly expressed in the epidermis, the epithelial root sheath of hair follicles, sebaceous glands, sweat glands, vessels and nerves; Strong positive expression was found in the neck, forearm and crus, and positive expression in the metatarsus (P<0.05). The relative expression level of HIF-1α mRNA in the metatarsus was significantly lower than that in the other three sites (P<0.05), but there was no significant difference in the other three sites (P>0.05). The relative expression of HIF-1α protein was the highest in the neck and the lowest in the metatarsus. The difference was significant (P<0.05). The results showed that the morphology and structure of different vessels and nerves in the skin of adult yaks were similar, and the density of vessels and nerves varied significantly from neck to forelimb to hind limb. The differential expression of HIF-1α further indicates that the skin plays a role in the adaptation of yaks to hypoxia.

Key words: yaks, skin, vessels, nerves, HIF-1α