OBJECTIVETo investigate the difference of liver enzyme levels and its correlation with serum ACE/ACE2 among yak and cattle on Qinghai-Tibetan plateau, and to further explore the biochemical mechanism of their liver of altitude adaptation.

METHODSThe serum samples of yak were collected at 3,000 m, 3,500 m, 4,000 m and 4,300 m respectively, meanwhile the serum samples of migrated cattle on plateau (2,500 m) and lowland cattle (1,300 m) were also collected. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), cholinesterase (CHE), gamma glutamyl transferase (GGT), alkaline phosphatase (ALP), serum lipase (LPS), angiotensin converting enzyme(ACE), angiotensin converting enzyme-2 (ACE2) in serum were measured by using fully automatic blood biochemcal analyzer. We analysed the differences of the above enzymes and its correlation with ACE/ACE2. We used one way analysis of variance (ANOVA).

RESULTSThe levels of ALT in 4,000 m group and 4,300 m group of yak increased significantly compared with other groups, there were no statistically significant differences in AST, CHE, GGT, ACE/ACE2 levels of yaks at different altitudes. As compared to lowland cattle, the serum levels of AST and CHE were increased, the level of LPS and ACE was decreased significantly, respectively, and especially, the ratio of ACE/ACE2 of migranted cattle reduced nearly two times. The levels of LPS were significantly correlated to the ratio of ACE/ACE2 in yak (r = 0.357, P < 0.01), and a high correlation between ALP and ACE/ACE2 in lowland cattle( r = 0.418, P < 0.05), But the biggest contribution rate of the ratio of ACE/ACE2 was only 17.5% for the changes of the levels of liver enzyme.

CONCLUSIONThe results indicated that with the altitude increased did not significantly influence the changes of liver enzymes' activities in mountainous yaks but not in cattle. However, all above these changes weren't actually correlated to the ratio of ACE/ACE2.