RESUMO
The Tibetan antelope, a prototype mammal, has developed a unique adaptation to extreme high altitude-associated hypoxia. To investigate the role of the endocrine system in adaptation to high altitude in the Tibetan antelope, comparisons of endocrine hormones levels between Tibetan antelope (n = 9) and Tibetan sheep (n = 10) were performed. Both two kinds of animals were captured at an altitude of 4 300 m and then transported to experimental base at 2 800 m altitude. The blood samples were drawn from right external jugular vein in the next morning, and the 20 hormones in hypothalamus-adenohypophysis-peripheral hormonal axis were measured with radioimmunoassay or enzyme-linked immunosorbent assay. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean pulmonary arterial pressure (mPAP) were recorded using catheterization. Moreover, hemoglobin (Hb) content was measured by blood analyser. The results showed that, the levels of FT(3), FT(4) and Ang II in Tibetan antelope were significantly lower than those in Tibetan sheep, whereas TRH, CRH, GHRH, F, E(2), Ald, ACTH and CGRP levels were significantly greater in Tibetan antelope than those in the Tibetan sheep. Compared with Tibetan sheep, Tibetan antelope showed lower HR, mPAP, SBP, DBP and Hb content. In Tibetan antelope and Tibetan sheep, both Hb and Ang II were correlated positively with respective mPAP. In Tibetan antelope, FT(3) level was correlated positively with GH and negatively with ACTH. These results suggest that the endocrine system of Tibetan antelope is characterized by low energy expenditure and high stress, which may be one of the mechanisms underlying the Tibetan antelope adaptation to chronic hypoxia.