Adaptive response of reproduction to high-altitude hypoxic stress by altering mRNA expression of hypoxia-inducible factors in female yaks (Bos grunniens).

Hypoxia-inducible factors (HIFs) are oxygen-dependent transcriptional activators, but there is little information about their role in yak (Bos grunniens) reproduction. The present study, for the first time, investigated the adaptive mechanism of yak reproduction to high-altitude hypoxic stress by comparing the expression of HIF mRNAs between female yaks at high-altitude and cattle at low-altitude. Hypothalamus, anterior pituitary, oviduct, ovary and uterus tissue samples were collected from five adult female yaks and cattle. mRNA expression was determined by the quantitative real-time polymerase chain reaction. Both HIF-1α and HIF-2α were expressed in all five tissues examined from both species, albeit at different levels. In yaks, the highest mRNA levels of HIF-1α and HIF-2α occurred in the oviduct and anterior pituitary, respectively. Both HIF-1α and HIF-2α mRNA levels were higher in yaks than in cattle (p < 0.01). These data provide evidence that adaptation of reproduction to hypoxic conditions is associated with a greater expression of HIF-1α and HIF-2α in the reproductive axis of female yaks than cattle.