HIF-1a And HO-1 Seasonal Expression Patterns In Tissues Of Plateau Zokor(Myospalax Baileyi)

Plateau zokor (Myospalax baileyi) is one of the blind subterranean mole rats, they spend their lives solely underground in sealed burrows. In their burrows, the concentration of oxygen is low while the concentration of carbon dioxide is high, and their concentrations fluctuated extremely following the seasons.In order to study the seasonal fluctuations of the environmental factors in the burrows of plateau zokors, the temperature and humidity were measured directly by thermo-hygrometer, the water content of the soil was measured by using the drying cabinet, oxygen and carbon dioxide concentrations were measured using oxygen and carbon dioxide radiomete. Our results indicated that, in deep nests of plateau zokors, the content of oxygen was significantly lower in summer than that in spring and autumn(P <0.05), the content of carbon dioxide was significantly higher in in summer compared with that in spring and autumn(P <0.05), and there were no significant differences between spring and autumn. Compared with the seasonal fluctuations of the O₂ content in the burrows, the fluctuations of the CO₂ content was more extremely. The temperature and humidity of the soil in the burrows of plateau zokors'was steadily, there was no significant difference among the three seasons.To explore the adaptive mechanisms of the plateau zokors'blood physiological parameters to the atmospheres in their burrows, the partial pressure of the O₂ and CO₂ in the arterial blood were analyzed with blood-gas analyzer, carbon dioxide combining power (CO₂–CP) of blood plasma was analyzed by using CO₂– CP kits, red blood corpuscle and hemoglobin were analyzed with a blood indices analyzer. The results indicated that among the three seasons, the partial pressure of carbon dioxide was the highest in summer, but the partial pressure of oxygen in arterial blood increased from spring to autumn, and there were significant differences between the spring and antumn (P <0.05); the carbon dioxide combining power of blood plasma was significantly higher in summer than that in spring and antumn(P <0.05); Red blood corpuscle and hemoglobin increased from spring to autumn, there were significant differences among the three seasons (P <0.05).Through the RT-PCR and western-blotting, the seasonal expression patterns of HIF-1α(a mammalian maser regulator of O₂ homeostasis) and HO-1 at the mRNA and protein levels were measured in different tissues. The results indicated that, the expression of HIF-1αand HO-1 at mRNA and protein levels were tissue specific in plateau zokors. Among the three seasons, the mRNA and protein expression levels of HIF-1αwere highest in heart, liver, lung and kidney in summer, and showed no significant seasonal differences in muscle. But in the brain, the levels of HIF-1αmRNA decreased gradually from spring to autumn. As to the HO-1, except the muscle in which the expression of HO-1 mRNA increased gradually from spring to autumn and the lung in which the expression of HO-1 mRNA was the lowest in summer, in the others tissues including the heart, liver and kidney, the expression of HO-1 at the mRNA level was highest in summer. The expression of HO-1 at the protein level showed significant differences in different seasons, it was highest in liver and kidney in summer while it was lowest in the lung in summer, it increased gradually from spring to autumn in the heart, and it was highest in the muscle in autumn.The results indicated that the seasonal fluctuations of O₂ and CO₂ in the burrows of plateau zokors were related not only to the seasonal differences of the activities of plateau zokors, but also to the soil permeability in different seasons. The seasonal fluctustions of the O₂ and CO₂ resulted in the seasonal expression levels of the HIF-1α, and this induced the seasonal expression levels of the factors related to the O₂ transport system, because of the different structures and functions of the different organs, the expression of the HIF-1αwas tissue specific. We suggested the O₂ and CO₂ coorperated in their biological function.