The Inhibitory Effects Of Hypoxia On Mitochondrial Respiratory Chain Complexand Correlative Expression Of The Active Substances In Gastrointestinal Tissue Of Rats

The human body can produce each multi compensatory response by the exposure to high altitude hypoxia. Mitochondria is a important structures at the site of cellular respiration and oxidative phosphorylation and plays an important role in maintaining normal cell energy metabolism, ion transport and other functions, and is also more sensitive to ischemia and hypoxia. The hypoxia by simulated 5000 m altitude can cause central or peripheral adjustment factor changes, gastrointestinal mucosal barrier damage and affect to some degree in digestion, absorption, secretion, and other functions. Hypoxia can cause changes related to the active substances, disorder in imbalance of mitochondrial oxidative stress at gastrointestinal tissue, result in a series of compensatory changes in sexual function. Therefore, the work has important significance for the study of hypoxic response and adaptation mechanisms.The healthy male Wister rats were used as materials, the hypoxia simulation was used 5000 m altitude with a low-pressure chamber, hypoxic exposure group was divided into 4h, 24 h, 72 h groups(n=7). Animals were placed in hypoxic cabin and control was set as normoxic environment at Lanzhou(altitude 1500 m). After hypoxia-treatments, animals were removed, killed, and serum, stomach and small intestine were separated for mitochondria extraction. The activity of mitochondrial respiratory chain enzyme complexes Ⅰ(C Ⅰ, NADH dehydrogenase), Ⅱ(C Ⅱ,succinate dehydrogenase), Ⅲ(CⅢ, cytochrome C reductase), Ⅳ(CⅣ, cytochrome C oxidase) was tested by spectrophotometry for the different hypoxia exposure in the stomach and small intestine tissue, and the activity of superoxide dismutase(SOD)and the content of lipid peroxidation product malondialdehyde(MDA) was also determined respectively. The expression of hypoxia inducible factor-1α(HIF-1α), Bax protein, Bcl-2 protein, tumor necrosis factor-α(TNF-α) and c-fos protein in tissues was detected using immunohistochemistry. The activity of serum SOD and MDA was tested at last.Results1. After 4h simulated 5000 m altitude hypoxia, the activity of mitochondrialrespiratory chain enzyme complexes CⅠ, CⅡ, CⅢ and CⅣ in rat stomach and small intestine was significantly lower(P<0.05 or P<0.01), CⅣ activity at gastric tissue was 59.95 % as that of controls and was reduced most significantly, and CⅠactivity of intestinal tissue reduced most notable for 63.29% of the control group. 24 h hypoxia, complex activity trend recovery gradually, while it was lower than that of control group(P<0.01 or P<0.05) and higher than that of 4h treatment group(P<0.01 or P<0.05). 72 h hypoxia, it had no significant difference(P>0.05) compared with control. Acute hypoxia induced a decrease of activity of mitochondrial respiratory chain complex at gastric and intestinal tissue, could cause a decrease in cell metabolism, but metabolism tends to rise at subacute hyoxia.2. After Hypoxia treatment 4h, 24 h and 72 h, SOD activity mitochondrial complex at the stomach and small intestine tissue was significantly decreased(P<0.05 or P<0.01). MDA content at mitochondria in the gastrointestinal tissue were higher than that of control(P<0.05 or P<0.01) in hypoxia group and the most significant increase(P<0.01) at hypoxic 24 h. Serum SOD activity was significantly lower(P<0.01) and decreased most significantly at hypoxic 24h(P<0.01). MDA content in0-72 h hypoxia group were higher than that of control(P<0.05 or P<0.01). The changes of free radicals by hypoxia might cause a negative effect to cell metabolism.3. After Hypoxia treatment 4h, at intestinal tissue of rat, HIF-1α, Bax expression was higher(P<0.01), while Bcl-2 than the control group(P<0.01), after 24 h HIF-1αexpression group is 3.8 times(P<0.01) that than control group, Bax expression is 2.15 times of the control group(P<0.01), Bcl-2 than the control group was 70.56%controls(P<0.01), Bcl-2/Bax the value is also reduced to a minimum. Hypoxia 72 h HIF-1α, Bax expression lower than the 24 h have different degrees(P<0.01), whereas the expression of Bcl-2 is higher than the 24 h group(P<0.05). 24 h response to hypoxia HIF-1α expression important time, increased hypoxia inducible response and adaptation mechanisms of the body, and its expression was positively correlated with Bax, and Bcl-2 expression was negatively correlated, suggesting that it may be involved in promoting cell apoptotic response.4. 4h hypoxia, TNF-α positive expression at rat intestinal tissue was significantlyhigher(P<0.01) as 1.95 times compared with control. c-fos expression was significantly higher(P<0.01) as 2.33 times compared with control. It was lower at a certain extent at 24 h with 4h hypoxic group(P<0.01), while higher than that of control(P<0.05). The increased expression of TNF-α suggested that it was a cellular factor to acute hypoxic responses at intestinal tissue and TNF-α involved in inflammatory response in acute hypoxic stress.Conclusion1. Hypoxia induced an inhibitory effect on the activity of mitochondrial respiratory chain complex in gastric and intestinal tissue.2. Stomach, small intestine tissue and serum SOD activity was decreased significantly and MDA content and lipid oxidation products were significantly increased at hypoxic stress.3. Hypoxia induced an expression increase of HIF-1α and Bax protein in intestinal tissue while a reduction of Bcl-2 protein.4. The expression of TNF-α and c-fos was increased in varying degrees at intestinal tissue by hypoxia exposure.Simulated 5000 m hypoxia 4h was an important period for the inhibition of activity of mitochondrial respiratory chain complex and an increase of free radical mechanism and 24 h was an important period for hypoxia response of HIF-1α and apoptotic response of cells. At 72 h, hypoxia effects tend to diminish and tissue function was restored gradually.