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Objective To investigate effect of sodium cyanide(NaCN)at different concentrations on the mitochondrial respiratory oxygen consumption,the mitochondrial membrane potential(MMP)and activity of the complex Ⅳ of mitochondrial breath train in in vitro liver mitochondria from the rats exposed to simulated high altitude hypoxia,and to explore the characteristics of energy metabolism in the mitochondria from the rats subjected to cyanide poisoning during acute hypoxia exposure.Methods Adult Sprague-Dawley(SD)rats were set randomly into control and acute hypoxia groups(n=8 in each group).The acute hypoxic rats were exposed to simulate 5 000 m high altitude in a hypobaric chamber 23 h/d for 3 d.Rats in the control group were bred in the normoxia condition at the same time.The liver mitochondria were isolated by centrifugation.Mitochondrial oxidative respiratory consumption and activity of the complex Ⅳ was measured by Clark electrode after the treatment of NaCN at 0,0.01,0.1 and 0.25 mmol/L respectively,so as to calculate mitochondrial state 3 respiration(ST3),state 4 respiration(ST4),respiratory control rate(RCR),the rate of oxidative phosphorylation(OPR),and oxygen consumption rate of the complex Ⅳ.MMP was detected by Rhodamine 123 method at the above-mentioned concentrations of NaCN.Results NaCNat0.01,0.1and0.25mmol/Linhibited the mito-chondrial oxidative respiratory function,and decreased MMP significantly.The inhibitory effects of NaCN onenergy metabolism in mitochondria was in a dose-dependent manner.Compared with the treatment of NaCN atthe corresponding concentration in the control group,mitochondrial function in the acute hypoxia group was in-hibited more seriously.Conclusion Acute hypoxia exacerbates the inhibitory effects of sodium cyanide on en-ergy metabolism in rat liver mitochondria.Its mechanism might be relevant to the decoupling of oxidative phos-phorylation,functional down-regulation of complexⅣin respiratory chain and changes of the mitochondrialmembrane potential in liver mitochondria from rats exposed to acute hypoxia.
RESUMO
Objective To investigate effect of guanosine diphosphate (GDP) on the mitochondrial respiratory oxygen consumption and the mitochondrial membrane potential (MMP) of rat brain and explore the relationship of the change of uncoupling proteins (UCPS) activity with the oxygen consumption and MMP. Methods The mitochondria of rat brain were isolated by centrifugation. Mitochondria oxidative respiratory consumption was measured by Clark electrode after the treatment of GDP at different concentrations so as to calculate mitochondrial state 3 respiration (ST3), mitochondrial state 4 respiration (ST4), respiratory control rate (RCR), and the rate of oxidative phosphorylation (OPR). MMP was detected by Rhodamine 123 method at the different concentrations of GDP. Results With the increase of GDP concentration form 0 to 1.0 mmol/L, the values of ST3, ST4 and OPR were reduced while RCR was elevated. But when the concentration increased to 1.4 mmol/L, the former 3 indexes begun to increase while the later declined. When the GDP concentration reached to 1 mmol/L, the inhibitory rate was only 35.1%, 51.3%, 14.2% to ST3, ST4 and OPR respectively, while RCR was increased to 133.2%. No matter the concentration was over 1 mmol/L or under 1 mmol/L, the ability of inhibition was attenuated. MMP reached to the highest point when GDP exerted the highest inhibitory rate on mitochondrial respiratory oxygen consumption. Conclusion GDP, an inhibitor of UCPS, can regulate the respiratory oxygen consumption and MMP of the isolated rat brain mitochondrial directly in a dose-effect fashion. The change of UCPS activity can affect the respiratory oxygen consumption and MMP.
