Study On The Effects Of Sodium Cyanide Intoxication COX Activity Of The Rats Under Simulative High Altitude Hypoxia

China is a vast plateau region. Hypobaric hypoxia at high altitude is the main feature of the environment. Hypoxia response can lead to severe pulmonary edema, cerebral edema and other acute diseases when the troops enter high altitude area. Hydrocyanic acid is a fast-killing chemical warfare agent, which can strongly inhibit cell respiratory chain function, causing obstacles to the use of oxygen and generate energy reduction. Cyanide toxicity, mortality has been greatly improved induced by cyanide administration under the condition of plateau hypoxia. Meanwhile, treatment efficacy of the drug decreased significantly but the poisonous mechanism remains unclear. To understand the reason, we proposed that hypoxia and cyanide intoxication may lead to hypoxia animals are more sensitive to the abnormal metabolism of cyanide ion.Nitric Oxide(NO) participates in the pathological and physiological processes of vasodilatation, platelet aggregation, apoptosis and neural transmission as an important second messenger. Cytochrome oxidase is an essential hydrogen carrier in cell respiration chain. Cyanide is mainly through inhibiting the activity of cytochrome oxidase resulting in poisoning. It has been found that NO regulates the cell respiration by inhibiting the activity of cytochrome oxidase. Moreover, the effect of inhibition depends on the relative concentration between oxygen and NO. Researchers found that the cytochrome oxidase activity continued reducing in rats under the condition of decompression continuously 15days on 5000m above sea level. Our previous research has confirmed that the activity of cytochrome oxidase reduced more pronounced at 4000m high altitude hypoxia combined sodium cyanide poisoning compared with the plain poisoning, with the mechanism unknown. Therefore we suppose the NO may play an important role in regulating the activity of cytochrome oxidase. The purpose of this study is to provide a theoretical evidence for the treatment of cyanide poisoning under plateau hypoxia. In view of this, the low-pressure oxygen cabin simulated plateau environment was used to study the effects of plateau hypoxia combined NaCN intoxicatin on COX and the role of preconditioning.Results: 1.The aim of this study was to measure the blood cyanide ion concentration of rabbits and rats under the condition of plateau hypoxia for understanding its metabolism mechanism. The main toxicokinetics parameters for plain toxicant group were as follows: t_1/2 (58.174min), AUC_0～t( 126.388 mg/(L·min)), AUC(0～∞)168.566 mg/(L·min), CL/F(0.013L/min/kg), V/F(0.945L/kg) and MRT(0～t) value (46.193). For plateau group were: t_1/2 (61.116), AUC_0～t(209.554mg/L·min), AUC_{0～∞} (340.074 mg/(L·min)),CL/F(0.007L/min/kg), V/F(0.58L/kg) and MRT(0～t) value(51.142). Correlative factors of metabolism were also investigated under hypobaric hypoxia. Compared with plain NaCN intoxication group, we found that (1) hypoxia combined with NaCN intoxication induced hemoglobin concentration enhancement; (2) MHb content did not change significantly (P>0.05); (3) Urinary thiocyanate discharge was inhibited;(4) the activity of cytochrome oxidase, rhodanese and 3-MST decreased. 2. Pathologic diagnosis showed that liver and kidney injury induced by NaCN intoxication at high altitude was more serious than in plain intoxicant. 3. Compared with control group, Western blot experimental results suggested that the expression of COX I and COX IV protein markedly elevated. Meanwhile, NRF-1 protein expression decreased. 4. RT-PCR results revealed that: (1)The transcriptional level of COX I mRNA for plateau hypoxia combined NaCN intoxicant and Saponius of Panax Ginseng preconditioning group was up-regulation (P<0.05); (2) The transcriptional level of COX IV mRNA for NaCN plain intoxication group enhanced (P<0.01); (3) NRF-1 mRNA expression level decreased for all group.Furthermore,plateau hypoxia combined NaCN intoxication treated with taurine preconditioning decreased significantly(P<0.05). 5. Both plain and plateau NaCN administration produced the decrease of total NOS activity and the increase of iNOS activity of rat liver. The activity of iNOS at 308m increased more significantly than at 4000m. NO concentration of plain group reached a peak value at 1h. However, the NO concentration of plateau group increased at the time point of 30min, and then decreased. 6. Compared with plain group, chloramphenicol and L-NAME preconditioning produced the decrease of COX activity, and the former declined more significantly. 7. Taurine and Saponius of Panax Ginseng used alone or compound can be antagonistic to the decrease of COX acitivity induced by NaCN intoxication.Conclusion 1.Under the condition of plain and plateau environment, the pharmacokinetics of rabbits induced by NaCN injection was characterized by one-compartment model. Hypoxia could markedly disturb the metabolism process of NaCN in vivo. Cyanide metabolic abnormalities may be mainly account for the increase of cyanide toxicity at high altitude. 2.Light microscope and ultrastructural pathological study results suggested that pathology damage sustained increase, not easy to restore. 3. Plateau hypoxia combined NaCN intoxication can affect the COX activity, and inhibit NO production of the liver. 4. Plateau hypoxia combined NaCN intoxication resulted in up-regulation of COX I and COX IV protein expression level, and the down regulation of NRF-1 protein expression. It showed that plateau hypoxia combined NaCN intoxication promote the synthesis of COX I and COX IV protein. 5. L-NAME played a protective role on the COX activity.6. Taurine and Saponius of Panax Ginseng used alone or compound had a protective effect on the decrease of COX induced by NaCN intoxication.