الفهرس 
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Abstract
Continuous exposure to different types of stress, stress factors, pollutants and some food additives leads to physiological and biochemical disorders and may cause the incidence and progression of many diseases. Many clinical and experimental studies have indicated the role of oxidative stress as a common factor of these types of stressors in the induction of free radicals and harmful chemical reactions causing cellular damage and incidence of some diseases in humans and animals.
Previous investigations have attributed the risk of exposure to nitrate and nitrite compounds (as sodium nitrite) and their toxicity to the nitrosamide and peroxynitrite compounds. These compounds were reported to induce oxidative stress and lipid peroxidation leading to disorders of immunity, inflammation and damage of membranes and some cellular compounds. In addition, cell death and tissue damage could be induced by exposure to high dose concentrations or even to low dose concentrations over a long period of time.
On the other hand, the use of antioxidants and natural compounds, including vitamins, has attracted the attention of many recent studies to prevent the toxicity of these compounds and reduce the harmful effects, based on a balance between the rates of oxidation and antioxidants in the body. Some studies showed the importance of magnesium and pyridoxine as catalysts for many stimulating enzymes to form amino acids, lipids, carbohydrates, nucleic acids and some internal antioxidants
The aim of this study was to evaluate the oxidative stress and toxicity caused by exposure to repeated doses of sodium nitrite and to examine the effect of magnesium and pyridoxine treatment, separately or both, in the reduction and amelioration of sodium nitrite - induced oxidative stress and toxicity.
Experiments were carried out on forty male albino rats divided randomly into five equal groups as follows:
group I: was used as a control group in which rats were injected daily with 0.9% saline solution into the peritoneal cavity.
group II: Animals received daily injection of sodium nitrite (50 mg / kg) into the peritoneal cavity.
group III: Animals were injected with both sodium nitrite (50 mg / kg daily) and magnesium (150 mg / kg each alternative day) into the peritoneal cavity.
group IV: Animals were injected with both sodium nitrite (50 mg / kg daily) and Pyridoxine (300 mg / kg each alternative day) into the peritoneal cavity.
group V: Animals were injected with sodium nitrite, pyridoxine and magnesium in the same doses as in the previous groups.
After four weeks of treatment, animals were scarified and samples of blood and liver were taken. The blood samples were used to make a complete blood picture and to separate the plasma to be used to measure some biochemical parameters and evaluate the level of oxidative stress. Liver samples were used for biochemical examination, oxidation and antioxidant levels, as well as for histological examination and evaluation of pathological changes of liver tissue in different groups.
The results of this study showed the following:
1) The injection of sodium nitrite caused increase in hemoglobin concentration, red blood cells count, hematocrit value and a decrease in platelets and white blood cells count.
2) Sodium nitrite injection elevated levels of malondialdehyde (MDA) and enzymes AST, ALT, GGT, and ALP and reduced glutathione peroxidase (GPX) and glutathione (GSH) compared to the control group.
3) The microscopic examination showed a change in some cellular and histological components in the liver associated with central vein congestion, dilatation of the hepatic sinusoids, vacuolated cytoplasm, condensation of chromatin in the cell nucleus, lysis and death of certain hepatocytes.
4) Treatment with both magnesium and pyridoxine reduced levels of malondialdehyde and enzymes AST, ALT, GGT and ALP and increased levels of glutathione peroxidase (GPX) and reduced glutathione (GSH).
5) The microscopic examination of the hepatic tissue showed amelioration in the histological and cellular structure of magnesium and/or pyridoxine treated rats compared to the sodium nitrite treated rats. Cytoplasmic vacuoles, condensation of chromatin in the cell nucleus, dilatation of the hepatic sinusoids and lysis of hepatocytes were markedly reduced compared to sodium nitrite group.
It could be concluded that the exposure of the rats to the oxidative stress resulting from successive injection of sodium nitrite induced hematological and biochemical disorders in the blood and liver, associated with histopathological changes in liver, and that magnesium and pyridoxine treatment reduced these changes to varying degrees which was more obvious in the animal group treated with both of them. So, the study recommends using magnesium and pyridoxine - rich supplements for people exposed to sodium nitrite.