The kinetic differences between sodium nitrite, amyl nitrite and nitroglycerin oxidation of hemoglobin

The effect of sodium nitrite, amyl nitrite and nitroglycerin (glyceryl trinitrate) on the hemoglobin of adult erythrocytes was examined in vitro. Both amyl nitrite and nitroglycerin reacted immediately with oxyhemoglobin to effect oxidation into methemoglobin while sodium nitrite required an inductionary period (lag phase) prior to the reaction. Kinetic studies of the biomolecular rate law for each of the preceding reaction's reactionary periods (log phases) allowed rate constant calculations to be made. The values are 1.14 x 10(4) M-1 min-1, 7.45 x 10(4) M-1 min-1, and 3.50 x 10(1) M-1 min-1 for sodium nitrite, amyl nitrite and nitroglycerin, respectively. A comparison of the amyl nitrite and nitroglycerin rate constants reveals that amyl nitrite is approximately 2000-fold more toxic to oxyhemoglobin than nitroglycerin. These oxidant's effect on in vitro hemoglobin solutions are comparable since both reactions approximate to rectangular hyperbolae. Sodium nitrite reacts about 300-fold faster with oxyhemoglobin than does nitroglycerin. However, the sodium nitrite reaction proceeds in a sigmoidal fashion which makes a strict comparison between these compounds relative toxicities less clear cut.     

Mutagenic effect of sodium nitrite on cultured mouse cells

Effect of sodium nitrite on cultured FM3A cells, a C3H mouse mammary carcinoma cell line, was examined. The chromosomal preparations demonstrated that severe aberrations were induced in more than 80% of the mitotic plates at 10⁻² M and in nearly 40% at 10^−2.5 M after 24 and 48 h treatment. According to the results of alkaline sucrose gradient analysis sedimentation profiles of cell DNA treated at as high as 10⁻¹ M for 24 h scarcely changed from that of control cell DNA. Induction of 8-azaguanine-resistant mutation was demonstrated above 10⁻³ M sodium nitrite.     

The effect of sodium nitrite on the growth of Micrococcus denitrificans

Summary Nitrite accumulates during the growth of M. denitrificans in a medium in which nitrate is the terminal oxidant. If H₂ is the electron donor for nitrate reduction, the level of nitrite produced is sufficiently high to inhibit hydrogenase; this inhibition consequently inhibits growth. Yeast extract alleviates the inhibition and permits a resumption of growth. The release from inhibition may result from the provision of a growth factor for or from a more rapid induction of, a system for nitrite dissimilation.Dedicated to Prof. C. B. van Niel on the occasion of his 70th birthday. The author is indepted to Prof. Van Niel for many helpful suggestions and discussions, and for the hospitality of his laboratory during the author's stay as a National Science Foundation Post-Doctoral Fellow.     

Combined effect of propofol and GSNO on oxidative phosphorylation of isolated rat liver mitochondria.

Isolated rat liver mitochondria have been treated with the general anaesthetic propofol (2,6-diisopropylphenol, 200 microM) and the physiological NO donor nitrosoglutathione (GSNO, 200 or 250 microM). The efficiency of the oxidative phosphorylation has been evaluated by measuring the respiration and ATP synthesis rates and the behavior of transmembrane electrical potential. In mitochondria energized by succinate, the simultaneous presence of both propofol and GSNO gives rise to a synergic action in affecting the resting and the ADP-stimulated respiration, the respiratory control ratio, the ATP synthesis, and the formation and utilization of the electrochemical transmembrane potential.     

Combined hypoxia and sodium nitrite pretreatment for cardiomyocyte protection in vitro

Methods that increase cardiomyocyte survival upon exposure to ischemia, hypoxia and reoxygenation injuries are required to improve the efficacy of cardiac cell therapy and enhance the viability and function of engineered tissues. We investigated the effect of combined hypoxia/NaNO₂ pretreatment on rat neonatal cardiomyocyte (CM), cardiac fibroblast, and human embryonic stem cell‐derived CM (hESC‐CM) survival upon exposure to hypoxia/reoxygenation (H/R) injury in vitro. Cells were pretreated with and without hypoxia and/or various concentrations of NaNO₂ for 20 min, then incubated for 2 h under hypoxic conditions, followed by 2 h in normoxia. The control cells were maintained under normoxia for 4 h. Pretreatment with either hypoxia or NaNO₂ significantly increased CM viability but had no effect on cardiac fibroblast viability. Combined hypoxia/NaNO₂ pretreatment significantly increased CM viability but significantly decreased cardiac fibroblast viability. In rat neonatal CMs, cell death, as determined by lactate dehydrogenase (LDH) activity, was significantly reduced with hypoxia/NaNO₂ pretreatment; and in hESC‐CMs, hypoxia/NaNO₂ pretreatment increased the BCL‐2/BAX gene expression ratio, suggesting that hypoxia/NaNO₂ pretreatment promotes cell viability by downregulating apoptosis. Additionally, we found a correlation between the prosurvival effect of hypoxia/NaNO₂ pretreatment and the myoglobin content of the cells by comparing neonatal rat ventricular and atrial CMs, which express high and low myoglobin respectively. Functionally, hypoxia/NaNO₂ pretreatment significantly improved the excitation threshold upon H/R injury to the level observed for uninjured cells, whereas pretreatment did not affect the maximum capture rate. Hence, hypoxia/NaNO₂ pretreatment may serve as a strategy to increase CM survival in cardiac regenerative therapy applications and tissue engineering. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:482–492, 2015     

Inhibitors of the nitrite oxidation of hemoglobin

Different types of active inhibitors of the reaction of nitrite hemoglobin oxidation have been revealed and studied. The dependence of inhibition of methemoglobin formation, on concentration of inhibitors at pH 5.9 and 7.17 has been determined. Differential absorption spectra of the inhibitors in the presence sodium nitrite in UV and visual light has been studied. The values of oxidation-reduction potentials have been estimated. Possible mechanism of action of the inhibitors has been discussed.     

Effect of sodium nitrite on the alpha-chlorohydrin-induced lesion of the testis--epididymis complexin the rat.

Administration of vasodilator, sodium nitrite (20 mg/kg body weight), 30 min before alpha-chlorohydrin treatment (90 mg/kg body weight) prevented the chlorohydrin-induced lesion in rat testis--epididymis complex. However, administration of vasodilator 90 min after alpha-chlorohydrin treatment did not prevent the chlorohydrin-induced lesion in the testis--epididymis complex. These observations suggest that the testicular vasculature is involved in drug action.     

The effect of gamma-irradiation on the level of circulating immune complexes in rat blood

During the first 10-20 min after gamma-irradiation (75 Gy) of rat head in the cranio-caudal direction a drastic 2-3-fold decrease was observed in the level of circulating immune complexes (CIC) in the blood. CIC content of the blood was restored 60 min after irradiation, and no changes occurred during the following 5-hour period of observation.     

Insulin sensitivity of rat muscle sodium pump

The aim of the present study was to examine the possible physiological responsiveness of the sodium pump to insulin in rat muscle, an effect that has never been convincingly demonstrated. The insulin stimulation of the sodium pump was estimated by two well-established parameters: ouabain binding to pieces of soleus muscle, and Na/K-ATPase activity of purified plasma membranes. For both parameters the dose dependence of the insulin effect on the sodium pump shows the characteristic bell-shaped stimulation pattern, with a maximum in the physiological hormone concentration range. This result has not been observed in previous studies where insulin concentrations two to three orders of magnitude higher were used. It can be concluded that an effect of insulin on the regulation of the Na pump in muscle might well be operating in vivo.     

Combined effect of HEDTA and selenium against aluminum induced oxidative stress in rat brain

Aluminium (Al) is a potent neurotoxin and has together with other metals been suggested to be associated with Alzheimer's disease causality. The current study was carried out to investigate the potential role of N(2-hydroxyethyl) ethylenediamine triacetic acid (HEDTA) and Se in combination against Al induced toxicity. Animals were exposed to Al at a dose of 27 mg/kg/d i.p. for 60 days. HEDTA and Se were administered at a dose of 20mg/kg/d i.p. and 0.5mg/kg/d orally, respectively for 7 consecutive days. Induction of oxidative stress was recorded in the brain after Al exposure. Significant decrease was found in the levels of reduced glutathione activities of the enzymes glutathione reductase, glutathione peroxidase, catalase, superoxide dismutase, acetyl cholinesterase, and increased levels were observed in LPO and glutathione-S-transferase activity in brain and serum. These parameters responded positively to therapy with HEDTA, but more pronounced beneficial effects were observed when HEDTA was administered in combination with Se. The combination was effective in reducing the concentration of Al and level of DNA damage.     

Combined treatment of preimplantation mouse embryos in vitro with sodium nitrite and X-rays

Summary Man takes up nitrite in a considerable amount. Effects of nitrite on DNA have been reported; therefore, interaction between nitrite and radiation might be possible.Preimplantation mouse embryos in vitro were treated with a combination of sodium nitrite (1 mM or 2.5 mM) and X-rays (0.94 Gy) in order to obtain some information whether radiation risk is influenced by the presence of nitrite. The microscopic visible development up to 144 h post conceptionem (h p.c.), the number of cell nuclei, and the number of micronuclei were determined.None of the experimental results gives any indication that radiation risk is influenced by nitrite. All effects after combined treatment correspond to the sum of the single effects.     

The effect of external gamma-irradiation on the distribution of deuterium oxide in the rat body

External gamma-irradiation (7.74 and 15.48 x 10(-2) C/kg) does not influence the distribution of deuterium oxide within a rat body: it is distributed uniformly among the organs and tissues as it is observed in nonirradiated animals. The effect of external irradiation favors the retention of deuterium oxide within the organs and tissues. The delayed excretion of deuterium oxide from the body can enhance the biological effect. This should be taken into account in standardizing the combined radiation effects.     

Analysis of responses to glyceryl trinitrate and sodium nitrite in the intact chest rat

Responses to glyceryl trinitrate/nitroglycerin (GTN), S-nitrosoglutathione (GSNO), and sodium nitrite were compared in the intact chest rat. The iv injections of GTN, sodium nitrite, and GSNO produced dose-dependent decreases in pulmonary and systemic arterial pressures. In as much as cardiac output was not reduced, the decreases in pulmonary and systemic arterial pressures indicate that GTN, sodium nitrite, and GSNO have significant vasodilator activity in the pulmonary and systemic vascular beds in the rat. Responses to GTN were attenuated by cyanamide, but not allopurinol, whereas responses to nitrite formed by the metabolism of GTN were attenuated by allopurinol and cyanamide. The results with allopurinol and cyanamide suggest that only mitochondrial aldehyde dehydrogenase is involved in the bioactivation of GTN, sodium nitrite, and GSNO, whereas both pathways are involved in the bioactivation of nitrite anion in the intact rat. The comparison of vasodilator activity indicates that GSNO and GTN are more than 1000-fold more potent than sodium nitrite in decreasing pulmonary and systemic arterial pressures in the rat. Following administration of 1H-[1,2,4]-oxadizaolo[4,3-]quinoxaline-1-one (ODQ), responses to GTN were significantly attenuated, indicating that responses are mediated by the activation of soluble guanylyl cyclase. These data suggest that the reduction of nitrite to nitric oxide formed from the metabolism of GTN, cannot account for the vasodilator activity of GTN in the intact rat and that another mechanism; perhaps the formation of an S-NO, may mediate the vasodilator response to GTN in this species.     

Possible involvement of NO-mediated oxidative stress in induction of rat forestomach damage and cell proliferation by combined treatment with catechol and sodium nitrite

To clarify the mechanisms underlying forestomach carcinogenesis in rats by co-treatment with catechol and sodium nitrite (NaNO2), we investigated the involvement of oxidative stress resulting from reaction of the two compounds. Since generation of semiquinone radical, hydroxyl radical (*OH), and peroxynitrite (ONOO-) arose through the reaction of catechol with NO, we proposed that superoxide resulting from catechol oxidation reacted with excess NO, consequently yielding *OH via ONOO-. Male F344 rats were co-treated with 0.2% catechol in the diet and 0.8% NaNO2 in the drinking water for 2 weeks. Prior to occurrence of histological evidence indicating epithelial injury and hyperplasia, 8-hydroxydeoxyguanosine levels in forestomach epithelium significantly increased from 12 h together with appearance of immunohistochemically nitrotyrosine-positive epithelial cells. There were no remarkable changes in rats given each chemical alone. We conclude that oxidative stress due to NO plays an important role in induction of forestomach epithelial damage, cell proliferation, and thus presumably forestomach carcinogenesis.