Simultaneous determination of two antioxidants, uric and ascorbic acid, in animal tissue by high-performance liquid chromatography

Nephrolithiasis in free-ranging North American river otter (Lontra canadensis) in North Carolina, USA

The North American river otter (Lontra canadensis) serves as an indicator species for environmental monitoring, is prized as a valuable furbearer, and is a popular display animal in zoologic collections. Nephrolithiasis has been reported as a frequent problem in other free-ranging and captive otter species but is rarely reported in North American river otters. In this study, we compared the prevalence of nephrolithiasis diagnosed using routine gross pathologic examination techniques with the use of computed tomography (CT) of excised kidneys. We also evaluated whether otter nephroliths could be accurately classified by their CT densities, and we examined the renal tissue uric acid concentrations in free-ranging otters in North Carolina, USA. Kidneys were collected from carcasses of legally trapped, free-ranging animals. Nephroliths were observed in 16.2% of the individuals (n = 229). Associations were found between age and nephrolith status and between capture location and nephrolith status (P = 0.026 and < 0.001, respectively). Computed tomography Hounsfield unit density measurements were not useful in determining nephrolith chemical composition in this study. Renal tissue uric acid concentrations were similar across genders, age groups, and stone status. The chemical composition of the nephroliths was determined by scanning electron microscopy-energy dispersive X-ray spectroscopy to be calcium phosphate in the carbonate form.

Natural bioactive compounds of Citrus limon for food and health

Citrus genus is the most important fruit tree crop in the world and lemon is the third most important Citrus species. Several studies highlighted lemon as an important health-promoting fruit rich in phenolic compounds as well as vitamins, minerals, dietary fiber, essential oils and carotenoids. Lemon fruit has a strong commercial value for the fresh products market and food industry. Moreover, lemon productive networks generate high amounts of wastes and by-products that constitute an important source of bioactive compounds with potential for animal feed, manufactured foods, and health care. This review focuses on the phytochemistry and the analytical aspects of lemon compounds as well as on the importance for food industry and the relevance of Citrus limon for nutrition and health, bringing an overview of what is published on the bioactive compounds of this fruit.

Biomarkers of oxidative stress in Wallago attu (Bl. and Sch.) during and after a fish-kill episode at Panipat, India

The present investigation was carried out by sampling water, sediment and fish during a fish-kill episode at Panipat (Haryana, India), and again sampling at the same site was conducted after a gap of two months. During the second sampling no fish-kill was observed and the water was relatively less turbid and clear. Antioxidant profile and lipid peroxidation (LPO) in fish tissues were studied. Analysis was also carried out on the physico-chemical characteristics of water samples along with heavy metal and pesticide analysis in water and sediment samples during and after the episode. Dissolved oxygen level was substantially low during the fish-kill episode. Heavy metals (copper and chromium) and pesticides like BHC (Benzene hexachloride), DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) were also detected during the episode in water and sediment samples. Various oxidative stress biomarkers in liver, kidney and gill tissues in the Indian freshwater fish Wallago attu (Bl. and Sch.) collected from the site were investigated. The levels of reduced glutathione and non-protein thiol were significantly (P<0.001) higher in the liver of Wallago attu collected from Panipat after the fish-kill episode. Ascorbic acid levels in all the tissues did not change significantly after the episode. The LPO in liver, kidney and gills was significantly low (P<0.01-0.001) in all tissues of fish collected after the fish-kill episode. The protein carbonyl levels were significantly low (P<0.05-0.01) in all the fish organs sampled after the fish-kill episode. The findings suggest that industrial effluent may result in the massive loss of a commercial commodity. The simultaneous measurement of the physicochemical parameters of the water samples showed a good correlation between the biomarkers responses and the environmental chemical stress conditions.

Vitamin C preserves the cardio-protective paraoxonase activity of high-density lipoprotein during oxidant stress

HDL-associated paraoxonase (PON) antioxidant enzyme activity is cardio-protective. We investigated whether vitamin C prevented loss of PON activity from HDL during oxidant stress. HDL was incubated with either hydrophilic or lipophilic peroxyl radical initiators in the absence (control) or presence of vitamin C (50 and 100 micromol/L). Regardless of the type of radical, accumulation of lipid oxidation products in HDL was similar in incubations lacking vitamin C. Loss of PON activity was greater in HDL exposed to hydrophilic, in contrast to lipophilic, radicals, but addition of vitamin C maintained enzyme activity. Vitamin C's capacity to attenuate loss of the HDL ability to prevent atherogenic modification of LDL (assessed as electrophoretic mobility) was, however, modest, and appeared limited only to those incubations in which HDL was exposed to lipophilic radicals. Our results indicate that vitamin C may, under some conditions, prevent loss of cardio-protective function from HDL during oxidant stress.

Effects of paraquat on the freshwater fish Channa punctata (Bloch): non-enzymatic antioxidants as biomarkers of exposure

Paraquat is a quaternary herbicide widely used for broadleaf weed control, which has been known to be a highly toxic compound for humans and animals. Therefore, analysis and development of biomarkers of exposure are undoubtedly valuable in evaluating the toxicity of paraquat contaminated water bodies. The effect of a single exposure of paraquat (1 ppm) for 24 h on various non-enzymatic antioxidants was studied in freshwater fish Channa punctata (Bloch). The levels of the reduced glutathione were significantly reduced in the liver and gill of exposed fish. The total and protein thiol levels were increased in all the tissues of the exposed fish. The non-protein thiol levels were reduced in liver and gill. The levels of ascorbic acid increased in liver. The uric acid level increased significantly in kidney and decreased significantly in gill of the exposed fish. The findings of the present investigation demonstrate the oxidative-stress-inducing potential of the herbicide paraquat in fish. This work indicated the possibility of using non-enzymatic antioxidants as biomarkers of exposure to environmental contamination and subsequent validation as a sensitive system for biomonitoring and ecotoxicological risk assessment.

Copper modulates non-enzymatic antioxidants in the freshwater fish Channa punctata (Bloch) exposed to deltamethrin

The assessment of the ecotoxicological risks caused by pesticides to ecosystems are based on data on the toxicity and effects of pesticide preparations to non-target organisms like fish. Deltamethrin is a widely used pesticide based on pyrethroids, which is reported to be extremely toxic to fish species. Modulatory effect of copper pre-exposure (10 ppb) on deltamethrin (0.75 microg l-1)-induced oxidative stress was investigated in freshwater fish Channa punctata (Bloch). Non-enzymatic antioxidants were studied as biomarkers of exposure to deltamethrin and possible protection afforded by copper pre-exposure. Glutathione levels were reduced significantly (P<0.05) in liver of copper-acclimatized deltamethrin-exposed group when compared with deltamethrin-exposed groups. The total thiol levels of copper-acclimatized deltamethrin-exposed group was significantly lowered (P<0.01) in liver when compared with deltamethrin-exposed group, while non-protein thiol levels recorded a significant (P<0.01) increase in liver of copper-acclimatized deltamethrin-exposed group when compared with deltamethrin-exposed group. The lipid peroxidation levels of copper-acclimatized deltamethrin-exposed groups were significantly lowered (P<0.01) in liver when compared with deltamethrin-exposed group. Deltamethrin is known to induce toxic responses by generating reactive oxygen species and to neutralize its toxic effect various non-enzymatic antioxidants were found to be modulated thus implicating their role as biomarkers in pollution control programmes.

Vitamin C Inhibits Lipid Oxidation in Human HDL

HDL are susceptible to oxidation, which affects their cardioprotective properties. Although several studies have reported inhibition of HDL oxidation by vitamin E, none has determined the potential protective effect of vitamin C, another important blood antioxidant. We investigated whether vitamin C protects HDL from oxidation by incubating HDL (0.2 g of protein/L) at 37 degrees C with cupric (Cu2+) ions (10 micromol/L) in the absence (control) or presence of vitamin C (20-200 micromol/L). In the absence of vitamin C, lipid oxidation in HDL began immediately and proceeded rapidly. Cholesteryl linoleate declined to a minimum, whereas lipid oxidation products (lipid dienes and TBARS) increased to near-maximal levels within 1 h. Vitamin C (50-200 micromol/L) retarded initiation of lipid oxidation for at least 4 h under the same conditions. The ability of vitamin C to preserve the cardioprotective antioxidant function of HDL was also assessed. HDL (0.5 g of protein/L) preincubated with Cu2+ (10 micromol/L) for 2 h in the absence of vitamin C lost antioxidant activity (45.4 +/- 6.2% inhibition of LDL oxidation compared with 93.2 +/- 3.6% for native HDL, P < 0.05). The addition of vitamin C (50-200 micromol/L) during preincubation of HDL with Cu2+, however, resulted in no significant loss of HDL antioxidant activity (77.3 +/- 0.3 to 89.8 +/- 5.4% inhibition of LDL oxidation, P > 0.05 compared with native HDL). Our results demonstrate that vitamin C inhibits lipid oxidation in HDL and preserves the antioxidant activity associated with this lipoprotein fraction.

Impaired cortical energy metabolism but not major antioxidant defenses in experimental bacterial meningitis

The loss of soluble brain antioxidants and protective effects of radical scavengers implicate reactive oxygen species in cortical neuronal injury caused by bacterial meningitis. However, the lack of significant oxidative damage in cortex [J. Neuropathol. Exp. Neurol. 61 (2002) 605-613] suggests that cortical neuronal injury may not be due to excessive parenchymal oxidant production. To see whether this tissue region exhibits a prooxidant state in bacterial meningitis, we examined the state of the major cortical antioxidant defenses in infant rats infected with Streptococcus pneumoniae. Adenine nucleotides were co-determined to assess possible changes in energy metabolism. Arguing against heightened parenchymal oxidant production, the high NADPH/NADP(+) ratio ( approximately 3:1) and activities of the major antioxidant defense and pentose phosphate pathway enzymes remained unchanged at the time of fulminant meningitis. In contrast, cortical ATP, ADP and total adenine nucleotides were on average decreased by approximately 25%. However, energy depletion did not lead to a significant decrease in adenylate energy charge (AEC). ATP depletion was likely a consequence of metabolic degradation, since it correlated with both the loss of total adenine nucleotides and accumulation of purine degradation products. Furthermore, the loss of ATP and decrease in AEC correlated significantly with the extent of neuronal injury. These results strongly suggest that energy depletion rather than parenchymal oxidative damage is involved in the observed cortical neuronal injury.

Vitamin C protects low-density lipoprotein from homocysteine-mediated oxidation

Homocysteine, an atherogenic amino acid, promotes iron-dependent oxidation of low-density lipoprotein (LDL). We investigated whether vitamin C, a physiological antioxidant, could protect LDL from homocysteine-mediated oxidation. LDL (0.2 mg of protein/ml) was incubated at 37 degrees C with homocysteine (1000 microM) and ferric iron (10-100 microM) in either the absence (control) or presence of vitamin C (5-250 microM). Under these conditions, vitamin C protected LDL from oxidation as evidenced by an increased lag time preceding lipid diene formation (> or = 5 vs. 2.5 h for control), decreased thiobarbituric acid-reactive substances accumulation (< or = 19 +/- 1 nmol/mg when vitamin C > or = 10 microM vs. 32 +/- 3 nmol/mg for control, p <.01), and decreased lipoprotein anodic electrophoretic mobility. Near-maximal protection was observed at vitamin C concentrations similar to those in human blood (50-100 microM); also, some protection was observed even at low concentrations (5-10 microM). This effect resulted neither from altered iron redox chemistry nor enhanced recycling of vitamin E in LDL. Instead, similar to previous reports for copper-dependent LDL oxidation, we found that vitamin C protected LDL from homocysteine-mediated oxidation through covalent lipoprotein modification involving dehydroascorbic acid. Protection of LDL from homocysteine-mediated oxidation by vitamin C may have implications for the prevention of cardiovascular disease.

Kinetics of the reactions of nitrogen dioxide with glutathione, cysteine, and uric acid at physiological pH

Nitrogen dioxide (NO(2)(*)) is a key biological oxidant. It can be derived from peroxynitrite via the interaction of nitric oxide with superoxide, from nitrite with peroxidases, or from autoxidation of nitric oxide. In this study, submicromolar concentrations of NO(2)(*) were generated in < 1 micros using pulse radiolysis, and the kinetics of scavenging NO(2)(*) by glutathione, cysteine, or uric acid were monitored by spectrophotometry. The formation of the urate radical was observed directly, while the production of the oxidizing radical obtained on reaction of NO(2)(*) with the thiols (the thiyl radical) was monitored via oxidation of 2,2'-azino-bis-(3-ethylthiazoline-6-sulfonic acid). At pH 7.4, rate constants for reaction of NO(2)(*) with glutathione, cysteine, and urate were estimated as approximately 2 x 10(7), 5 x 10(7), and 2 x 10(7) M(-1) s(-1), respectively. The variation of these rate constants with pH indicated that thiolate reacted much faster than undissociated thiol. The dissociation of urate also accelerated reaction with NO(2)(*) at pH > 8. The thiyl radical from GSH reacted with urate with a rate constant of approximately 3 x 10(7) M(-1) s(-1). The implications of these values are: (i) the lifetime of NO(2)(*) in cytosol is < 10 micros; (ii) thiols are the dominant 'sink' for NO(2)(*) in cells/tissue, whereas urate is also a major scavenger in plasma; (iii) the diffusion distance of NO(2)(*) is approximately 0.2 microm in the cytoplasm and < 0.8 microm in plasma; (iv) urate protects GSH against depletion on oxidative challenge from NO(2)(*); and (v) reactions between NO(2)(*) and thiols/urate severely limit the likelihood of reaction of NO(2)(*) with NO* to form N(2)O(3) in the cytoplasm.

Oxidative stress in brain during experimental bacterial meningitis: differential effects of alpha-phenyl-tert-butyl nitrone and N-acetylcysteine treatment

Antioxidant treatment has previously been shown to be neuroprotective in experimental bacterial meningitis. To obtain quantitative evidence for oxidative stress in this disease, we measured the major brain antioxidants ascorbate and reduced glutathione, and the lipid peroxidation endproduct malondialdehyde in the cortex of infant rats infected with Streptococcus pneumoniae. Cortical levels of the two antioxidants were markedly decreased 22 h after infection, when animals were severely ill. Total pyridine nucleotide levels in the cortex were unaltered, suggesting that the loss of the two antioxidants was not due to cell necrosis. Bacterial meningitis was accompanied by a moderate, significant increase in cortical malondialdehyde. While treatment with either of the antioxidants alpha-phenyl-tert-butyl nitrone or N-acetylcysteine significantly inhibited this increase, only the former attenuated the loss of endogenous antioxidants. Cerebrospinal fluid bacterial titer, nitrite and nitrate levels, and myeloperoxidase activity at 18 h after infection were unaffected by antioxidant treatment, suggesting that they acted by mechanisms other than modulation of inflammation. The results demonstrate that bacterial meningitis is accompanied by oxidative stress in the brain parenchyma. Furthermore, increased cortical lipid peroxidation does not appear to be the result of parenchymal oxidative stress, because it was prevented by NAC, which had no effect on the loss of brain antioxidants.

Marked elevation in cortical urate and xanthine oxidoreductase activity in experimental bacterial meningitis

Experimental bacterial meningitis due to Streptococcus pneumoniae in infant rats was associated with a time-dependent increase in CSF and cortical urate that was approximately 30-fold elevated at 22 h after infection compared to baseline. This increase was mirrored by a 20-fold rise in cortical xanthine oxidoreductase activity. The relative proportion of the oxidant-producing xanthine oxidase to total activity did not increase, however. Blood plasma levels of urate also increased during infection, but part of this was as a consequence of dehydration, as reflected by elevated ascorbate concentrations in the plasma. Administration of the radical scavenger alpha-phenyl-tert-butyl nitrone, previously shown to be neuroprotective in the present model, did not significantly affect either xanthine dehydrogenase or xanthine oxidase activity, and increased even further cortical accumulation of urate. Treatment with the xanthine oxidoreductase inhibitor allopurinol inhibited CSF urate levels earlier than those in blood plasma, supporting the notion that urate was produced within the brain. However, this treatment did not prevent the loss of ascorbate and reduced glutathione in the cortex and CSF. Together with data from the literature, the results strongly suggest that xanthine oxidase is not a major cause of oxidative stress in bacterial meningitis and that urate formation due to induction of xanthine oxidoreductase in the brain may in fact represent a protective response.

Role of oxidative stress in the selective toxicity of dieldrin in the mouse liver

Dieldrin, an organochlorine insecticide, induces hepatic tumors in mice but not in rats. Although the mechanism(s) responsible for this species specificity is not fully understood, accumulating evidence indicates that oxidative stress may be involved. This study examined the association of dieldrin-induced hepatic DNA synthesis with the modulation of biomarkers of oxidative damage to lipids (malondialdehyde [MDA]) and DNA (8-hydroxy-2-deoxyguanosine [oh8dG]), in male B6C3F1 mice and F344 rats fed dieldrin (0.1, 1.0, or 10 mg/kg diet) for 7, 14, 28, and 90 days. The nonenzymatic components of the antioxidant defense system (ascorbic acid, glutathione, and alpha-tocopherol) were also examined. Increased urinary MDA was observed in mice fed 0.1, 1.0, or 10 mg dieldrin/kg diet for 7, 14, 28, and 90 days; while increased hepatic MDA was seen only after 7 days in mice fed 0.1, 1.0, or 10 mg dieldrin/kg diet and after 14 days in mice fed 10 mg/kg diet. In rats, dieldrin had no effect on either hepatic MDA or urine MDA levels after 7, 14, and 28 days of treatment. A dose-dependent increase in urinary MDA was observed in rats at the 90-day sampling time. The only significant elevation in urinary or hepatic oh8dG content was limited to urinary oh8dG in mice fed 10 mg/kg dieldrin diet for 14 days. Dietary dieldrin produced sustained decreases in hepatic and serum alpha-tocopherol and sustained elevations in hepatic ascorbic acid in both mice and rats. Rats, however, possessed a three- to four-fold higher content of endogenous or basal (control) hepatic alpha-tocopherol; and, even when fed 10 mg dieldrin/kg diet, the levels of hepatic alpha-tocopherol were maintained at higher levels than those of mice fed control diet. In both rats and mice fed dieldrin, transient (14 and 28 days on diet) elevations in hepatic glutathione were observed. These data support the hypothesis that the species specificity of dieldrin-induced hepatotoxicity may be related to dieldrin's ability to induce oxidative stress in the liver of mice, but not in rats. Only in mice fed dieldrin was a temporal association of increases in hepatic MDA content and hepatic DNA synthesis seen, suggesting that oxidative damage (shown by increased lipid peroxidation) may be involved in early events in dieldrin-induced hepatocarcinogenesis. Rats may be protected from dieldrin-induced oxidative stress by a more effective antioxidant defense system, characterized by higher basal levels of hepatic alpha-tocopherol and ascorbic acid than that seen in the mouse.

The measurement of lipid peroxidation in vivo

Tissue damage due to free radical activity may be a common mediator in pathology [Kehrer, Crit. Rev. Toxicol. 23 (1993) 21-48]. The confirmation that free radicals have a role in the disease process is hampered by the difficulty of their measurement, as free radicals are transient species present at low concentrations in tissue. Direct measurement of free radicals is confined to electron spin resonance, a specialised methodology not available in our laboratory. We have evaluated several indirect measures, namely, changes in antioxidant status, hydroxyl radical trapping assays and monitoring breakdown products of free radical attack. Here we describe a method from the latter category, monitoring lipid peroxidation. The measurement of lipid peroxidation has been favoured as the indicator of free radical activity in previous ex vivo and in vitro studies of oxidative stress, in particular by the measurement of malondialdehyde (MDA). There is an absence of reported measurements of MDA from in vivo preparations especially where samples are collected in situ. The method describes the combination of microdialysis sampling with high performance liquid chromatography coupled to ultraviolet spectroscopy, to measure MDA from in vivo preparations of rat brain. The methodology could equally be applied to other tissues.

Impaired phosphatidylcholine biosynthesis and ascorbic acid depletion in lung during lipopolysaccharide-induced endotoxaemia in guinea pigs

Injection of guinea pigs with a single dose of Escherichia coli lipopolysaccharide (3.2 mg/100 g) induces a reversible endotoxic shock that was evaluated by measuring plasma glucose levels and aspartate aminotransferase activity at 24 h after lipopolysaccharide injection. The hypoglycaemia and the increase in plasma aminotransferase activity observed, correlated with the alterations found during the recovery phase of endotoxic shock. When lipid peroxidation and some antioxidant systems were measured in lungs from treated animals, we only found differences in ascorbic acid content, that was decreased by 50%. Lipopolysaccharide treatment results in a depression of pulmonary phosphatidylcholine synthesis, that correlates with the surfactant deficiencies associated with respiratory illnesses in septic shock. Guinea pigs fed on a diet with a low content in ascorbic acid were more sensitive to endotoxin. In these animals we found no detectable levels of ascorbic acid in lung, whereas both vitamin E lung levels and pulmonary phosphatidylcholine synthesis were significantly decreased. Our results point out the significance of ascorbic acid in the protection against oxidative lung injury associated to endotoxaemia, and validate our shock model for further studies on the mechanisms of this pathological condition.

Endotoxin depletes ascorbate in the guinea pig heart. Protective effects of vitamins C and E against oxidative stress

The effect of acute endotoxin-induced septic shock on myocardium oxidative stress after low or high vitamin C and/or E dietary supplementation was studied in guinea pigs, laboratory animals which, like human, do not have capacity for ascorbate synthesis. Neither the antioxidant enzymes or GSH were modified by endotoxin and vitamin treatments. Vitamin E showed a strong capacity to protect the myocardium against both enzymatic and non-enzymatic lipid peroxidation even in the presence of endotoxin. Vitamin C supplementation increased heart ascorbate whereas endotoxic shock totally depleted the heart ascorbate of vitamin C supplemented animals without changing vitamin E. Endotoxin significantly increased myocardium uric acid, a marker of ischemia induced oxidative stress, in animals fed with low vitamin C levels. This increase was totally prevented in vitamin C supplemented, but not in vitamin E supplemented animals. Strongly depressed levels of plasma vitamin C have been recently described in sepsis in human patients. The results suggest that ascorbate is a primary antioxidant target in the heart of endotoxin treated mammals lacking the capacity to synthesize ascorbate and that ascorbate can have a protective value against endotoxin-induced free radical damage in the myocardium. Implications of these results for the possible preventive role of vitamin C in humans during sepsis are discussed.

Acute acidosis elevates malonaldehyde in rat brain in vivo

Oxidative stress in brain tissue was measured experimentally in situ using microdialysis to sample the extracellular environment for a lipid peroxidation breakdown product and antioxidants. The extracellular concentrations of the lipid peroxidation product malonaldehyde (MDA) and the antioxidants ascorbic acid (AA) and uric acid (UA) were measured in rat cortex and striatum in vivo using microdialysis coupled to HPLC with UV detection. Tissue acidosis following ischaemia and epileptic seizures may contribute to neuronal damage, which may be mediated by reactive oxygen species. Perfusion of microdialysis probes with acidic artificial cerebrospinal fluid (pH 6) led to a significant increase in the sampled concentration of MDA and the antioxidant ascorbic acid. Simultaneous perfusion of ascorbate (5 mM) with acidic ACSF (pH 6) completely attenuated the rise in lipid peroxidation. This study provides in vivo evidence for acidosis induced oxidative stress in brain tissue and an antioxidant action of ascorbate. The methodology described here can provide direct in vivo information in respect of oxidative stress in experimental situations. The method could equally be applied to the assessment of oxidative stress in a number of pathological models not necessarily confined to the CNS.

Increase in heart glutathione redox ratio and total antioxidant capacity and decrease in lipid peroxidation after vitamin E dietary supplementation in guinea pigs

Dietary treatment with three diets differing in vitamin E, Low E (15 mg of vitamin E/kg diet), Medium E (150 mg/kg), or High E (1,500 mg/kg), resulted in guinea pigs with low (but nondeficient), intermediate, or high heart alpha-tocopherol concentration. Neither the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, and reductase, nor the nonenzymatic antioxidants, GSH, ascorbate, and uric acid were homeostatically depressed by increases in heart alpha-tocopherol. Protection from both enzymatic (NADPH dependent) and nonenzymatic (ascorbate-Fe2+) lipid peroxidation was strongly increased by vitamin E supplementation from Low to Medium E whereas no additional gain was obtained from the Medium E to the High E group. The GSH/GSSG and GSH/total glutathione ratios increased as a function of the vitamin E dietary concentration closely resembling the shape of the dependence of heart alpha-tocopherol on dietary vitamin E. The results show the capacity of dietary vitamin E to increase the global antioxidant capacity of the heart and to improve the heart redox status in both the lipid and water-soluble compartments. This capacity occurred at levels six times higher than the minimum daily requirement of vitamin E, even in the presence of optimum dietary vitamin C concentrations and basal unstressed conditions. The need for vitamin E dietary supplementation seems specially important in this tissue due to the low constitutive levels of endogenous enzymatic and nonenzymatic antioxidants present of the mammalian heart in comparison with those of other internal organs.

Detection of the lipid peroxidation product malonaldehyde in rat brain in vivo

The extracellular concentrations of the lipid peroxidation product malonaldehyde (MDA) and the antioxidants ascorbic and uric acid were measured in rat brain in vivo using microdialysis coupled to HPLC with ultra violet spectrophotometry. Treatment with kainic acid at pH 4.1 (50 nmol) caused a significant increase in the sampled concentration of MDA but no significant changes in the antioxidants. Treatment with the same dose of kainic acid at pH 7.2 did not cause a significant increase in MDA, although some changes were noted in the antioxidants. The paper demonstrates the ability to monitor changes of a lipid peroxidation breakdown product as a measure of oxidative stress in vivo. Furthermore, the data suggests that the toxic action of kainic acid in acute preparations may be due to the elevation of hydrogen ions.

Vitamin E protects guinea pig liver from lipid peroxidation without depressing levels of antioxidants

Oxidative stress is considered a pathogenic factor in many disorders. The capacity of dietary vitamin E to increase global antioxidant capacity and to decrease lipid peroxidation was studied in the guinea pig, an animal that cannot synthesize ascorbate. Male guinea pigs were subjected for 5 weeks to three diets differing in vitamin E content in the presence of optimum levels of vitamin C: group 15 (15 mg vitamin E/kg diet), group 150 (150 mg/kg), and group 1500 (1500 mg/kg). Hepatic vitamin E increased in the three groups in relation to the level of vitamin E in the diet. The increase in vitamin E between groups 15 and 150 was accompanied by a reduction in sensitivity to enzymatic lipid peroxidation. This did not occur between groups 150 and 1500. The different liver vitamin E concentrations did not affect the antioxidant enzymes superoxide dismutase, catalase, GSH-peroxidase and GSH-reductase, nor the non-enzymatic antioxidants vitamin C, GSH and ascorbate. It is concluded that dietary supplementation with vitamin E, at a level 6 times higher than the minimum daily requirement for guinea pigs, increases protection against hepatic lipid peroxidation without depressing endogenous antioxidant defences. Further increases in vitamin E to megadose levels did not provide additional protection from oxidative stress. The results also suggest that optimum levels of both vitamin C and vitamin E, simultaneously needed for protection against oxidative stress, are much higher than the minimum daily requirements.

Cytolysis does not per se induce lipid peroxidation: evidence in man

An increasing bulk of data counters the opinion that cell death and lysis necessarily trigger the formation and release of detectable amounts of molecules that are markers of lipid peroxidation. Plasma levels of thiobarbituric-acid-reacting compounds, protein-aldehyde fluorescent adducts, lipid peroxides, and endogenous antioxidant compounds were monitored versus controls, during intensive care treatment, in six patients seriously poisoned by ingestion of the mushroom Amanita Phalloides. All six patients showed cytolysis, and four of them massive tissue necrosis, as monitored in terms of serum transaminases. In all six patients, however, the blood parameters of redox equilibrium measured were within the normal range for the whole observation period.

Dietary vitamin C decreases endogenous protein oxidative damage, malondialdehyde, and lipid peroxidation and maintains fatty acid unsaturation in the guinea pig liver

Guinea pigs were fed during 5 weeks with three different levels of vitamin C in the diet: 33 (marginal deficiency), 660, or 13,200 mg of vitamin C per kg of diet. The group fed 660 mg of vitamin C/kg of diet showed strongly reduced levels of protein carbonyls (46% decrease), malondialdehyde (HPLC; 72% decrease), and in vitro production of TBARS (both stimulated with ascorbate-Fe2+ and with NADPH-ADP-Fe2+; 68% and 71% decrease), increased glutathione reductase activity, and increased vitamin C content (48 times higher) in the liver in relation to the group fed 33 mg/kg. The treatment with 660 mg of vitamin C/kg did not decrease any of the antioxidant defenses studied: superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, GSH, vitamin E, or uric acid. Further supplementation with 13,200 mg vitamin C/kg also reduced protein and lipid peroxidation, but decreased hepatic glutathione reductase and uric acid and resulted in a lower body weight of the animals. Both low (33 mg/kg) and very high (13,200 mg/kg) levels of vitamin C decreased body weight, glutathione reductase, and unsaturation of fatty acids in membrane lipids. The results show that a diet supplying an amount of vitamin C 40 times higher than the minimum daily requirement to avoid scurvy increases the global antioxidant capacity and is of protective value against endogenous lipid and protein oxidation in the liver under normal nonstressful conditions.

A decrease of free radical production near critical targets as a cause of maximum longevity in animals

A comprehensive study was performed on the brains of various vertebrate species showing different life energy potentials in order to find out if free radicals are important determinants of species-specific maximum life span. Brain superoxide dismutase, catalase, Se-dependent and independent GSH-peroxidases, GSH-reductase, and ascorbic acid showed significant inverse correlations with maximum longevity, whereas GSH, uric acid, GSSG/GSH, in vitro peroxidation (thiobarbituric acid test), and malondialdehyde (measured by HPLC), did not correlate with maximum life span. Superoxide dismutase, catalase, GSH-peroxidase, GSH and ascorbate results agree with those previously reported in various independent works using different animal species. GSSG/GSH, and true malondialdehyde (HPLC) results are reported for the first time in relation to maximum longevity. The results suggest that longevous species simultaneously show low antioxidant concentrations and low levels of in vivo free radical production (a low free radical turnover) in their tissues. The "free radical production hypothesis of aging" is proposed: a decrease in oxygen radical production per unit of O2 consumption near critical DNA targets (mitochondria or nucleus) increases the maximum life span of extraordinarily long-lived species like birds, primates, and man. Free radical production near these DNA sites would be a main factor responsible for aging in all the species, in those following Pearl's (Rubner's) metabolic rule as well as in those not following it.

Effect of dietary vitamin C and catalase inhibition of antioxidants and molecular markers of oxidative damage in guinea pigs

Guinea pigs were fed for five weeks with two diets with different levels of vitamin C, low (33 mg of Vit C/Kg diet) and high (13,200 mg of Vit C/Kg of diet). Catalase was inhibited with 3-amino-1,2,4-triazole (AT) in half of the animals from each dietary group. AT caused an almost complete depletion of liver catalase activity (90%) in both dietary groups. Vitamin C supplementation increased total glutathione peroxidase activity and tissue vitamin C level and decreased levels of protein carbonyls and malondialdehyde (MDA) in both treated and non-treated animals. This vitamin C supplementation did not change any of the other antioxidant defences studied. Our results show that dietary vitamin C supplementation increases global antioxidant capacity and decreases endogenous oxidative damage in the guinea pig liver under normal non-stressful conditions. This supports the protective value of dietary antioxidant supplementation.

Longevity and antioxidant enzymes, non-enzymatic antioxidants and oxidative stress in the vertebrate lung: a comparative study

It has been proposed that antioxidants can be longevity determinants in animals. However, no comprehensive study has been conducted to try to relate free radicals with maximum life span. This study compares the lung tissue of various vertebrate species--amphibia, mammals and birds--showing very different and well known maximum life spans and life energy potentials. The lung antioxidant enzymes superoxide dismutase, catalase, Se-dependent and non-Se-dependent glutathione peroxidases, and glutathione reductase showed significantly negative correlations with maximum life span. The same was observed for the lung antioxidants, reduced glutathione and ascorbate. It is concluded that a generalized decrease in tissue antioxidant capacity is a characteristic of longevous species. It is suggested that a low rate of free radical recycling (free-radical generation and scavenging) can be an important factor involved in the evolution of high maximum animal longevities. A low free-radical production could be responsible for a low rate of damage at critical sites such as mitochondrial DNA.

Compromised antioxidant status associated with ascites in broilers

Tissue infiltration by white blood cells in poultry with ascites has been reported, which could alter endogenous antioxidant status from oxidant stress. Therefore, the objective of this study was to determine the effect of ascites on ascorbic acid, tocopherol, and glutathione (GSH), which are major intracellular antioxidants. Broiler chicks (1 day) were placed in environmental chambers maintained with normal ventilation (Control) or under low ventilation, which produced a cumulative mortality of 31.3% due to ascites. At 3, 5, and 7 wk, lung and liver tissues were obtained from control birds (n = 5) and from birds in the low ventilation chamber with (ASC, n = 5) or without (NASC, n = 5) overt symptoms of ascites. There were no differences in tissue ascorbate, tocopherol, and GSH between the control and NASC groups with the exception of hepatic tocopherol at 7 wk, which was higher (P < .05) in NASC birds than in ASC and control birds. In general, lung and liver concentrations of all three antioxidants were lower (P < .05) in ASC birds than in NASC and control groups. Uric acid, a product of purine metabolism, was lower (P < .05) in liver and lung in ASC birds at 3 wk compared with control birds. However, uric acid concentrations in ASC birds were higher (P < .05) in the lung and serum at 5 wk, and in the liver at 7 wk compared with NASC and control birds.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of early maternal adrenalectomy on antioxidant enzymes, GSH, ascorbate, and uric acid in the rat fetal lung at term

Previous studies have shown that the increase of the enzymatic antioxidant defense that takes place in the fetal rat lung at the end of gestation can be accelerated by the synthetic glucocorticoid dexamethasone and diminished by metyrapone, a blocker of glucocorticoid synthesis. Since it is known that the fetal adrenal does not start to synthesize corticosterone until the last 20% of gestation, pregnant rats were bilaterally adrenalectomized on the first day of gestation in order to clarify the role of the endogenous maternal hormone on the development of the enzymatic and nonenzymatic antioxidant systems of fetal lung. This early adrenalectomy did not change fetal lung catalase, glutathione peroxidase, glutathione reductase, cytochrome oxidase, GSH, ascorbate, and uric acid at term. The presence of the maternal glands is not essential for lung antioxidant development in the fetus and that the stimulus of fetal corticosterone during the last 20% of gestation is enough to achieve a normal maturation of the fetal lung enzymatic and nonenzymatic antioxidant systems.

Maximum life span in vertebrates: relationship with liver antioxidant enzymes, glutathione system, ascorbate, urate, sensitivity to peroxidation, true malondialdehyde, in vivo H2O2, and basal and maximum aerobic capacity

In order to help clarify whether free radicals are implicated or not in the evolution of maximum life span (MLSP) of animals, a comprehensive study was performed in the liver of various vertebrate species. Strongly significant negative correlations against MLSP were found for hepatic catalase, Se-dependent and -independent glutathione peroxidases, and GSH, whereas superoxide dismutase, glutathione reductase, ascorbate, uric acid, GSSG/GSH, in vitro peroxidation (TBA-RS), and in vivo steady-state H2O2 concentration in the liver did not correlate with MLSP. Superoxide dismutase, catalase, glutathione peroxidase, and GSH results were in agreement with those independently reported by other authors, whereas the rest of our data are reported for the first time. Potential limitations arising from the use of animals of different vertebrate Classes were counterbalanced by the possibility to study animals with very different MLSPs and life energy potentials. Furthermore, the results agreed with previous data obtained using only mammals. Since liver GSSG/GSH, peroxidation, and specially H2O2 concentration were similar in species with widely different MLSPs, it is suggested that the decrease in enzymatic H2O2 detoxifying capacity of longevous species represents an evolutionary co-adaptation with a smaller in vivo rate of free radical generation. We propose the possibility that maximum longevity was increased during vertebrate evolution by lowering the rate of free radical recycling in the tissues.

Simultaneous induction of sod, glutathione reductase, GSH, and ascorbate in liver and kidney correlates with survival during aging

Catalase was continuously inhibited with aminotriazole in the liver and kidney during 33 months in large populations of old and young frogs in order to study the effects of the modification of the tissue antioxidant/prooxidant balance on the life span of a vertebrate species showing an oxygen consumption rate similar to that of humans. Free-radical-related parameters were measured during three consecutive years at 2.5, 14.5, and 26.5 months of experimentation. Aging per se did not decrease antioxidant enzymes and did not increase peroxidation (thiobarbituric acid positive substances, or high-pressure liquid chromatography [HPLC]-malondialdehyde), either cross sectionally or longitudinally. Long-term catalase inhibition leads to time-dependent increases (100-900%) of endogenous superoxide dismutase, GSH, ascorbate, and especially glutathione reductase at 2.5 and 14.5 months of experimentation. This was positively correlated with a higher survival of treated animals (91% in treated versus 46% in controls at 14.5 months of experimentation). The loss of those inductions after 26.5 months leads to a sharp increase in mortality rate. The results show for the first time that simultaneous induction of various tissue antioxidant enzymes and nonenzymatic antioxidants can increase the mean life span of a vertebrate animal. It is concluded that the tissue antioxidant/prooxidant balance is a strong determinant of mean life span.

A comparative study of free radicals in vertebrates--II. Non-enzymatic antioxidants and oxidative stress

1. The three main non-enzymatic endogenous soluble antioxidants and three estimators of oxidative stress were measured in the liver, lung and brain of seven animal species of different vertebrate classes. 2. The more concentrated antioxidant was GSH, followed by ascorbate and finally by uric acid. Liver showed higher levels of GSH and uric acid than the other two organs in the majority of the species. 3. GSSG/GSH ratio was highest in lung, probably due to the high pO2 prevalent in the tissue. Nevertheless, this did not result in higher tissue peroxidation, suggesting that the lung antioxidants are capable of coping with a high tissue pO2. 4. Tissue peroxidation was maximal in the brain when assayed by the TBA test, but this was not confirmed by HPLC of malondialdehyde (MDA). HPLC resulted in much lower MDA values than TBA.

Measurement of vitamin C by capillary electrophoresis in biological fluids and fruit beverages using a stereoisomer as an internal standard

Ascorbic acid (or vitamin C) is an important component of many biological systems and various physiological roles have been described for it. A rapid and simple capillary electrophoresis method for ascorbic acid measurements in biological fluids as well as in beverages was developed. A stereoisomer of ascorbic acid, isoascorbic acid, not normally found in nature, was used as the internal standard for this assay. The analysis was performed in a 30 cm x 75 microns I.D. fused-silica capillary with 100 mM tricine buffer, pH 8.8, and measured by UV absorbance at 254 nm. The method was sensitive to 1.6 micrograms/ml and linear to 480.1 micrograms/ml. Within-run R.S.D. was 3.2% (93.5 +/- 3.0 micrograms/ml, mean +/- S.D., n = 18) and run-to-run R.S.D. was 3.3% (35.6 +/- 1.2 micrograms/ml, mean +/- S.D., n = 10) and 1.9% (149.4 +/- 2.8 micrograms/ml, mean +/- S.D., n = 10). Average spiked recovery from human plasma samples was 98.0%. The technique has been demonstrated to be suitable for assay of vitamin C in biological samples and some fruit juices.