Ascorbic Acid Pretreatment Research Articles

Addition of Ascorbic Acid or Purified Kraft Lignin in Pulp Refining: Effects on Chemical Characteristics, Handsheet Properties, and Thermal Stability

The effects of two pulp pretreatments, impregnation with ascorbic acid (AA) or purified kraft lignin (KL), on bleached pulp refining were investigated by examining and testing handsheets made from these pulps. The AA pretreatment of the pulp amplified the depolymerization of the cellulose and notably impaired the strength properties of the pulp handsheets. The effects were enhanced upon the combination of the AA pretreatment and intensive refining. Furthermore, heat treatments (at 225 °C, 30 min, in water vapor atmospheres of 1 and 75% (v/v)) promoted the depolymerization of cellulose and the total color difference in the AA impregnated handsheets more than for the KL impregnated and reference handsheets. In contrast to AA, the KL pretreatment of the pulp improved the burst index stability of the refined pulp handsheets after the humid thermal treatment (75% (v/v)). In addition, the total color difference of the KL impregnated handsheets was lower than the AA impregnated and reference handsheets.

Transplantation of tendon-derived stem cells pre-treated with connective tissue growth factor and ascorbic acid in vitro promoted better tendon repair in a patellar tendon window injury rat model

Background aims. Treatment of tendon-derived stem cells (TDSCs) with connective tissue growth factor (CTGF) and ascorbic acid promoted their tenogenic differentiation. We investigated the effects of TDSCs pre-treated with CTGF and ascorbic acid on tendon repair in a patellar tendon window injury rat model. Methods. Green fluorescent protein-TDSCs (GFP-TDSCs) were pre-treated with or without CTGF and ascorbic acid for 2 weeks before transplantation. The patellar tendons of rats were injured and divided into three groups: fibrin glue–only group (control group), untreated and treated TDSC group. The rats were followed up until week 16. Results. The treated TDSCs accelerated and enhanced the quality of tendon repair compared with untreated TDSCs up to week 8, which was better than that in the controls up to week 16 as shown by histology, ultrasound imaging and biomechanical test. The fibrils in the treated TDSC group showed better alignment and larger size compared with those in the control group at week 8 (P = 0.004). There was lower risk of ectopic mineralization after transplantation of treated or untreated TDSCs (all P ≤ 0.050). The transplanted cells proliferated and could be detected in the window wound up to weeks 2 to 4 and week 8 for the untreated and treated TDSC groups, respectively. Conclusions. The transplantation of TDSCs promoted tendon repair up to week 16, with CTGF and ascorbic acid pre-treatment showing the best results up to week 8. Pre-treatment of TDSCs with CTGF and ascorbic acid may be used to further enhance the rate and quality of tendon repair after injury.

Trolox and ascorbic acid reduce direct and indirect oxidative stress in the IPEC-J2 cells, an in vitro model for the porcine gastrointestinal tract.

Oxidative stress in the small intestinal epithelium is a major cause of barrier malfunction and failure to regenerate. This study presents a functional in vitro model using the porcine small intestinal epithelial cell line IPEC-J2 to examine the effects of oxidative stress and to estimate the antioxidant and regenerative potential of Trolox, ascorbic acid and glutathione monoethyl ester. Hydrogen peroxide and diethyl maleate affected the tight junction (zona occludens-1) distribution, significantly increased intracellular oxidative stress (CM-H2DCFDA) and decreased the monolayer integrity (transepithelial electrical resistance and FD-4 permeability), viability (neutral red) and wound healing capacity (scratch assay). Trolox (2 mM) and 1 mM ascorbic acid pre-treatment significantly reduced intracellular oxidative stress, increased wound healing capacity and reduced FD-4 permeability in oxidatively stressed IPEC-J2 cell monolayers. All antioxidant pre-treatments increased transepithelial electrical resistance and viability only in diethyl maleate-treated cells. Glutathione monoethyl ester (10 mM) pre-treatment significantly decreased intracellular oxidative stress and monolayer permeability only in diethyl maleate-treated cells. These data demonstrate that the IPEC-J2 oxidative stress model is a valuable tool to screen antioxidants before validation in piglets.

Effect of organic acid pretreatment on some physical, functional and antioxidant properties of flour obtained from three unripe banana cultivars

Unripe banana flour (UBF) obtained from organic acid pretreatment of pulp from three non-commercial cultivars were profiled for physical, functional and antioxidant properties. UBF showed marked significant differences (p<0.05) in colour (CIEL∗a∗b∗ and CIELCH) and water holding capacity with no significant difference in oil holding capacity. The total polyphenol content (TPC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) differed significantly with M-red UBF recording high TPC (1130.39±27.26mg GAE/100g d.w.) at 10g/L citric acid pretreatment. Correlation analysis between TPC and DPPH showed very strong positive correlation for Mabonde UBF in citric and lactic acid pretreatment (r=0.999, p<0.01; r=0.985, p<0.01), while inverse correlation was recorded in M-red UBF for ascorbic and lactic acid pretreatment (r=−0.031; r=−0.137). Organic acid pretreatment enhances the physical and antioxidant properties of UBF hitherto absent in composite food formulations.

Chronic L-dopa decreases serotonin neurons in a subregion of the dorsal raphe nucleus.

L-Dopa (l-3,4-dihydroxyphenylalanine) is the precursor to dopamine and has become the mainstay therapeutic treatment for Parkinson's disease. Chronic L-dopa is administered to recover motor function in Parkinson's disease patients. However, drug efficacy decreases over time, and debilitating side effects occur, such as dyskinesia and mood disturbances. The therapeutic effect and some of the side effects of L-dopa have been credited to its effect on serotonin (5-HT) neurons. Given these findings, it was hypothesized that chronic L-dopa treatment decreases 5-HT neurons in the dorsal raphe nucleus (DRN) and the content of 5-HT in forebrain regions in a manner that is mediated by oxidative stress. Rats were treated chronically with l-dopa (6 mg/kg; twice daily) for 10 days. Results indicated that the number of 5-HT neurons was significantly decreased in the DRN after l-dopa treatment compared with vehicle. This effect was more pronounced in the caudal-extent of the dorsal DRN, a subregion found to have a significantly higher increase in the 3,4-dihydroxyphenylacetic acid/dopamine ratio in response to acute L-dopa treatment. Furthermore, pretreatment with ascorbic acid (400 mg/kg) or deprenyl (2 mg/kg) prevented the l-dopa-induced decreases in 5-HT neurons. In addition, 5-HT content was decreased significantly in the DRN and prefrontal cortex by l-dopa treatment, effects that were prevented by ascorbic acid pretreatment. Taken together, these data illustrate that chronic L-dopa causes a 5-HT neuron loss and the depletion of 5-HT content in a subregion of the DRN as well as in the frontal cortex through an oxidative-stress mechanism.

Effects of ascorbic acid on some physiological changes of pepino (Solanum muricatum Ait.) under chilling stress.

In this study, the changes caused by chilling stress on some physiological parameters of pepino (Solanum muricatum Ait.) plant and the effects of ascorbic acid (100 mM) applied exogenously on these changes were examined. For this purpose, the photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophylls and carotenoids), ascorbic acid, total phenolic compounds, malondialdehyde and proline contents in leaves of pepino taken on 5th and 10th days were determined. As a result of chilling stress, it was found that while the photosynthetic pigments and proline contents decreased in pepino leaves, the ascorbic acid, total phenolic compounds and malondialdehyde contents increased. In plants which were subjected to pre-treatment of ascorbic acid on the 10th day of stress, ascorbic acid and proline contents increased while a decrease was observed in malondialdehyde content, compared to stress group without pre-treated. This study may be important for explaining resistance induced by treatment of exogenous ascorbic acid in pepino exposed to chilling stress.

Influence of Priming Treatments on Stress Tolerance During Seed Germination of Rice

In many crop species, seed germination and early seedling growth are the most sensitive stages to any stress. In order to evaluate the effect of different seed priming techniques on germination of paddy under different temperatures a factorial experiment was conducted with six varieties. Seeds were primed for 12h in seven priming media (salicylic acid 50 ppm, ascorbic acid 200ppm, citric acid 200ppm, proline 0.2%, calcium chloride 2%, Na2HPO4 100ppm and distilled water) at three different temperatures (30°C, 38°C and 43°C) to observe the germination and related parameters. Results indicated that an increase in heat stress decreased germination components such as germination percentage, speed of germination, root length, shoot length and vigour index. Ascorbic acid and salicylic acid pre-treatment @ 200ppm and 50ppm respectively results in improvement of germination properties of paddy under heat stress condition because of its antioxidant capacity. The other treatments also enhanced the germination properties. Priming treatments including hydropriming resulted in the increased activity of α-amylase which in turn has resulted in better mobilization of stored carbohydrate reserves resulted in improvement of germination and other related parameters.

Role of ascorbic acid in counteracting ferric nitrilotriacetate-induced nephrotoxicity in rats

Context: Ascorbic acid (AA) is a naturally occurring organic compound with antioxidant properties. It is necessary for normal growth and development, and has been shown to protect against tissue toxicity and oxidative stress.Objective: The protective effect of AA against nephrotoxicity induced in albino rats by ferric nitrilotriacetate (Fe-NTA) was evaluated.Materials and methods: Male albino rats of Wistar strain (4–6 weeks old) weighing 125–150 g were used in this study. Animals were given a single dose of Fe-NTA (9 mg/kg body weight, intraperitoneal) after a week of treatment with AA (1 and 2 mg/animal/day).Results: Fe-NTA treatment enhanced microsomal lipid peroxidation (LPO) and hydrogen peroxide (H2O2) generation to 1.7- to 2.2-fold, glutathione (GSH) levels were decreased by two-fold and the activities of GSH metabolizing enzymes decreased to a range of 2.2- to 2.5-fold in renal tissue. These changes were reversed significantly in animals receiving pretreatment of AA. Treatment of rats with AA prior to the treatment with Fe-NTA decreased microsomal LPO and H2O2 generation to 124 and 172%, and also resulted in the recovery of reduced levels of GSH, GSH-metabolizing enzymes to almost 92% at the higher dose level of AA.Discussion and conclusion: AA protects against Fe-NTA-induced nephrotoxicity and renal damage. AA has a beneficial impact on Fe-NTA-induced toxicity due to its scavenging and antioxidant effect in albino rats.

Exploration of effects of emodin in selected cancer cell lines: enhanced growth inhibition by ascorbic acid and regulation of LRP1 and AR under hypoxia‐like conditions

This study explores the link between the antiproliferative activity of emodin through the generation of reactive oxygen species (ROS) in various cancer cell lines and the expression of the androgen receptor (AR) in the prostate cancer cell lines LNCaP (androgen-sensitive) and PC-3 (androgen-refractory), as well as the pro-metastatic low-density lipoprotein receptor-related protein 1 (LRP1) in the above prostate cancer cells and the nonprostate cell lines A549 (lung), HCT-15 (colon) and MG-63 (bone) under normoxic and hypoxia-like conditions. Among all cell lines, emodin showed most growth inhibition in LNCaP, followed by A549. The mechanism of cytotoxicity of emodin was postulated to be the widely reported ROS generation, based on the observations of poor in vitro radical-scavenging activity and increased growth inhibition of emodin by ascorbic acid (AA) pre-treatment owing to the additive effects of ROS generation by emodin and pro-oxidant effects of AA. Emodin downregulated AR in LNCaP under normoxic and hypoxia-like conditions (simulated by CoCl(2)) and LRP1 under normoxia. Emodin upregulated LRP1 in other cell lines, except HCT-15, under normoxic, and even more markedly under hypoxia-like conditions. The downregulation of AR in LNCaP and upregulation of LRP1 in all cell lines, except HCT-15, under hypoxia-like conditions along with growth inhibition by emodin, suggests that emodin may be a useful therapeutic option against androgen-sensitive prostate cancer and other such LRP1-expressing cancers to attempt the targeting of the elevated LRP1 levels to allow the uptake of emodin and/or any other accompanying therapeutic agents by LRP1.

Novel bisbenzimide-nitroxides for nuclear redox imaging in living cells

Nuclear oxidative stress damages genomic DNA and may lead to cell death, leading to aging and aging-related disorders. Though it is important to measure the nuclear oxidative stress separately, there are still little examples that applicable to living cells. We have designed and synthesized three bisbenzimide-nitroxides as probes to selectively visualize nuclear redox changes in terms of fluorescence. Compound 3, containing two radical moieties, showed the largest reduction-induced fluorescence change, with good localization in nuclei. RAW264.7 murine macrophage cells were loaded with compound 3 and then treated with 100μM hydrogen peroxide for 5min to show the fluorescence increase. This fluorescence increase was inhibited by pretreatment of 1mM ascorbic acid. These results show that compound 3 was suitable for nuclear-specific redox imaging in murine macrophages.

Prevention of Contrast-Induced Nephropathy with Ascorbic Acid

Some studies have shown that antioxidant ascorbic acid has renal protective effects, but the beneficial effects of contrast-induced nephropathy prevention remain to be clearly shown. Therefore, we aimed to determine whether ascorbic acid pretreatment reduces the risk of contrast-induced nephropathy in a high-risk population of patients with renal insufficiency undergoing coronary angiography. We conducted a prospective, randomized, controlled trial, involving 156 consecutive patients with chronic renal insufficiency (calculated estimated glomerular filtration rate<60 mL/min/1.73 m(2) and/or serum creatinine≥1.1 mg/dL) undergoing coronary angiography. Patients were randomized to ascorbic acid (n=74, 3 g intravenous injection before the procedure and oral 1 g per day for 2 days after the procedure, ascorbic acid group) or sodium chloride alone (n=82, control group). All patients received pre-and postprocedure hydration. There was no difference between the ascorbic acid group and control group in mean peak increase in serum creatinine measured within 48 hours after coronary angiography, the primary study end point (0.012±0.146 vs 0.022±0.212 mg/dL respectively, p=0.216). The incidence of contrast-induced nephropathy, a secondary end point defined as increase of either≥25% or ≥0.5 mg/dL in serum creatinine, was 5.4% in ascorbic acid-treated patients (4/74) and 6.3% in control group patients (6/82), a nonsignificant difference (p=0.690). There were also no differences between the 2 groups in the inhospital clinical outcomes or length of hospital stay. Ascorbic acid pretreatment for short-term at high dose do not prevent renal function deterioration after administration of contrast medium in patients with baseline renal insufficiency undergoing coronary angiography.

Enhancement of salt tolerance in sugarcane by ascorbic acid pretreatment

Ascorbic acid is a non-enzymatic antioxidant which plays an important role in the activation of biological defense mechanisms. The effect of 24 h ascorbic acid (0.5 mM) pretreatment was observed on subsequent growth and development of callus cultures as well as in vitro -grown plants of Saccharum sp. hybrid (cvs. HSF 240 and SPF 234). After pretreatment, callus cultures of HSF 240 were transferred to 80, 100 and 120 mM sodium chloride (NaCl) while those of SPF 234 were subjected to 100, 120 and 140 mM NaCl concentrations. The in vitro -grown plants were also transferred to the saltcontaining media (0 to 160 mM; nine treatments) after ascorbic acid pretreatment. Ascorbic acid pretreatment to callus cultures resulted in more browning and necrosis. Pretreated in vitro -grown plants of both the sugarcane cultivars survived higher NaCl level and showed much less yellowing of leaves as compared to non-pretreated controls. Ascorbic acid pretreatment to in vitro- grown plants of cv. HSF 240 had a significant effect on catalase and peroxidase (POD) activities while in cv. SPF 234 a significant effect on root length, soluble protein contents as well as antioxidant enzyme activities was recorded. Hence both morphological as well as biochemical parameters studied during the present work suggested that ascorbic acid pretreatment of in vitro -grown sugarcane plants may enhance their salt tolerance. Key words: Antioxidant enzymes, callus, protein content, salt stress.

The protective effects of ascorbic acid, cimetidine, and nifidipine on diethyldithiocarbamate-induced hepatic toxicity in albino rats

The aim of the present work was to clarify the involvement of free radicals, cytochrome P450 toxic metabolites, and deregulation of calcium homeostasis in the mechanism of diethyldithiocarbamate (DDC) hepatotoxicity. This was elucidated through the preadministration of ascorbic acid (a free radical scavenger), cimetidine (an inhibitor of cytochrome P450 enzymes), or nifedipine (a calcium-blocking agent) before DDC treatment to male albino rats. DDC was administered either as a single dose [800 mg/kg body weight (b.w.), subcutaneously, s.c.] or daily repeated doses for 30 days (400 mg/kg b.w., s.c.). Oxidative stress indicators [e.g., malondialdehyde (MDA), reduced glutathione (GSH), and superoxide dismutase enzyme (SOD)] showed that single or repeated DDC doses induce an increase in MDA level and a decrease in SOD activity in the liver, whereas it causes depletion in hepatic GSH after a single dose and an elevation in its value after repeated doses. Severe histopathological changes were also observed in the livers of rats treated with single or repeated DDC doses. Ascorbic acid, cimetidine, and nifedipine pretreatments were found to induce highly protective effects against the evinced DDC hepatotoxicity, manifesting that free radical, cytochrome P450, and calcium-dependent processes contribute to DDC liver toxicity. Finally, although multiple mechanisms may be involved in the hepatotoxic changes induced by DDC, calcium disarrangement and free radical formation play a more critical role than cytochrome P450 in metabolic events leading to toxic effects of DDC.

Impact of short-duration administration of N-acetylcysteine, probucol and ascorbic acid on contrast-induced cytotoxicity

The best pharmaceutical prevention of contrast-medium-induced nephropathy for emergency procedures remains unknown. The aim of this study was to examine the impact of short-duration antioxidant pretreatment on contrast-medium-induced cytotoxicity. Human embryonic kidney cells were treated with three different contrast media: ionic ioxitalamate, non-ionic low-osmolar iopromide, and iso-osmolar iodixanol. The doses and durations of pretreatment with antioxidants were 2 mM/L N-acetylcysteine for 15 minutes, 40 µM/L probucol for 30 minutes, and 30 µM/L ascorbic acid for 30 minutes. A supplementary dose of 2 mM/L N-acetylcysteine was administered 12 hours after contrast medium treatment. Cell viability was determined by tetrazolium MTT assay. All three contrast media caused significant reduction of cell viability at 24 hours (p<0.001). In the groups receiving iopromide or iodixanol, N-acetylcysteine pretreatment significantly improved cell viability compared with no N-acetylcysteine pretreatment (p<0.001). In the group receiving ioxitalamate, N-acetylcysteine pretreatment followed by a supplementary dose of N-acetylcysteine at 12 hours rather than N-acetylcysteine pretreatment alone significantly improved cell viability compared with no N-acetylcysteine pretreatment (p=0.038). Probucol or ascorbic acid pretreatment was unable to reduce cell death caused by the three contrast media. Short-duration pretreatment with N-acetylcysteine significantly reduced contrast-medium-induced cytotoxicity. These findings provide new insight into the prevention of contrast-medium-induced nephropathy in clinical emergency scenarios.

Antioxidant effects of heated garlic juice on cadmium-induced liver damage in rats as compared to ascorbic acid

The antioxidant efficacy of heated garlic juice (HGJ) in liver was evaluated with that of ascorbic acid (AA) in rats exposed to acute dose of cadmium (4 mg kg(-1) bd. wt). The rats were either given HGJ (100 mg kg(-1) bd. wt) orally, daily for 4 weeks or AA (100 mg kg(-1) bd. wt) orally, daily for 4 weeks or both or cadmium (4 mg kg(-1) bd. wt) intraperitoneally for 3 days. Another group of rats was given cadmium (4 mg kg(-1) bd. wt) intraperitoneally for 3 days after pretreatment with either HGJ (100 mg kg(-1) bd. wt) or ascorbic acid (100 mg kg(-1) bd. wt) for 4 weeks and the liver excised. The results obtained show that AA and HGJ significantly reduced the level of liver malondialdehyde (MDA) induced by cadmium compared to control (p < 0.05) but AA tends to be more potent when compared with HGJ. The presence of either HGJ or AA also significantly reduced the levels of ROS in the presence of cadmium (Cd). The presence of either AA or HGJ pre-treatment produced significant increase in liver SOD and Catalase activities when compared with rats treated with Cd alone. There was no significant reduction in the activities of these enzymes in the presence of cadmium compared to control. Western blot shows that the expressions of Nrf2 and NQO1 in the liver were significantly increase by 3 and 1.7-fold respectively in the AA pretreated mice when compared with Cd. However no significant changes were seen in HGJ pretreated rats. The expression of HO-1 was not significantly increase in the AA pretreated rats. The results show that though both ascorbic acid and HGJ are efficient in preventing Cd-induced damage in the rat liver, ascorbic acid appeared to be a more powerful antioxidant than heated garlic juice in preventing cadmium-induced oxidative damage in liver and its action may be mediated in parts via Nrf2-keap1 pathway.

The decline in ascorbic acid content is associated with cadmium toxicity of rice seedlings

Cadmium (Cd) toxicity of rice (Oryza sativa L. cv. Taichung Native 1) seedlings was evaluated by the decrease in chlorophyll content and the increase in malondialdehyde (MDA) in the second leaves of rice seedlings. CdCl2 (5 microM) treatment was accompanied by a decrease in the contents of ascorbic acid (AsA) and AsA + dehydroascorbate (DHA) and in the ratios of AsA/DHA in leaves. However, CdCl2 treatment resulted in an increase in DHA content in leaves. Moreover, the decrease in AsA content was prior to the occurrence of chlorosis and associated with the increase in MDA content in the leaves of seedlings treated with Cd. Pretreatment with 0.5 mM AsA or L-galactono-1,4-lactone (GalL), the biosynthetic precursor of AsA, for 6 h resulted in an increase in the contents of AsA and reduced glutathione (GSH), the ratios of AsA/DHA and GSH/oxidized glutathione, and the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) in the leaves of rice seedlings. Quantitative RT-PCR was applied to quantify the mRNA levels for OsAPX and OsGR genes from rice leaves to examine the effect of AsA or GalL pretreatment on the expression of OsAPX and OsGR genes in rice leaves. The expression of OsAPX2, OsAPX3, OsAPX4, OsAPX5, OsAPX6, OsAPX7, and OsGR1 was increased by AsA or GalL pretreatment. Rice seedlings pretreated with AsA or GalL were observed to reduce the subsequent Cd-induced toxicity. Our results suggest that AsA content may play a role in regulating Cd toxicity of rice seedlings.

Free radicals mediate postshock contractile impairment in cardiomyocytes*

Previous studies demonstrated myocardial dysfunction after electrical shock and indicated it may be related to free radicals. Whether the free radicals are generated after electrical shock has not been documented at the cellular level. This study was to investigate whether electrical shock generates intracellular free radicals inside cardiomyocytes and to evaluate whether reducing intracellular free radicals by pretreatment of ascorbic acid would reduce the contractile dysfunction after electrical shock. Randomized prospective animal study. University affiliated research laboratory. Sprague-Dawley rats. Cardiomyocytes isolated from adult male rats were divided into four groups: (1) electrical shock alone; (2) electrical shock pretreated with ascorbic acid; (3) pretreated with ascorbic acid alone; and (4) control. Ascorbic acid (0.2 mM) was administrated in the perfusate of the ascorbic acid + electrical shock and ascorbic acid groups. A 2-J electrical shock was delivered to the electrical shock and ascorbic acid + electrical shock groups. DCFH-DA-loaded cardiomyocytes showed increased intracellular free radicals after electrical shock. The contractions and Ca2+ transients were recorded optically with fura-2 loading. Within 4 mins after electrical shock in the electrical shock group, the length shortening decreased from 8.4% +/- 2.5% to 5.6% +/- 3.4% (p = 0.000) and the Ca2+ transient decreased from 1.15 +/- 0.13 au to 1.08 +/- 0.1 au (p = 0.038). Compared with control, a significant difference in length shortening (p = 0.001) but not Ca2+ transient (p = 0.052) was noted. In the presence of ascorbic acid, electrical shock did not affect length shortening and Ca2+ transient. Electrical shock generates free radicals inside the cardiomyocyte, and causes contractile impairment and associated decrease of Ca transient. Administering ascorbic acid may improve such damage by eliminating free radicals.

Free Radical Scavenging and Antioxidant Activity of Ascorbigen Versus Ascorbic Acid: Studies in Vitro and in Cultured Human Keratinocytes

Ascorbigen (ABG) is formed by indole-3-carbinole and ascorbic acid in brassica vegetables. In the present study, ABG has been systematically analyzed for its free radical scavenging and antioxidant capacity. To directly measure the free scavenging activity of ABG and ascorbic acid (used as a positive control), electron spin resonance and spin trapping experiments were performed. Ascorbic acid exhibited a potent free radical scavenging activity, whereas ABG did not scavenge superoxide anion free radicals and showed only little scavenging activity toward 2,2-diphenyl-1-picrylhydrazyl free radicals. Similar data were obtained for the ferric reducing ability of plasma and trolox equivalent antioxidant capacity assays. In cultured human keratinocytes, ABG counteracted tert-buthylhydroperoxide-induced cytotoxicity, whereas ascorbic acid did not exhibit any protective activity. Furthermore, in ABG-treated human keratinocytes, a decrease in tert-buthylhydroperoxide-induced lipid peroxidation was detected, whereas an ascorbic acid pretreatment did not result in the prevention of lipid peroxidation. These data indicate that ascorbic acid seems to be a more potent free radical scavenger than ABG in vitro, while ABG prevented tert-buthylhydroperoxide cytotoxicity more effectively as compared to ascorbic acid in cultured cells.

Abstract P21: Free Radicals Mediate Post-shock Contractile Impairment in Cardiomyocytes

Background Previous studies demonstrated myocardial dysfunction after electrical shock and indicated that it may be related to the generation of free radicals. Whether the free radicals are generated after electrical shock has not been documented at the cellular level and its effect on post-shock contractile function has not been clarified. Hypothesis : Electrical shock generates intracellular free radicals inside cardiomyocytes. Reducing intracellular free radicals by pre-treatment of ascorbic acid (AA) would reduce the contractile dysfunction following electrical shock. Methods : Cardiomyocytes isolated from adult male rats were divided into 4 groups, (1) electrical shock alone, (2) electrical shock pre-treated with AA, (3) pre-treated with AA alone and (4) control. AA was administered in an amount of 0.2 mM into the perfusate of the AA + electrical shock and AA groups. Electrical shock of 2 J was delivered in the electrical shock and AA+ electrical shock groups. Results : DCFH-DA loaded cardiomyocytes showed increased intracellular free radicals after electrical shock. The length shortening and Ca 2+ transients were recorded optically with fura-2 loading. Within 4 minutes following electrical shock in the electrical shock group, the length shortening decreased from 8.4±2.5% to 5.6±3.4% ( P =0.000) and the Ca 2+ transient decreased from 1.15±0.13 au to 1.08±0.1 au ( P =0.038). Compared with control, a significant difference in length shortening ( P =0.001) and Ca 2+ transient ( P =0.052) was observed. In the presence of AA, electrical shock did not affect length shortening and Ca 2+ transient. Conclusion: Electrical shock generates intracellular free radicals inside the cardiomyocyte. This is associated with contractile impairment and decrease of Ca 2+ transient. Administering AA may decrease such damage by eliminating free radicals.

Protective Effects of Combined Ischemic Preconditioning and Ascorbic Acid on Mitochondrial Injury in Hepatic Ischemia/Reperfusion

This study examined the in vivo effects of ischemic preconditioning (IPC), ascorbic acid (AA), or a combination (IPC + AA) on the level of mitochondrial injury caused by hepatic ischemia/reperfusion (I/R). A rat liver was preconditioned with 10 min of ischemia followed by 10 min of reperfusion, and then subjected to 90 min of ischemia followed by 5 h of reperfusion. The rats were pretreated with AA (100 mg/kg, i.v.) 5 min before the sustained ischemia. I/R increased the aminotransferase activity and level of mitochondrial lipid peroxidation, whereas it decreased the reduced glutathione:oxidized glutathione ratio. Either the IPC or AA pretreatment alone attenuated these changes, with the effect being enhanced by IPC + AA. The level of mitochondrial glutamate dehydrogenase, which is specifically located in the matrix, decreased after I/R but this was prevented by IPC + AA. Significant peroxide production was observed after 10 min of reperfusion after sustained ischemia. This change was attenuated by either IPC or AA alone and was further attenuated by IPC + AA. The mitochondria isolated after I/R were rapidly swollen, indicating an opening of the permeability transition pore. However, this was markedly reduced by IPC + AA. The hepatic ATP level was lower after I/R, which was restored by IPC alone and IPC + AA. Our findings suggest that IPC and AA synergistically reduce the level of mitochondrial damage during I/R as a result of decreased postischemic oxidant stress.