High doses of synthetic antioxidative vitamins: A, E, C and β-carotene are often used on long-term basis in numerous preventive and therapeutic medical applications. Instead of expected health effects, the use of those vitamins may however lead to cases of hypervitaminosis and even to intoxication. The article points out main principles of safety which are to be observed during supplementation with antioxidative vitamins. Toxic effects resulting from erroneous administration of high doses of those substances on organs and systems of the organism are also discussed. Attention is drawn to interactions of antioxidative vitamins with concomitantly used drugs, as well as intensification of adverse effects caused by various exogenous chemical factors. Moreover, the article presents the evaluation of supplementation with these vitamins, which was performed in large studies.
Voa1 and Voa2 cooperatively regulate the acidification and transmitter uptake/storage of dense-core vesicles, although they might not be as critical for exocytosis as recently proposed.
The phosphotungstate reagent (PTR) was used for quantitative spectrophotometric determination of physiological forms of vitamin C in blood plasma. An immediate action of PTR on the first half of the tested samples allowed to determine reduced vitamin C concentrations (I) at 700 nm. 10 mм dithiothreitol added to the second half of the samples reduced oxidized vitamin C in it - hence the total amount of this vitamin was reduced with a concentration (II) determined as above (remains of dithiothreitol were removed with N-ethylmaleimide). The difference of results (II) and (I) gave the concentration of oxidized vitamin C. The method is characterised by fault-less analytical parameters: correlation coefficients of analytical curves > 0.99, recovery factor 100.5%, variation coefficients intra- and inter-serial < 3% and < 5%, respectively, detection limit 0.05 μm. The simplicity of the method enables an easy control of the ratio of oxidized and reduced vitamin C concentrations in blood plasma - the biomarker of the level of oxidative damage to cells.
IntroductionCancer cells, compared to normal cells, are under increased oxidative stress associated with oncogenic transformation, alterations in metabolic activity, and increased generation of reactive oxygen species.Material and methodsWe investigated the ability of vitamin C to reduce the damage induced by hydrogen peroxide, in human colorectal adenocarcinoma cells in vitro by the comet assay. Additionally, we measured the kinetics and efficacy of the repair of DNA damage after incubation with vitamin C in the presence of H2O2.ResultsThe obtained results showed that 1 h pre-incubation with vitamin C and exposure to H2O2 for the last 10 min of incubation caused a statistically significant (p < 0.05) increase in DNA migration in comet tails in all experimental series. For the 10 µM, 25 µM, 50 µM, 100 µM vitamin C concentrations the levels of DNA damage were as follows: 18.6%, 21.1%, 25.3% and 27.2%, respectively, as compared to the untreated cells (3.26%). However, in comparison with H2O2 alone (29.1%), we observed a statistically significant (p < 0.05) decrease of the genotoxic effect in HT29 cells induced by H2O2 for the two lowest of concentrations of vitamin C: 10 µM and 25 µM. The HT29 cells were able to achieve effective repair of the damaged DNA within 60 and 120 min after incubation with the tested compounds. All the values obtained in the test were statistically significant (p < 0.05).ConclusionsVitamin C caused a weaker DNA damaging effect of hydrogen peroxide and positively influences the level of oxidative DNA damage in HT29 cells (decrease ∼ 30%). We noted that DNA damage was effectively repaired during 120 min postincubation in the tested cells and that oxidative damage was the major type of damage.
Colorectal cancer is a major public health concern particularly in developed countries. Despite decades of advances in the treatment and prevention of colorectal cancer, it remains the second most common cause of cancer death. There now exists convincing evidence that reactive oxygen species play an important role in the etiology and progression of a number of human diseases including colorectal cancer. Reactive oxygen species may damage all types of biological molecules. However, proteins are possibly the most immediate vehicle for inflicting oxidative damage on cells since they are often catalysts rather than stoichiometric mediators, hence, the effect of damage to one molecule is greater than stoichiometric. the aim of the study was to investigate oxidative protein damage in patients with colorectal cancer and its correlation with the clinical stage of the disease. material and methods. The study group comprised 102 patients operated on for colorectal cancer in different clinical stages of the disease. Plasma carbonyl levels were determined using Levin's method. results. Patients in all tumor groups showed significantly higher levels of plasma carbonyls when compared to healthy people. We observed an increase in mean plasma carbonyl levels correlating with an increase in the degree of disease advancement. Conclusions. This study demonstrates that reactive oxygen species may have a role in pathogenesis of colorectal cancer. The outcomes of this research seem to confirm that antioxidants may play a role in chemoprevention of colorectal cancer.
The usefulness of phosphotungstate reagent for vitamin C determination in tissue homogenates has been confirmed. An optimal homogenization medium was selected: 1.8 m solution of HPO 3 in 1.3 m CH 3 COOH. With this medium the analytical curve (at 700 nm) demonstrated the right linearity, correlation and recovery coefficients were appropriately high (0.999 and 99.8%) and the values of intraserial and interserial variation coefficient were low (< 5% and < 10%, respectively). It makes this method sensitive, easily repeatable, and useful for vitamin C determination in animal and human tissues, including neoplastic ones.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.