The purpose of this study was, first to explore metabolic interactions between Cu and ascorbic acid in guinea-pigs, particularly with respect to any possible disadvantages of high ascorbate in the presence of low Cu intakes, and second, to test the hypothesis that variations in ascorbate and/or Cu status might influence collagen cross-linking, either by inducing a change in the crosslinks: hydr...

Cytochrome P450 (CYP) 2E1 was the most efficient CYP enzyme that oxidized benzene to soluble and covalently bound metabolites in rat and human liver microsomes. The covalent binding was due mostly to the formation of benzoquinone (BQ), the oxidation product of hydroquinone (HQ), and was inversely related to the formation of soluble metabolites. In rats, inhalation of benzene (4 mg/liter of air)...

Studies were carried out to determine the actions of and interactions between ascorbate, NADPH, Fe2+, and Fe3+ on lipid peroxidation in adrenal and testicular microsomes. Ascorbate-induced malonaldehyde production was maximal in adrenal and testicular microsomes at an ascorbate concentration of 1 X 10(-4)M. Fe2+, at levels between 10(-6) and 10(-3)M, produced concentration-dependent increases i...

Ascorbic acid has been shown to stimulate endothelial nitric oxide (NO) synthesis in a time- and concentration-dependent fashion without affecting NO synthase (NOS) expression or l-arginine uptake. The present study investigates if the underlying mechanism is related to the NOS cofactor tetrahydrobiopterin. Pretreatment of human umbilical vein endothelial cells with ascorbate (1 microm to 1 mm,...

The effect of salinity on the antioxidative system of root mitochondria and peroxisomes of a cultivated tomato Lycopersicon esculentum (Lem) and its wild salt-tolerant related species L. pennellii (Lpa) was studied. Salt stress induced oxidative stress in Lem mitochondria, as indicated by the increased levels of lipid peroxidation and H(2)O(2). These changes were associated with decreased activ...

The objective of this study is to determine the influence of several personal and lifestyle factors on the levels of circulating vitamin C in a population of children. To accomplish this objective, blood samples were collected from 511 healthy children residing in the Greater San Juan area. The population was stratified into 4 percentile groups (approaching quartiles) according to plasma ascorb...

Kiwifruit are a rich source of vitamin C and also contain numerous phytochemicals, such as flavonoids, which may influence the bioavailability of kiwifruit-derived vitamin C. The aim of this study was to compare the relative bioavailability of synthetic versus kiwifruit-derived vitamin C using a randomised cross-over pharmacokinetic study design. Nine non-smoking males (aged 18-35 years) receiv...

Ascorbate has previously been shown to enhance both alpha(1)- and beta(2)-adrenergic activity. This activity is mediated by ascorbate binding to the extracellular domain of the adrenergic receptor, which also decreases the oxidation rate of ascorbate. H1 histamine receptors have extracellular agonist or ascorbate binding sites with strong similarities to alpha(1-) and beta(2)-adrenergic recepto...

Changes in the endogenous ascorbate redox status through genetic manipulation of cellular ascorbate levels were shown to accelerate cell proliferation during the induction phase and improve maturation of somatic embryos in Arabidopsis. Mutants defective in ascorbate biosynthesis such as vtc2-5 contained ~70 % less cellular ascorbate compared with their wild-type (WT; Columbia-0) counterparts. D...

Plants have developed various mechanisms to protect themselves against oxidative stress. One of the most important non-enzymatic antioxidants is ascorbic acid. There is thus a need for a rapid, sensitive method for the analysis of the reduced and oxidised forms of ascorbic acid in crop plants. In this paper a simple, economic, selective, precise and stable HPLC method is presented for the detec...