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PubMed1990

Intestinal absorption and metabolism of ascorbic acid in rainbow trout.

Transport and metabolism of the reduced and oxidized forms of vitamin C were evaluated in trout intestine in vitro. Transepithelial fluxes of [14C]ascorbic acid were determined with the substrate present at 10 microM. The mucosa-to-serosa flux was fourfold greater than the serosa-to-mucosa flux with ascorbic acid present in both bathing solutions. Cellular accumulation of the reduced molecule occurred with a final tissue-to-medium ratio of 1.64. Ascorbic acid influx across the brush-border membrane was determined under conditions that inhibit transport of other nutrients. Influx was not reduced because of the presence of the D- or L-stereoisomeric form of glucose but was highly dependent on the presence of Na in the bathing medium. Brush-border influx was saturable with a Km of 220 microM. Short-term (8 min) exposure of intestinal loops to the oxidized form of vitamin C, dehydro-L-ascorbic acid, was followed by high-performance liquid chromatography analysis of the 14C label present in the tissue. Total uptake of substrate was greater from the serosal solution than from the mucosal solution; in either situation most of the 14C label was found in the reduced state. It is concluded that transport and metabolic capabilities are present in the trout intestine to absorb oxidized and reduced forms of vitamin C and to help regulate the redox potential of circulating ascorbic acid by recycling dehydro-L-ascorbic acid.

Absorption↗
PubMed1989

Renal metabolism of the oxidized form of ascorbic acid (dehydro-L-ascorbic acid).

We evaluated whether specific transport and metabolic properties exist in rat and guinea pig kidney for handling the immediate oxidative product of ascorbic acid, dehydro-L-ascorbic acid. Isolated tubules were used to measure uptake of 10 microM [14C]-dehydro-L-ascorbic acid over an 8-min incubation period. Uptake did not show dependence on the bathing media electrolyte composition but was inhibited to some extent by glucose. In tubules of both animal species the majority of 14C label present in the tissue extract was in the reduced form. No degredative enzymatic effect on dehydro-L-ascorbic acid is evident. Thirty-six percent of the [14C]dehydro-L-ascorbic acid reduced by the tubules was released during an 8-min incubation. Recently formed ascorbic acid is not substantially bound to cellular components. A factor necessary for dehydro-L-ascorbic acid reduction in renal cortex was found primarily in the 55-70% ammonium sulfate fraction. It is retained by mol wt 12,000 dialysis tubing, is heat labile, pH sensitive, inhibited by thiol reagents, and is most active in the presence of NADPH and glutathione. It has a molecular weight between that of blue dextran and cytochrome c as indicated by gel chromatography. We suggest that a cytosolic enzyme functions in reduction of dehydro-L-ascorbic acid and thereby is important in maintaining the redox state of ascorbic acid derived from the glomerular filtrate or from peritubular fluid.

Animals↗
PubMed2005

[Malondialdehyde and reduced glutathione increase in patients with chronic stable ischaemic cardiopathy].

BACKGROUND AND OBJECTIVE: Cardiovascular diseases are associated with the ischemia/reperfusion phenomena and therefore to the oxidation/antioxidation balance. The aim of this study was to determine malondialdehyde, nitric oxide, glutathione, ascorbic and dehydroascorbic acid in patients with chronic ischemic heart disease. PATIENTS AND METHOD: 32 male patients, with chronic ischemic heart disease, between 40 and 60 years of age were studied. These individuals were divided in two groups: 16 with hypertension and 16 without hypertension. Both groups were compared with 31 healthy male subjects (control group). RESULTS: Significant differences (p < 0.001) was observed in malondialdehyde between no-hypertension ischemic group: 5.3 (1.5) microM and the hypertension ischemic group: 4.8 (1.3) microM in contrast with the healthy group: 2.2 (0.5) microM. Hypertension ischemic group showed significant greater reduced glutation levels: 286.1 (31.4) microg/ml than control group 262.0 (38.8) microg/ml; p < 0.03 and no-hypertension ischemic group: 256.4 (41.5) microg/ml; p < 0.02. No significant difference in the rest of the parameters for all study groups. CONCLUSIONS: Oxidation/antioxidation balance during chronic ischemic heart disease can be considered as a good metabolic ischemia indicator, that used in the monitoring and therapeutic evaluation could detect molecular changes that anticipate installation of tissue damage.

Adult↗
PubMed2006

Alzheimer's disease pathogenesis: role of aging.

Alzheimer's disease (AD) is the chief cause of dementia, and age is its major risk factor. The majority of cases (90-95%) are sporadic (SAD), and the remainder are familial (FAD). AD is characterized by two brain lesions, intraneuronal fibrillary tangles and extracellular plaques. The lesions are identical in SAD and FAD as well as to those in persons with Down's syndrome (DS). The same lesions are also observed frequently in elderly non-demented individuals (E-ND). Both AD lesions may stem from the normal progressive increases in oxidative stress (OxS) throughout the body with age. Onset of dementia due to the accumulating lesions is around 40 years for DS, 40-60 years for FAD, over about 65 years for SAD, while that for E-ND is unknown. The lesions are made clinically manifest with time by the normal increase with age of OxS, "the dementia of old age," or by a process specific for each AD category, which enhances the normal OxS so as to lower the unknown onset age of dementia for E-ND individuals to that associated with the AD category. A plausible process can be advanced for each AD category. The hypothesis suggests convenient, effective measures to prevent and treat, for example, by decreasing brain OxS levels with oral antioxidants such as lipoic or dehydroascorbic acids that are capable of passing the blood-brain barrier.

Aging↗
PubMed2001

Glucose transporter type 1 deficiency syndrome (Glut1DS): methylxanthines potentiate GLUT1 haploinsufficiency in vitro.

Methylxanthines such as caffeine and theophylline are known to inhibit glucose transport. We have studied such inhibition in the glucose transporter type 1 deficiency syndrome (Glut1DS) by erythrocyte glucose transport assays. Data from four patients with individual mutations in the GLUT1 gene are discussed: patient 1 (hemizygosity), 3 (S66F), 15 (368Ins23), and 17 (R333W). Zero-trans influx of (14)C-labeled 3-O-methyl glucose (3-OMG) into erythrocytes of patients is reduced (patient 1, 51%; 3, 45%; 15, 31%; 17, 52%) compared with maternal controls. Inhibition studies on patients 1, 3, 17, and maternal controls show an IC(50) for caffeine of approximately 1.5 mM both in controls (n = 3) and patients (n = 3) at 5 mM 3-OMG concentration. In the same two groups, kinetic studies show that 3 mM caffeine significantly decreases V(max) (p < 0.005), whereas the decrease in K(m) is significant (p < 0.01) only in the three controls and one patient (patient 3). Kinetic data from individual patients permit us to speculate that the interactions between caffeine and Glut1 are influenced by the mutation. Three mM caffeine also inhibits the transport of dehydroascorbic acid (DHA), another substrate for Glut1. The combined effects of caffeine (3 mM) and phenobarbital (10 mM) on glucose transport, as determined in patient 15 and the maternal control, show no additive or synergistic inhibition. These data indicate that caffeine and phenobarbital have similar Glut1 inhibitory properties in these two subjects. Our study suggests that Glut1DS patients may have a reduced safety margin for methylxanthines. Consumption of methylxanthine-containing products may aggravate the neurologic symptoms associated with the Glut1DS.

3-O-Methylglucose↗
PubMedDate not supplied

ESR investigations on the modification of the ascorbic acid-erythrocyte interaction by ferrous ions.

An ascorbic acid-erythrocyte interaction results in the formation of the semidehydroascorbate (SDA) radical and an increase in spin concentration. Addition of a more than ten-fold concentration of Fe2+ (as FeSO4) to such a system compensates the effect produced by ascorbic acid, that is the electron spin resonance spectrum obtained resembles very closely that of erythrocytes only. With the disappearance of the SDA radical a high spin ferric ion signal appears concomitantly at g = 4.3.

Ascorbic Acid↗
PubMedDate not supplied

The effect of alcohol oxidase on the ascorbic acid-erythrocyte interaction: ESR investigations.

Addition of alcohol oxidase to erythrocytes treated with ascorbic acid reverses the vitamin C effect, as expressed by the appearance of the semidehydroascorbate signal, and the increase in spin concentration. The original erythrocyte electron spin resonance (ESR) signal is, however, never restored completely, as it is in the case if ascorbate oxidase is used. Additional interaction between the enzyme alcohol oxidase and haemoglobin iron must occur, since both of the iron ESR signals at g = 4.3 and g = 6 disappear and the erythrocyte ESR spectrum at g approximately equal to 2 is changed characteristically. The spin concentration of the latter spectrum increases again above a certain concentration of alcohol oxidase.

Alcohol Oxidoreductases↗
PubMed1994

Efficacy of magnesium-L-ascorbyl-2-phosphate as a vitamin C source for weanling and growing-finishing swine.

Two experiments were conducted, one with weanling pigs (n = 288) and the second with grower-finisher swine (n = 216), to evaluate the efficacy of dietary vitamin C on various performance and serum measurements. Magnesium-L-ascorbyl-2-phosphate (46% L-ascorbic acid) served as the vitamin C source and was incorporated at dietary levels of 0, 50, or 500 ppm in both experiments. Pigs were allotted by sex, weight, and litter to randomized complete block designs. The nursery trial was conducted at four time periods and contained 12 replicates, whereas the grower-finisher experiment was over four time periods and contained nine replicates. Blood samples were collected initially from nine randomly selected pigs in both experiments, and from each pig within each pen at 2 and 5 wk postweaning, and at the 4- and 8-wk period in the grower-finisher trial. A killed Salmonella typhinurium bacterin was injected i.m. into starter pigs at 2 wk postweaning and at wk 4 and 6 in grower-finisher pigs. Hemagglutination titers were evaluated at 5 wk with the nursery pigs and at the 8-wk period with the grower-finisher swine. At the end of the grower-finisher trial, liver and kidney tissue were analyzed for ascorbate. Starter pigs grew faster (P < .05) and had improved gain:feed ratios (P < .05) when vitamin C was provided during the first 2 wk postweaning, but not during the latter 3-wk period. There was no improvement in pig gain or feed efficiency to vitamin C supplementation during any phase of the grower-finisher period.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMedDate not supplied

Determination of total vitamin C in fruit juices and related products by liquid chromatography: interlaboratory study.

A interlaboratory study was conducted to evaluate a liquid chromatographic (LC) procedure for the determination of total vitamin C in foods at levels of 5-60 mg/100 g. Emphasis was placed on fruit juices, although selected foods were also included in the study. Following dissolution of sample in water, endogenous dehydroascorbic acid was converted to ascorbic acid by precolumn reduction with dithiothreitol at neutral pH. Total ascorbate was determined by C18 reversed-phase LC with a phosphate eluent at pH 2.5, incorporating dithiothreitol to maintain vitamin C in the reduced form, and UV detection at 254 nm. Seven types of fruit juices and foods were tested by 19 collaborators in 7 countries. Three duplicate juices and foods met the criteria for Youden pairs and yielded repeatability relative standard deviation of 5.80-14.66%. Reproducibility relative standard deviation ranged from 6.36 to 35.54% (n = 10) with HORRAT values of 0.82-4.04. The LC method is suitable for routine use in fruit products and foods containing > 5 mg/100 g vitamin C and is recommended for further validation by AOAC INTERNATIONAL and International Fruit Juice Union.

Ascorbic Acid↗
PubMedDate not supplied

Effect of imipramine treatment on plasma dopamine beta-hydroxylase activity in chronic mild stress in rats.

Dopamine beta-hydroxylase (DBH) which catalyzes conversion of dopamine into noradrenaline, may be a good blood marker of unipolar depression. Therefore, we studied the effect of classic antidepressant drug imipramine (10 mg/kg ip) on activity of this enzyme in plasma of rats subjected to chronic mild stress (CMS), the model of anhedonia. CMS induced reductions in DBH activity by the second day and 5th week of stress duration. Imipramine treatment minimized these CMS-induced reductions. The data indicate that, similarly to human depression, CMS also affects DBH activity, and, moreover, the CMS-induced alterations are normalized by imipramine treatment.

Animals↗
PubMed1989

Development of a high-performance liquid chromatographic-post-column fluorogenic assay for digoxin in serum.

A quantitative, sensitive and specific assay for digoxin was developed using a high-performance liquid chromatographic (HPLC) system with post-column (PC) fluorogenic derivatization. Separation of digoxin from its metabolites was accomplished using a 15 cm X 4.6 mm I.D., 3-microns octadecylsilyl HPLC column and an optimum mobile phase of methanol-ethanol-isopropanol-dehydroascorbic acid (52:3:1:45, v/v). Concentrated hydrochloric acid, used as the PC derivatization reagent, was delivered by hexane displacement from a polyvinyl chloride pressure vessel. Construction of the pressure vessel is described. The mixture of HPLC effluent and PC reagent was passed into a 20-m knitted reactor (PTFE tubing) maintained at 79.0 +/- 0.2 degrees C. The resultant fluorophores were monitored by a fluorescence detector equipped with a 360-nm excitation filter and a 425-nm emission filter. Specificity of this HPLC-PC assay for digoxin in the presence of its metabolites was demonstrated. Also, numerous steroids evaluated did not produce fluorescence under these conditions. An extraction procedure for evaluating digoxin in serum without interference from endogenous compounds was also developed. Detector response to digoxin was linear from 0.5 to 3.3 ng extracted from serum.

Chromatography, High Pressure Liquid↗