The effect of L-ascorbic acid and/or tocopherol supplementation on electrophysiological parameters of the colon of rats chronically exposed to lead.

BACKGROUND: The aim of this study was to assess the effect of diet supplementation with L-ascorbic acid (500 mg/L), tocopherol (3 mg/kg b.w.), and/or a water soluble analog of tocopherol (Trolox) (48 mg/L) on ion transport in the colon of rats subjected to a chronic exposure (9 months) to 0.1% lead acetate in drinking water. MATERIAL/METHODS: The electrophysiological parameters of the colon wall were measured with Ussing methods. Lead content in the whole blood was analyzed by graphite furnace atomic absorption spectrometry (GFAAS) using Zeeman correction. L-ascorbic acid and tocopherol in plasma was measured by high performance liquid chromatography. Immunohistochemical reaction was carried out for visualization of occludin, the intracellular tight junction protein. RESULTS: We showed a strong inhibitory effect of lead on the electrophysiological parameters, changes in intestinal permeability, disappearance of junctional occludin, decreased amount of mucus covering the colon surface, and the accumulation of PAS-positive substance in the apical region of the cytoplasm in the absorptive cells. CONCLUSIONS: Supplementation with tocopherol or Trolox did not exert a beneficial influence on the studied parameters. L-ascorbic acid positively influenced the examined electrophysiological parameters, as it cancelled the inhibitory influence of lead on ion transport in the rat colon. L-ascorbic acid also protected against tight junction disruption of epithelial cells in the colon of the lead-treated rats. A similar effect was observed in the group of rats receiving lead and supplemented with L-ascorbic acid plus Trolox.

[Oxidative stress and trace elements affect the activity of sodium transporting systems in a cellular membrane of a erythrocyte]. / Stres oksydacyjny i pierwiastki sladowe wplywaja na aktywnosc systemów transportujacych sód w blonie komórkowej erytrocytu.

We examined the activity of sodium transporting systems (STS) in a cellular membrane of erythrocytes in a group of 21 patients under chronic hemodialysis treatment with the dialyzing fluid containing glucose HD-g(+), and 22 patients dialysed with the fluid not containing glucose HD-g(-), 21 patients with chronic kidney failure already not treated with dialysis and 21 control group. We examined the concentration of antioxidative system cofactors, such as zinc, copper and selenium in erythrocytes and plasma. The marker of oxidative stress in erythrocytes and plasma was the concentration of TBARS. Among all STS we examined the activity of Na(+)/K(+) ATP-ase, Na(+)/K(+)/Cl(-); co-transport, Na(+)/Li(+) exchanger, Na(+), K(+)-outflow. Copper zinc and selenium as cofactors of antioxidative enzymes may reflect the antioxidative processes inside the organism undergoing the influence of free radicals.

Influence of glucose in the dialysate on the activity of erythrocyte-glutathione-peroxidase and blood selenium concentration in hemodialyzed patients.

BACKGROUND: The aim of the study was to show the influence of glucose in the dialysate on the intensity of oxidative stress, activity of glutathione peroxidase (GSHPx) and concentration of selenium in patients undergoing regular hemodialysis. METHODS: The study was comprised of 85 patients hemodialyzed with dialysate containing glucose [HD-g(+)] or not containing glucose [HD-g(-)], patients with chronic renal failure on conservative treatment and control group. The concentrations of the products of reaction with thiobarbituric acid (TBARS), concentration of selenium in erythrocytes and plasma, concentration of copper in erythrocytes and the activity of GSHPx were determined. RESULTS: GSHPx had significantly higher activity in HD-g(-) group before HD than in control group. In HD-g(+) group before hemodialysis, the activity of GSHPx was significantly lower than in the control group. After HD, the activity showed a statistically significant increase. In both hemodialyzed groups, selenium concentration before hemodialysis both in plasma and erythrocytes was significantly lower, compared to control group. In the group of patients with CRF on conservative treatment, selenium concentration in RBC was significantly higher, compared to concentrations obtained in other groups except for control group. The increase of copper concentration in erythrocytes was accompanied by the increase of oxidative stress and increase of TBARS concentration. The opposite relationship was observed for selenium-its concentration was inversely correlated to copper concentration. CONCLUSIONS: In both groups of hemodialyzed patients, hemodialysis caused the increase of GSHPx in erythrocyte activity and increase of plasma and erythrocyte selenium concentration.

Do trace elements modify the activity of erythrocyte sodium-proton exchanger in hemodialyzed patients?

The kinetics (Vmax and Km) of the erythrocyte Na+-H+ exchanger was studied in a group of 21 patients undergoing regular hemodialysis (HD) and in 21 control subjects. The activity of antioxidative enzymes--superoxide dismutase and glutathione peroxidase--as well as the concentrations of their cofactors--zinc, copper, and selenium--in plasma and in erythrocytes were determined. The thiobarbituric acid-reactive substances (TBARS) concentration served as an indicator of oxidative stress intensity in plasma and erythrocytes. It was found that in the control group the concentration of copper in erythrocytes was positively correlated with Km and Vmax. When the concentration of copper increased, the shape of the kinetic curve changed from sigmoidal to hyperbolic. In the control group, the concentration of zinc in erythrocytes also correlated with Km. However, the results obtained for the group of hemodialyzed patients were the opposite: when the erythrocyte concentration of copper increased, a Km decline was observed and the shape of the curve changed from hyperbolic to sigmoidal. In the group of hemodialyzed patients, we also found a positive correlation between Km and the concentration of selenium in erythrocytes, and a negative correlation between Km and erythrocyte TBARS.

[The effect of hemodialysis on some parameters of the antioxidant system in the blood of patients with chronic renal failure]. / Wplyw hemodializy na stan wybranych elementów ukladu krwi u pacjentów z przewlekla niewydolnoscia nerek.

UNLABELLED: Direct contact of the blood with the dialysis membrane during hemodialysis elicits a series of changes in blood cells. White blood cell count and total lymphocyte number are reduced, neutrocytes are stimulated and degranulate, platelet adhesiveness is enhanced. Interactions of granulocytes with the dialysis membrane stimulate the production of ROS and activate aerobic reactions triggering oxidative stress. Red blood cells form the "first line of defense" during contact of the blood with the dialysis membrane. The effect of ROS on erythrocytes appears in the form of reduced osmotic resistance of their cellular membrane and susceptibility to disintegration which results in the release of small quantities of hemoglobin and significant reduction in the lifetime of these cells. Oxidative stress caused by contact of the blood with the dialysis membrane triggers defense mechanisms in the erythrocyte that protect against oxidative damage. Reports on the effects of hemodialysis on the antioxidant system of the blood in patients with chronic renal failure are conflicting and the present work was aimed at resolving some of the discord. The following questions were addressed: (1) Does hemodialysis affect the antioxidant system of the blood in patients with chronic renal failure? (2) Are there associations between parameters of hemodialysis and of the blood's antioxidant system? (3) Is supplementation with antioxidants needed in hemodialysed patients? The experiments were done at the Department of Biochemistry and Chemistry, Pomeranian Medical University. Plasma and erythrocytes were obtained from 42 patients aged 67.7 +/- 12.3 years, treated at the Department of Nephrology, Transplantology and Internal Medicine, Pomeranian Medical University, due to chronic renal failure caused by chronic glomerulonephritis (n=16), pyelonephritis (n=12), diabetes (n=3), arterial hypertension (n=3) or other cause (gout, nephrolithiasis, n=8). The patients were assigned to two equal groups: 1--with end-stage renal failure on hemodialysis; 2--eated conservatively. Hemodialysis was done three times per week, 4 hours per session, using Fresenius dialysers with polysulfone membranes and bicarbonate buffer with glucose. The control group comprised 21 healthy volunteers. All groups were matched for age and gender. A 10 mL heparinized blood sample was collected twice from group 1 patients before and after dialysis directly from the dialysis catheter and once after an overnight fast from group 2 patients and controls. Glutathione concentration was determined in whole blood. Plasma was prepared by centrifugation and MDA, Se, Cu, Zn, and Fe levels were measured. SOD, GSH-Px, and CAT activities, MDA, Se, Cu, Zn, and Fe levels were determined in erythrocytes. Statistical methods were applied to determine significance of differences between groups and correlations between parameters studied. CONCLUSIONS: (1) Hemodialysis leads to significant changes in the antioxidant system of the blood of patients with chronic renal failure. The effect is noticeable with antioxidant enzyme activities and concentrations of nonenzymatic components of the system. (2) The activity of erythrocyte GSH-Px decreases with time of dialysis potentiating the effects of oxidative stress. (3) Reduced erythrocyte levels of Se in dialysed patients correlate with lower GSH-Px activities. Selenium supplementation may be of benefit to the antioxidative defense mechanisms.

Serum selenium level and glutathione peroxidase activity in steroid-sensitive nephrotic syndrome.

In our previous study the pattern of glutathione peroxidase (GPX) activity in the course of steroid-sensitive nephrotic syndrome (SSNS) in children suggested a defect in antioxidant defense. In the present report the serum selenium (Se) level, an essential component of GPX activity, was measured in a comparable group of children with SSNS at the same clinical stages at which GPX activity was determined in the previous study. Nephrotic children had normal serum Se levels during the edematous stage, at the end of prednisone treatment, and in remission. At the end of high-dose prednisone treatment, the serum Se level increased ( P<0.01) simultaneously with enhanced activity of GPX. These results suggest that children with SSNS have a persistent defect in the antioxidant defense at the important stage of hydrogen peroxide and fatty acid hydroperoxide decomposition. This defect is transiently alleviated by high-dose prednisone treatment.