Enhanced NO production during Mg deficiency and its role in mediating red blood cell glutathione loss

Abstract

The effect of dietary Mg deficiency on nitric oxide (NO) production and its role in mediating oxidative depletion of red blood cell (RBC) glutathione in rats were investigated. Male Sprague-Dawley rats were placed on Mg-deficient or Mg-sufficient diets for up to 3 wk. Plasma nitrate plus nitrite levels, determined by the Escherichia coli reductase/Griess reagent procedures, increased 1.7-fold during the 1st wk and increased 2- to 2.4-fold during the 2nd and 3rd wk on the Mg-deficient diet. In association, substantial losses (approximately 50%) of RBC glutathione occurred during the 2nd and 3rd wk. Administration of the NO synthesis inhibitor NG-nitro-L-arginine methyl ester (L-NAME) in drinking water (0.5 mg/ml) effectively blunted the increases in plasma nitrate/nitrite during Mg deficiency. Concomitantly, losses of RBC glutathione exhibited by Mg-deficient rats were significantly attenuated. Packed RBCs, obtained from Mg-deficient but not from Mg-sufficient animals, displayed a prominent nitrosyl hemoglobin signal detected by electron spin resonance spectroscopy; the signals of the samples from the L-NAME-treated Mg-deficient rats were greatly reduced. With isolated RBCs, losses of the glutathione could be induced directly by peroxynitrite or 3-morpholinosydnonimine, which generates NO + .O2-, but not by NO (from sodium nitroprusside) alone, in a concentration-dependent manner. The results clearly indicate that NO overproduction occurs and participates in RBC glutathione loss during Mg deficiency. Because neutrophil activation also occurs, we suggest that NO might interact with superoxide anions to form peroxynitrite, which then directly oxidizes RBC glutathione.

Mg supplementation attenuates ritonavir-induced hyperlipidemia, oxidative stress, and cardiac dysfunction in rats

“…Liver and cardiac samples were rapidly excised, processed, frozen, and stored at Ϫ80°C. Plasma Mg levels were determined by flame emission atomic absorption spectroscopy (AA) (31,34).…”

“…Plasma total cholesterol levels were determined by a fluorometric method using a Cayman's cholesterol assay kit (4), and total plasma cholesterol content was estimated on the basis of relative fluorescence obtained from standards using an excitation of 550 nm and emission of 590 nm. Plasma 8-isoprostane levels were determined by an enzyme immunoassay kit (Cayman Chemical, Ann Arbor, MI) (31,32,35), and RBC reduced (GSH) and oxidized (GSSG) glutathione levels were assessed enzymatically by the DTNB-GSSG reductase method (31,(33)(34)(35). Neutrophils from whole blood were isolated by a step-gradient centrifugation within 20 min after death, and both basal (no stimulus) and PMA-stimulated (by 125 ng/ml phorbol 12-myristate 13-acetate) superoxide productions were assayed as described previously (31,32,35).…”

N-Methyl-d-aspartate Receptor Blockade Inhibits Cardiac Inflammation in the Mg2+-Deficient Rat

“…The plasma samples were quickly frozen and stored at -70°C for later analysis of PGE 2 . Total RBC glutathione was determined by the enzymatic recycling method as described previously (Mak et al, 1994(Mak et al, , 1996. Red cell hemoglobin was determined by the cyanmethemyoglobin method using Sigma Diagnostics hemoglobin reagent.…”

Toward a broader understanding of aldosterone in congestive heart failure

“…74 Weglicki and co-workers have identified an early (week 1) induction of oxi/nitrosative stress and depletion of antioxidant defences in PBMC and endothelial cells. [75][76][77][78] The lymphocyte activation featured here includes their production of proinflammatory cytokines and a neurogenic peptide, substance P, together with the expression of its receptors. 79 Cardiac lesions first appear in this model during week 3 and can be prevented by a substance P receptor antagonist.…”