ENHANCED NO PRODUCTION DURING MG DEFICIENCY AND ITS ROLE IN MEDIATINGRED-BLOOD-CELL GLUTATHIONE LOSS

The effect of dietary Mg deficiency on nitric oxide (NO) production an d its role in mediating oxidative depletion of red blood cell (RBC) gl utathione in rats were investigated. Male Sprague-Dawley rats were pla ced on Mg-deficient or Mg-sufficient diets for up to 3 wk. Plasma nitr ate plus nitrite levels, determined by the Escherichia coli reductase/ Griess reagent procedures, increased 1.7-fold during the 1st wk and in creased 2- to 2.4-fold during the 2nd and 3rd wk on the Mg-deficient d iet. In association, substantial losses (similar to 50%) of RBC glutat hione occurred during the 2nd and 3rd wk. Administration of the NO syn thesis inhibitor N-G-nitro-L-arginine methyl ester (L-NAME) in drinkin g water (0.5 mg/ml) effectively blunted the increases in plasma nitrat e/nitrite nitrite during Mg deficiency. Concomitantly, losses of RBC g lutathione exhibited by Mg-deficient rats were significantly attenuate d. 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 isolat ed RBCs, losses of the glutathione could be induced directly by peroxy nitrite or 3-morpholinosydnonimine, which generates NO + . O-2(-), but not by NO (from sodium nitroprusside) alone, in a concentration-depen dent manner. The results clearly indicate that NO overproduction occur s and participates in RBC glutathione loss during Mg deficiency. Becau se neutrophil activation also occurs, we suggest that NO might interac t with superoxide anions to form peroxynitrite, which then directly ox idizes RBC glutathione.