title: Hydroperoxides can modulate the redox state of pyridine nucleotides and the calcium balance in rat liver mitochondria.
abstract: When rats are fed a selenium-deficient diet, the glutathione peroxidase activity in liver mitochondria decreases within 5 weeks to 0-6% of that of control animals fed on a diet supplemented with 0.5 ppm of selenium as sodium selenite. Analysis of the temperature dependence of energy-linked Ca(2+) uptake by means of Arrhenius plots reveals two breaks (at around 11 degrees C and 24 degrees C) in mitochondria isolated from selenium-supplemented animals, whereas in selenium-deficient rats the break at 11 degrees C is absent. Ca(2+)-loaded mitochondria of selenium-supplemented rats-i.e., with active glutathione peroxidase in the matrix-lose Ca(2+) rapidly, with a concomitant oxidation of endogenous NAD(P)H, when exposed to t-butyl hydroperoxide or H(2)O(2). In contrast, in selenium deficiency, t-butyl hydroperoxide and H(2)O(2) induce neither a release of Ca(2+) nor an oxidation of NAD(P)H. The peroxide-induced oxidation of NAD(P)H is reversible in the presence of succinate when no Ca(2+) has been taken up. When Ca(2+) has previously been accumulated, however, the oxidation of NAD(P)H is irreversible. Enzymatic analysis of mitochondrial pyridine nucleotides reveals that the peroxide-induced oxidation of NAD(P)H in Ca(2+)-loaded mitochondria leads to a loss of NAD(+) and NADP(+). It is proposed that the redox state of mitochondrial pyridine nucleotides can be or is in part controlled by glutathione peroxidase and glutathione reductase and is a factor in the balance of Ca(2+) between mitochondria and medium.
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000378:metabolism*; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D010545:Peroxides / Q000378:metabolism*; D051381:Rats; D012643:Selenium / Q000172:deficiency; D013696:Temperature
chemical_list: D010545:Peroxides; D009243:NAD; D009249:NADP; D010544:Peroxidases; D005979:Glutathione Peroxidase; D012643:Selenium; D002118:Calcium