title: Quantitative and mechanistic aspects of the hydroperoxide-induced release of Ca2+ from rat liver mitochondria.
abstract: We have previously demonstrated in rat liver mitochondria a hydroperoxide-induced hydrolysis of pyridine nucleotides and release of Ca2+ [Lötscher, H. R., Winterhalter, K. H., Carafoli, E. & Richter, C. (1979) Proc. Natl Acad. Sci. USA 76, 4340-4344, and Lötscher, H. R., Winterhalter, K. H., Carafoli, E. & Richter, C. (1980) J. Biol. Chem. 255, 9325-9330]. Here we investigate pyridine nucleotide hydrolysis and Ca2+ release under conditions of minimized Ca2+ cycling and with smaller Ca2+ loads. The extent of pyridine nucleotide hydrolysis, measured by pyridine-nucleotide-derived nicotinamide release from intact mitochondria, and the Ca2+ release rate show a very similar sigmoidal dependence on the mitochondrial Ca2+ load. The hydrolysis of oxidized pyridine nucleotides is limited under non-cycling conditions. Whereas pyridine nucleotide hydrolysis as measured by nicotinamide release is extensive, net loss of mitochondrial pyridine nucleotides is observed only at relatively high Ca2+ loads. Our results indicate the ability of mitochondria to resynthesize pyridine nucleotides after hydrolysis. Neither a decrease of reduced, nor an increase of oxidized, mitochondrial glutathione favour Ca2+ release. From these and previous findings it is concluded that the hydroperoxide-induced Ca2+ release is triggered by a factor which is distal to the oxidation of mitochondrial pyridine nucleotides. Ca2+ release is stimulated when the movement of protons across the inner mitochondrial membrane is facilitated, giving evidence for the operation of the hydroperoxide-induced release pathway as a Ca2+/H+ antiport.
authors.forename: B
authors.initials: B
authors.lastname: Frei
authors.forename: K H
authors.initials: KH
authors.lastname: Winterhalter
authors.forename: C
authors.initials: C
authors.lastname: Richter
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D005260:Female; D005978:Glutathione / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D006868:Hydrolysis; D066298:In Vitro Techniques; D008930:Mitochondria, Liver / Q000201:enzymology / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009536:Niacinamide / Q000378:metabolism; D010084:Oxidation-Reduction; D010545:Peroxides / Q000378:metabolism*; D011522:Protons; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D010545:Peroxides; D011522:Protons; D009243:NAD; D009536:Niacinamide; D009249:NADP; D005980:Glutathione Reductase; D005978:Glutathione; D002118:Calcium