title: Quinone imine-induced Ca2+ release from isolated rat liver mitochondria.
abstract: Incubation of Ca2(+)-loaded rat liver mitochondria with N-acetyl-p-benzoquinone imine (NAPQI) or its two dimethylated analogues resulted in a concentration dependent Ca2+ release, with the following order of potency: 2,6-(Me)2-NAPQI greater than NAPQI greater than 3,5-(Me)2-NAPQI. The quinone imine-induced Ca2+ release was associated with NAD(P)H oxidation and was prevented when NAD(P)+ reduction was stimulated by the addition of 3-hydroxybutyrate. Mitochondrial glutathione was completely depleted within 0.5 min by all three quinone imines, even at low concentrations that did not result in Ca2+ release. Depletion of mitochondrial GSH by pretreatment with 1-chloro-2,4-dinitrobenzene enhanced quinone imine-induced NAD(P)H oxidation and Ca2+ release. However, 3-hydroxybutyrate protected from quinone imine-induced Ca2+ release in GSH-depleted mitochondria. Mitochondrial membrane potential was lost after the addition of quinone imines at concentrations that caused rapid Ca2+ release; however, subsequent addition of EGTA led to the complete recovery of the transmembrane potential. In the absence of Ca2+, the quinone imines caused only a small and transient loss of the transmembrane potential. Taken together, our results suggests that the quinone imine-induced Ca2+ release from mitochondria is a consequence of NAD(P)H oxidation rather than GSH depletion, GSSG formation, or mitochondrial inner membrane damage.
authors.affiliation: Department of Toxicology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Weis
authors.forename: G A
authors.initials: GA
authors.lastname: Moore
authors.forename: I A
authors.initials: IA
authors.lastname: Cotgreave
authors.forename: S D
authors.initials: SD
authors.lastname: Nelson
authors.forename: P
authors.initials: P
authors.lastname: Moldeus
mesh_terms: D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D005978:Glutathione / Q000502:physiology; D007097:Imines / Q000494:pharmacology*; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D009249:NADP / Q000502:physiology; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D016227:Benzoquinones; D007097:Imines; D013438:Sulfhydryl Compounds; D009249:NADP; C028473:N-acetyl-4-benzoquinoneimine; D005978:Glutathione; D002118:Calcium