title: Biochemical evidence that high concentrations of the antidepressant amoxapine may cause inhibition of mitochondrial electron transport.
abstract: Overdosage with the antidepressant amoxapine causes metabolic acidosis and may lead to brain damage and death. To better understand the metabolic disturbances caused by amoxapine overdose, its effects on three simple systems were studied: growth of Saccharomyces cerevisiae, mitochondrial energy metabolism, and an electron transport system in microsomal membranes. Growth of yeast on all substrates except lactate was inhibited by amoxapine at 50-100 micrograms ml-1. Growth on lactate was observed at 200 micrograms ml-1 of amoxapine. In beef heart mitochondria, amoxapine at 100 micrograms ml-1 inhibited reactions involving large sections of the electron transport chain. Energy-linked reactions in submitochondrial particles were also inhibited. Electron microscopy showed some disruption of the mitochondrial internal structure by amoxapine and a change from orthodox to condensed conformation. Microsomal NADH-cytochrome b5 reductase was inhibited by amoxapine, but at higher amoxapine concentrations than mitochondrial reactions. The results suggest amoxapine disrupts reactions of membrane-associated enzyme complexes, and mitochondrial energy conservation may be one of the first systems affected. We speculate that lactic acid accumulation in patients with amoxapine overdose may be caused by loss of electron acceptor activity in tissues.
authors.affiliation: Department of Biochemistry, University of Auckland, New Zealand.
authors.forename: A M
authors.initials: AM
authors.lastname: Roberton
authors.forename: L R
authors.initials: LR
authors.lastname: Ferguson
authors.forename: G J
authors.initials: GJ
authors.lastname: Cooper
mesh_terms: D000657:Amoxapine / Q000633:toxicity*; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects; D003989:Dibenzoxazepines / Q000633:toxicity*; D004579:Electron Transport / Q000187:drug effects*; D066298:In Vitro Techniques; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D009243:NAD / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects
chemical_list: D003989:Dibenzoxazepines; D007773:Lactates; D009243:NAD; D019344:Lactic Acid; D000657:Amoxapine