title: 3-nitropropionic acid inhibition of succinate dehydrogenase (complex II) activity in cultured Chinese hamster ovary cells: antagonism by L-carnitine.
abstract: 3-Nitropropionic acid (3-NPA) is an inhibitor of the mitochondrial enzyme succinate dehydrogenase (SDH, a part of complex II) that links the tricarboxylic acid (TCA) cycle to the respiratory electron transport chain. 3-NPA inactivates SDH by covalently and irreversibly binding to its active site. We previously examined the effects of 3-NPA on the histochemical activity of SDH in vivo, by using the reduction of a yellow tetrazolium dye (nitro blue tetrazolium) to a blue formazan as an indicator. In studies of cultured cells, the related dye methylthiazoletetrazolium (MTT) has commonly been used as an indicator of the presence and number of viable cells; that is cells that are capable of producing energy via the TCA cycle. Here we observed that doses of 3-NPA as low as 10(-8) M inhibited formazan production in an in vitro model system using CHO cells. This effect was antagonized by l-carnitine, which greatly increased the production of formazan, indicating a considerable improvement in energy production by the cultured cells. CHO cells appear to be a convenient model for the evaluation of therapeutic compounds that may modulate cellular bioenergetics.
authors.affiliation: Laboratory of Experimental Neuropathology, Division of Neurotoxicology, National Center for Toxicological Research, USFDA, Arkansas 72079, USA. AScallet@nctr.fda.gov
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Scallet
authors.forename: Raney L
authors.initials: RL
authors.lastname: Haley
authors.forename: Dori M
authors.initials: DM
authors.lastname: Scallet
authors.forename: Helen M
authors.initials: HM
authors.lastname: Duhart
authors.forename: Zbigniew K
authors.initials: ZK
authors.lastname: Binienda
mesh_terms: D000818:Animals; D016466:CHO Cells; D002331:Carnitine / Q000378:metabolism / Q000494:pharmacology*; D019069:Cell Respiration / Q000187:drug effects; D004396:Coloring Agents / Q000378:metabolism; D006224:Cricetinae; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005562:Formazans / Q000378:metabolism; D018696:Neuroprotective Agents / Q000378:metabolism / Q000494:pharmacology; D009574:Nitro Compounds; D010084:Oxidation-Reduction; D011422:Propionates / Q000378:metabolism / Q000494:pharmacology*; D013385:Succinate Dehydrogenase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism
chemical_list: D004396:Coloring Agents; D004791:Enzyme Inhibitors; D005562:Formazans; D018696:Neuroprotective Agents; D009574:Nitro Compounds; D011422:Propionates; D013778:Tetrazolium Salts; D013844:Thiazoles; C079782:MTT formazan; D013385:Succinate Dehydrogenase; C022616:thiazolyl blue; C015392:3-nitropropionic acid; D002331:Carnitine