Effects of rotenone and pyridaben on complex i electron transfer and on mitochondrial nitric oxide synthase functional activity

NAVARRO, ANA; BÁNDEZ, MANUEL; GOMEZ, CARMEN; SANCHEZ PINO, MARIA; REPETTO, MARISA; BOVERIS, A.

JOURNAL OF BIOENERGETICS AND BIOMEMBRANES

SPRINGER/PLENUM PUBLISHERS

Lugar: New York; Año: 2010 vol. 42 p. 405 - 412

0145-479X

Rotenone and pyridaben, both inhibitors of mitochondrial complex I, were assayed in brain mitochondria and mitochondrial fragments determining Ki (the inhibitor concentration that produces half maximal inhibition) and Imax (% of inhibition at maximal inhibitor concentration) in: the activities of complexes I, II and IV; the respiration rates in states 3, 3u (uncoupled) and 4 with malate-glutamate and succinate as substrates; the biochemical and functional activities of mitochondrial nitric oxide synthase (mtNOS); and inner membrane potential by rhodamine 123 fluorescence). Results indicate a selective inhibition of complex I activity, of mitochondrial respiration and of membrane potential with malate-glutamate as substrate, with a Ki (expressed as the stochiometric ratio) of 0.28-0.36 nmol inhibitor/mg of mitochondrial protein. Functional mtNOS activity was half-inhibited at 0.70-0.74 nmol inhibitor/mg protein in state 3 mitochondria, interpreted as indication of a structural interaction between complex I and mtNOS, and at 2.52-2.98 nmol inhibitor/mg protein in uncoupled (state 3u) mitochondria, interpreted as indication of a weaker complex I-mtNOS structural interaction in state 3u. Results are considered in terms of the solid sate model of the mitochondrial respiratory chain with mtNOS adjacent to complex I and with an intermolecular non covalent bonding between complex I and mtNOS that is stronger at high values.