Lonidamine-mediated respiratory changes in rat heart myocytes: a re-examination of the functional response of mitochondrial cytochrome c oxidase.
Respiratory activity of intact cardiac myocytes isolated from rats treated with lonidamine (LND) has been examined under conditions where cytochrome oxidase turns over at its maximal rate. Compared to myocytes isolated from control rat hearts, those treated with LND displayed a 60% increase in the cytochrome oxidase-dependent rate of respiration; electron microscopy revealed, in agreement with the literature, that the membrane structure of the mitochondrion had become disorganized. The increase in the rate of oxygen consumption was correlated with the (partial) impairment of the membrane ability to maintain the proton electrochemical potential gradient which normally inhibits oxidase activity. Results are discussed with reference to previous reports showing no effect of LND on cytochrome c oxidase activity. The evidence reported better clarifies the contribution of cytochrome oxidase to the demonstrated energetic failure displayed by cells treated with LND.
Department of Biochemical Sciences, University of Rome La Sapienza, Italy.
P
P
Sarti
G
G
Antonini
G
G
Arancia
T J
TJ
Blanck
G
G
Citro
A
A
Meloni
A
A
Molinari
F
F
Malatesta
D000818:Animals; D002478:Cells, Cultured; D003576:Electron Transport Complex IV / Q000378:metabolism*; D007191:Indazoles / Q000494:pharmacology*; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000201:enzymology / Q000648:ultrastructure; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
D007191:Indazoles; D003576:Electron Transport Complex IV; C016371:lonidamine