Absence of stereospecific effects of bupivacaine isomers on heart mitochondrial bioenergetics.
BACKGROUND
Highly lipophilic local anesthetics interfere with mitochondrial energy metabolism. These metabolic effects could, in part, explain some toxic effects of local anesthetics, such as bupivacaine-induced myocardial depression. The purpose of this study was to compare the optically pure isomers of bupivacaine on heart mitochondrial bioenergetics.


METHODS
Both bupivacaine enantiomers were tested on rat heart isolated mitochondria. Oxygen consumption, adenosine triphosphate synthesis, and enzymatic activities of the four complexes of the respiratory chain were measured.


RESULTS
No significant differences were found between R(+)- and S(-)-bupivacaine on mitochondrial oxidative phosphorylation with a similar dose-dependent decrease in adenosine triphosphate synthesis. Complex I (nicotinamide adenine dinucleotide ubiquinone reductase) was the enzymatic complex of the respiratory chain most sensitive to the bupivacaine isomers. Half-inhibitory concentrations for R(+)- and S(-)-bupivacaine were not statistically different (3.3 +/- 0.4 mm and 2.8 +/- 0.6 mm, respectively).


CONCLUSIONS
No stereospecific effects of bupivacaine enantiomers were shown in the inhibition of complex I activity and uncoupling of oxidative phosphorylation. This can be correlated with the lack of stereospecific effects of bupivacaine on myocardial depression. The lipid solubility of local anesthetics appears to be the principal physicochemical factor affecting the potency of these tertiary amines on mitochondrial bioenergetics.
Sztark
F
F
Laboratoire d'Anesthésiologie (INSERM EMI 9929), Université Victor Segalen Bordeaux 2, France. sztark@u-bordeaux2.fr
Nouette-Gaulain
K
K
Malgat
M
M
Dabadie
P
P
Mazat
J P
JP
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D002045:Bupivacaine / Q000494:pharmacology*; D004579:Electron Transport / Q000187:drug effects; D004734:Energy Metabolism / Q000187:drug effects*; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013237:Stereoisomerism
D000779:Anesthetics, Local; D000255:Adenosine Triphosphate; D002045:Bupivacaine