Demonstration of halothane-induced hepatic lipid peroxidation in rats by quantification of F2-isoprostanes.
BACKGROUND
Halothane can be reductively metabolized to free radical intermediates that may initiate lipid peroxidation. Hypoxia and phenobarbital pretreatment in Sprague-Dawley rats increases reductive metabolism of halothane. F(2)-isoprostanes, a novel measure of lipid peroxidation in vivo, were used to quantify halothane-induced lipid peroxidation in rats.


METHODS
Rats were exposed to 1% halothane or 14% O(2) for 2 h. Pretreatments included phenobarbital, isoniazid, or vehicle. Rats also were exposed to halothane, enflurane, and desflurane at 21% O(2). Lipid peroxidation was assessed by mass spectrometric quantification of F(2)-isoprostanes.


RESULTS
Exposure of phenobarbital-pretreated rats to 1% halothane at 21% O(2) for 2 h caused liver and plasma F(2)-isoprostane concentrations to increase fivefold compared to nonhalothane control rats. This halothane-induced increase was enhanced by 14% O(2), but hypoxia alone had no significant effect. Alanine aminotransferase activity at 24 h was significantly increased only in the 1% halothane/14% O(2) group. The effect of cytochrome P450 enzyme induction on halothane-induced F(2)-isoprostane production and liver injury was determined by comparing the effects of isoniazid and phenobarbital pretreatment with no pretreatment under hypoxic conditions. Halothane caused 4- and 11-fold increases in plasma and liver F(2)-isoprostanes, respectively, in non-pretreated rats, whereas isoniazid pretreatment had no effect. Phenobarbital pretreatment potentiated halothane-induced lipid peroxidation with 9- and 20-fold increases in plasma and liver F(2)-isoprostanes, respectively. Alanine aminotransferase activity was increased only in this group. At ambient oxygen concentrations, halothane but not enflurane or desflurane, caused F(2)-isoprostanes to increase.


CONCLUSIONS
Specific halothane-induced lipid peroxidation was demonstrated in Sprague-Dawley rats using quantification of F(2)-isoprostanes and was increased by hypoxia and phenobarbital pretreatment, but not isoniazid pretreatment.
Awad
J A
JA
Department of Anesthesiology, Vanderbilt University, Nashville, Tennessee 37232, USA.
Horn
J L
JL
Roberts
L J
LJ
Franks
J J
JJ
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D015237:Dinoprost / Q000096:biosynthesis*; D006221:Halothane / Q000494:pharmacology*; D007538:Isoniazid / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects*; D008099:Liver / Q000378:metabolism*; D008297:Male; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D018685:Anesthetics, Inhalation; D015237:Dinoprost; D006221:Halothane; D007538:Isoniazid; D010634:Phenobarbital