TIME-COURSE OF 72-KILODALTON HEAT-SHOCK PROTEIN INDUCTION AND APPEARANCE OF TRIFLUOROACETYL ADDUCTS IN LIVERS OF HALOTHANE-EXPOSED RATS

Previous studies have shown that exposure of phenobarbital-pretreated rats to halothane in 10% O-2 causes centrilobular necrosis, induces ex pression of the 72-kDa heat shock protein (HSP72), and produces severa l trifluoroacetylated adducts. In the present study the time course of development of the centrilobular lesion, as measured by histochemistr y, was compared with the time course of appearance of both trifluoroac etylated adducts and HSP72, as measured by Western blotting. One group of 20 rats was pretreated with phenobarbital for 5 days, whereas a se cond group of two rats was left as untreated controls. Ten phenobarbit al-pretreated rats were exposed for 2 hr to 1% halothane in 10% O-2 an d 10 were exposed to 1% halothane in 20% O-2. At either 2, 4, 6, or 24 hr after exposure, livers were excised and frozen without fixation. T hin sections stained with hematoxylin and eosin demonstrated that cent rilobular lesions occurred at 6 hr and became extensive at 24 hr in ra ts pretreated with phenobarbital and exposed to 1% halothane in 10% O- 2. The time course of appearance of both trifluoroacetylated adducts a nd HSP72 was determined by Western blotting. Trifluoroacetylated adduc ts appeared in all rats exposed to halothane by 2 hr, lasted until 6 h r, and then diminished by 24 hr. In contrast, HSP72 was induced only i n the rats pretreated with phenobarbital and exposed to 1% halothane i n 10% O-2. HSP72 appeared in both the nuclear and supernatant fraction s at 6 hr after exposure and was intense 24 hr after exposure.