1,1,1-TRIFLUORO-2,2-DICHLOROETHANE (HCFC-123) AND 1,1,1-TRIFLUORO-2-BROMO-2-CHLOROETHANE (HALOTHANE) CAUSE SIMILAR BIOCHEMICAL EFFECTS IN RATS EXPOSED BY INHALATION FOR 5 DAYS

1,1,1-Trifluoro-2,2-dichloroethane (HCFC-123) and 1,1,1-trifluoro-2 -b romo-2 chloroethane (halothane) are gases with anesthetic properties. HCFC-123 is used as a refrigerant, fire extinguishing agent, and solve nt, while halothane is a clinical anesthetic. Much information is avai lable on chronic toxicity of HCFC-123 in animals, while the informatio n available for halothane is from short-term animal exposures or chron ic, low level human exposures. Thus, there is little biochemical infor mation available on similar endpoints for these two chemicals, which s hare common metabolites. In the present study, male rats were exposed to 5000 ppm HCFC-123, 5000 ppm halothane, or room air for 6 hr per day for 5 consecutive days. Bats exposed to both test compounds gained li ttle or no weight during the study. Liver weights were slightly decrea sed in the rats exposed to HCFC-123 and halothane compared to controls . The serum triglycerides were decreased to approximately 20% of contr ol level in rats exposed to both HCFC-123 and halothane, and serum cho lesterol was decreased to less than 80% of control by both compounds. Both test compounds increased hepatic beta -oxidation by approximately 3-fold over control, and HCFC-123 caused a significant increase in he patic cytochrome P450 content, while the increase in cytochrome P450 w as not statistically significant in the halothane-treated rats. The re sults indicate that HCFC-123 and halothane share not only common metab olic pathways, but also several common biological effects, specificall y those associated with peroxisome proliferation. These data indicate that human experience with halothane may be useful in the risk assessm ent of HCFC-123.