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 five days.

1,1,1-Trifluoro-2,2-dichloroethane (HCFC-123) and 1,1,1-trifluoro-2-bromo-2 chloroethane (halothane) are gases with anesthetic properties. HCFC-123 is used as a refrigerant, fire extinquishing agent, and solvent, while halothane is a clinical anesthetic. Much information is available on chronic toxicity of HCFC-123 in animals, while the information available for halothane is from short-term animal exposures or chronic, low level human exposures. Thus, there is little biochemical information available on similar endpoints for these two chemicals, which share 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. Rats exposed to both test compounds gained little or no weight during the study. Liver weights were slightly decreased in the rats exposed to HCFC-123 and halothane compared to controls. The serum triglycerides were decreased to approximately 20% of control level in rats exposed to both HCFC-123 and halothane, and serum cholesterol 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 hepatic cytochrome P450 content, while the increase in cytochrome P450 was not statistically significant in the halothane-treated rats. The results indicate that HCFC-123 and halothane share not only common metabolic pathways, but also several common biological effects, specifically those associated with peroxisome proliferation. These data indicate that human experience with halothane may be useful in the risk assessment of HCFC-123.