Comparative hepatotoxicity of two polychlorotrifluoroethylenes (3.1 oils) and two chlorotrifluoroethylene (CTFE) oligomers in male Fischer 344 rats

Chlorotrifluoroethylene trimer and tetramer are inducers of the CYP4A subfamily

Male Wistar albino rats were treated for a 7 day period with equimolar doses of the trimer and tetramer oligomers of chlorotrifluoroethylene (CTFE), resulting in significant hepatomegaly for both compounds. In addition, both trimer and tetramer significantly induced the peroxisomal beta-oxidation of fatty acids as assessed by increases in palmitoyl-coenzyme A (CoA) oxidation, thus confirming these oligomers as peroxisome proliferators. Consistent with these conclusions, both trimer and tetramer increased the hydroxylation of lauric acid indicating that the CTFEs were inducers of the CYP4A subfamily, a conclusion further supported by substantial increases in the steady-state levels of the cognate CYP4A1 mRNA as determined by northern blotting. The liver appeared to be more susceptible to induction than the kidney and the CTFE tetramer was more potent than the trimer. These results are discussed with respect to both the differential hepatotoxicity, and biotransformation/disposition of the two polyhalogenated oligomers.

In vitro methodologies for enhanced toxicity testing

This report will give a general overview of some of the in vitro methodologies used in toxicity testing. The use of computer-based structure-activity relationships and cell culture testing systems can provide valuable toxicological data for hazard and risk assessments. In vitro systems allow for a more rapid identification of toxic compounds and can be utilized to study mechanisms of toxicity at the cellular and subcellular level. The data derived from these types of studies can be used to improve the predictability of animal models for chemical or drug toxicity. This report focused on primary hepatocytes as an in vitro model for cytotoxicity and metabolic studies.

Evidence of hepatic conversion of C6 and C8 chlorotrifluoroethylene (CTFE) oligomers to their corresponding CTFE acids

The toxicity of polychlorotrifluoroethylene oil (3.1 oil) hydraulic fluid is believed to be related to the conversion of neutral chlorotrifluoroethylene (CTFE) oligomers to their corresponding halogenated fatty acids. Male Fischer-344 rats were orally gavaged (1.25 g/kg/d) with two batch formulated 3.1 oils (3.1 oil-C6 and 3.1 oil-C6:C8) and C6 CTFE (trimer) and C8 CTFE (tetramer) oligomers, respectively. All rats exposed to test compounds for 7 days demonstrated significant 2-fold increases in liver weight over controls. After 24-h and 7-day dosings, the amount of tetramer acid formed in the liver was 2x and 11x the amount of trimer acid formed, respectively. In addition to the formation of tetramer acid, rats dosed with tetramer also indicated comparable amounts of trimer acid. These data indicate that toxicity induced by the 3.1 oil may be due to the retention of the tetramer and the resulting persistent high concentrations of halogenated fatty acids.