Tetrachloroethane, pentachloroethane, and hexachloroethane: genetic and biochemical studies

Area of Science:

• Toxicology
• Genetics
• Biochemistry

Background:

• Halogenated hydrocarbons are environmental contaminants.
• Assessing their genotoxic and toxic effects is crucial for risk assessment.

Purpose of the Study:

• To evaluate the genotoxicity of tetrachloroethane (TTCE), pentachloroethane (PCE), and hexachloroethane (HCE) in yeast.
• To investigate the in vivo toxic effects of these compounds on mouse liver enzymes.

Main Methods:

• Yeast Saccharomyces cerevisiae (strain D7) was used in suspension tests with and without metabolic activation (S9).
• Mitotic gene conversion and point reverse mutation assays were performed.
• In vivo toxicity was assessed by measuring cytochrome P450 (cyt. P450) content and the activities of pentoxyresorufin O-dealkylase (PROD) and ethoxy-resorufin O-deethylase (EROD) in mouse hepatic microsomes.

Main Results:

• TTCE, PCE, and HCE induced genotoxicity in yeast cells from the logarithmic growth phase.
• PCE also caused significant gene conversion and mutation in stationary phase cells with S9 activation.
• Acute intoxication in mice led to marked decreases in cyt. P450, EROD, and PROD activities, with TTCE and PCE showing preferential effects on P448 forms.

Conclusions:

• TTCE, PCE, and HCE exhibit genotoxic potential.
• These compounds induce significant toxicity in vivo, impacting key drug-metabolizing enzyme systems.
• The results highlight the need for further investigation into the specific mechanisms of toxicity for these halogenated hydrocarbons.