Reduced mitochondrial membrane potential and metabolism correspond to acute chloroform toxicity of in vitro hepatocytes

Chloroform is a non‐genotoxic compound that is present in drinking water and ambient air as a result of water chlorination but whose carcinogenic mechanism in humans is unknown. Chloroform targets the liver in humans, where cytochrome P‐450‐dependent biotransformation to phosgene results in mitochondrial damage and cell death. The purpose of this study is to investigate the relationship between cell death, loss of mitochondrial membrane potential (MMP) and reduction of metabolic rates for in vitro cultured mouse hepatocytes after acute exposure to two doses of chloroform. Immediately following a 2‐h exposure, culture viabilities were 70% and 54% for concentrations of 7.0 and 8.8 mM, respectively, in contrast with 90.0% for controls. Interestingly, the viabilities of these cultures decreased further, to 6% and 12%, respectively, over the next 24‐h period despite being placed in fresh, chloroform‐free medium. Measurement of MMP for viable cells at the end of the exposure revealed a decrease in Rhodamine 123 uptake, which indicates a loss of MMP. Additionally, glucose consumption and lactate production rates were reduced during the 6‐h period following the exposure. These results support the hypothesis that a subpopulation of cells at the end of an acute exposure may be activated for apoptosis, suggesting a role for apoptosis markers during risk assessment for chloroform. Copyright © 2005 John Wiley & Sons, Ltd.