In vitro toxicity of solubilized 2,3,4-trimethylpentane I. Cytotoxicity and metabolism of TMP using primary hepatocytes

Summary Primary rat hepatocyte suspension cultures (∼2×10⁶ cells) exposed to solubilized 2,3,4-trimethylpentane at concentrations ranging from 7.9 to 31.5 mM under two different culture conditions resulted in a linear dose response, as determined by lactate dehydrogenase leakage and viability data. A significant increase in the 2,3,4-trimethylpentane effective concentration 50 for primary hepatocytes occurred when exposures were implemented in medium containing 0.05% albumin. The effective concentration 50 for hepatocytes exposed to 2,3,4-trimethylpentane in medium lacking and containing albumin were 17.1 and 20.7 mM, respectively. Metabolite analysis by gas chromatography-mass spectrometry of supernatant (lacking or containing albumin) and cell extracts from hepatocyte cultures exposed to 2,3,4-trimethylpentane for 4 h indicated the presence of three metabolites: 2,3,4-trimethyl-1-pentanol, 2,3,4-trimethyl-2-pentanol, and 2,3,4-trimethyl-1-pentanoic acid. Electron microscopic examination of 2,3,4-trimethylpentane-exposed primary hepatocytes indicated ultrastructural changes which included abnormal condensed chromatin association with the nuclear membrane, swollen mitochondria, increased amounts of cytoplasmic lipid, significant los of microvilli from the cell surface, increased vacuolation, and increased numbers of peroxisomes. Although these changes were observed under both culture conditions, they were more severe in cultures lacking albumin. This study indicates that primary hepatocyte suspension cultures provide a useful system for rapidly identifying liver metabolites of selected test compounds of interest. Animals used in this study were handled in accordance with the principles stated in the Guide for the Care and Use of Laboratory Animals, prepared by the Committee on Care and Usage of Laboratory Animals of the Institute of Laboratory Animals Resources, National Research Council, DHHS, National Institute of Health publication 85–23, 1985, and the Animal Welfare Act of 1966, as amended. This material has been funded wholly or in part by the United States Air Force under contract F33615-85-C-0532 to NSI Technology Services Corporation. It has been subject to review by the United States Air Force and it has been approved for publication as a customer document. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.