In vitro toxicity screening using cultured rat skeletal muscle cells. I. Surfactants and mitochondrial poisons

The suitability of a test system using primary cultures of spontaneously contracting rat skeletal muscle cells for assessing effects of chemicals relevant to their toxicity in vivo was evaluated. The effects of ethanol and dimethyl sulphoxide, selected surfactants (digitonin, sodium dodecyl sulphate and Triton X-100) and selected mitochondrial poisons (antimycin A, 2,4-dinitrophenol and pentachlorophenol) on these cultures were assessed. Three endpoints, (1) spontaneous contractility, (2) gross structural membrane integrity and (3) energy metabolism, were studied by determining the reduction in the number of contracting muscle cells, leakage of cytosolic creatine kinase and changes in glucose consumption, respectively. Cells were also screened microscopically for morphological signs of intoxication. Exposure times of 1 and 24 hr were used. Contractility and glucose consumption frequently proved to be more sensitive parameters than loss of intracellular creatine kinase indicating cell death. Most often prominent morphological alterations became obvious at concentrations causing minimal cytolethality. The combination of different endpoints and exposure times revealed distinct patterns of concentration-effect relationships, giving some indication of the different modes of action of the model substances. Non-cytotoxic functional alterations of the muscle cell membrane could be distinguished from cytotoxic action. The results indicate that the test system is suitable for assessing specific qualitative and quantitative aspects of toxicity at the cellular level.