Toxicity of local anaesthetics on myogenic cells in culture

Toxicity of local anaesthetics on chick myogenic cells (mononucleated myoblasts and multinucleated myotubes) in culture was examined. Following treatment with the drugs, myogenic cells showed some morphological changes and finally detached from the culture dishes. In most cases, the toxic effect was estimated by the amount of cells detached quantitatively. The indices used to show the amount of cells were the deoxyribonucleic acid (DNA) and creatine kinase activity content of mono- and multinucleated cells remaining on the dishes, respectively. Dibucaine was more toxic than bupivacaine, mepivacaine, tetracaine and procaine, and was examined in detail. The toxicity was dependent on its concentration, pH and temperature of the reaction medium in both mono- and multinucleated cells, and paralleled the concentration of uncharged form of the drug, suggesting that this form in external medium was actually toxic.