Local anaesthetic induced turbidity increases: implications of interactions with intact bacterial cells and with subcellular fractions.

Four local anaesthetics (LAs), amethocaine and procaine (esters) and cinchocaine and lignocaine (amides) have been assessed in terms of their ability to induce turbidity increases in non-growing cells of Escherichia coli suspended in a carbohydrate free defined medium (CFM) or distilled water or in 0.2 M phosphate buffer. Procaine and lignocaine did not induce turbidity increases. The turbidity increase-LA concentration profiles for both amethocaine and cinchocaine are similar in all three systems. Slight variation are discussed in terms of the ionic content of the suspending media. Interactions between LAs and dispersed systems comprising: cell envelope preparations, cytoplasmic contents, lipid depleted cells and cell lipid dispersion, are also described. Transmission electron micrographs of LA treated cells are presented and the use of uranyl acetate as a 'vital' stain is illustrated. Results are discussed in terms of LA lipophilicity and the effectiveness of LAs in precipitating intracellular materials at high concentrations.