Toxic effects of the fungicide benomyl on cell membranes

This paper examines the toxicity of the fungicide benomyl towards cell membranes. Approaches to this aim were the study of its acute effects on the stimulatory response of a frog neuroepithelial synapse and on membrane models. The latter consisted of large unilamellar vesicles of dimyristoylphosphatidylcholine (DMPC) and phospholipid multilayers built-up of DMPC and dimyristoylphosphatidylethanolamine (DMPE). Results showed that benomyl at concentrations as low as 10 μM decreased the stimulatory response of the potential difference (PD) and the short-circuit current (SCC) of the frog sympathetic junction. It is concluded that benomyl caused a dose-dependent reduction in the response of a sympathetic junction of the frog to stimulation leading to Cl⁻ channel perturbation. This finding might be explained from those obtained from fluorescence spectroscopy and X-ray diffraction studies on membrane models. In fact, similar (0.01–1.0 mM) concentrations induced structural perturbations in DMPC large unilamellar vesicles and multilayers, respectively. Although it is still premature to define the precise molecular mechanism of benomyl toxicity, the experimental results confirm the important role played by the phospholipid bilayers in the interaction of the pesticide with cell membranes.