Toxic effects of the fungicide benomyl on cell membranes

This paper examines the toxicity of the fungicide benomyl towards cell memb ranes. Approaches to this aim were the study of its acute effects on the st imulatory response of a frog neuroepithelial synapse and on membrane models . The latter consisted of large unilamellar Vesicles of dimyristoylphosphat idylcholine (DMPC) and phospholipid multilayers built-up of DMPC and dimyri stoylphosphatidylethanolamine (DMPE). Results showed that benomyl at concen trations as low as 10 mu M decreased the stimulatory response of the potent ial difference (PD) and the short-circuit current (SCC) of the frog sympath etic junction. It is concluded that benomyl caused a dose-dependent reducti on in the response of a sympathetic junction of the frog to stimulation lea ding to Cl- channel perturbation. This finding might be explained from thos e obtained from fluorescence spectroscopy and X-ray diffraction studies on membrane models. In fact, similar (0.01-1.0 mM) concentrations induced stru ctural perturbations in DMPC large unilamellar Vesicles and multilayers, re spectively. Although it is still premature to define the precise molecular mechanism of benomyl toxicity, the experimental results confirm the Importa nt role played by the phospholipid bilayers in the interaction of the pesti cide with cell membranes. (C) 2000 Elsevier Science Inc. All rights reserve d.