Non-Selective Toxicological Effects of the Insect Juvenile Hormone Analogue Methoprene. A Membrane Biophysical Approach
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- Monteiro, J.P., Videira, R.A., Matos, M.J. et al. Appl Biochem Biotechnol (2008) 150: 243. doi:10.1007/s12010-007-8127-6
The Gram-positive bacterium, Bacillus stearothermophilus, was used as a model organism to identify the non-selective toxic effects of the currently used insecticide methoprene (isopropyl(2E,4E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate). A significant decrease of the yield of bacterial cultures and a premature appearance of ultrastructural abnormalities in cells cultured in the presence of the insecticide were taken as indicators of cytotoxicity. A putative correlation of this cytotoxicity with methoprene-induced perturbations on membrane lipid organization was investigated, using differential scanning calorimetry and the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and its propionic acid derivative (DPH–PA). The membrane physical effects depended on the lipid bilayer composition and packing. The most striking effect was a progressive broadening and shifting to lower temperatures, with increasing methoprene concentrations, of the main transition phase of the dimyristoyl- or dipalmitoylphosphatidylcholine bilayers and of the lateral phase separation of liposomes reconstituted with the lipid extracts of B. stearothermophilus.
KeywordsMethoprene Lipid dynamics Differential scanning calorimetry Fluorescence polarization Cell ultrastructure Bacillus stearothermophilus
differential scanning calorimetry
transmission electron microscopy