Article

Applied Biochemistry and Biotechnology

, Volume 150, Issue 3, pp 243-257

Non-Selective Toxicological Effects of the Insect Juvenile Hormone Analogue Methoprene. A Membrane Biophysical Approach

  • João P. MonteiroAffiliated withCentro de Neurociências e Biologia Celular; Department of Biochemistry, University of Coimbra
  • , Romeu A. VideiraAffiliated withHigher School of Technology, Polytechnic Institute of Viseu
  • , Manuel J. MatosAffiliated withCentro de Neurociências e Biologia Celular; Department of Biochemistry, University of Coimbra
  • , Augusto M. DinisAffiliated withLaboratório de Microscopia Electrónica, Department of Botany, University of Coimbra
  • , Amália S. JuradoAffiliated withCentro de Neurociências e Biologia Celular; Department of Biochemistry, University of CoimbraDepartment of Biochemistry, University of Coimbra Email author 

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Abstract

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.

Keywords

Methoprene Lipid dynamics Differential scanning calorimetry Fluorescence polarization Cell ultrastructure Bacillus stearothermophilus