EFFECT OF FENVALERATE, A PYRETHROID INSECTICIDE ON MEMBRANE FLUIDITY

Fenvalerate is a commonly used pyrethroid insecticide, used to control a wide range of pests. We have studied its interaction with the membr ane using fluorescence polarization and differential scanning calorime try (DSC) techniques. Fenvalerate was found to decrease the DPH fluore scence polarization value of synaptosomal and microsomal membrane, imp licating that it makes the membrane more fluid. At different concentra tions of fenvalerate, the activation energy of the probe molecule in t he membrane also changes revealed from the change in slope of the Arrh enius plot. At higher concentrations the insecticide slowly saturates the membrane. The effects of fenvalerate on model membrane were also s tudied with liposomes reconstituted with dipalmitoylphosphatidylcholin e (DPPC). Fenvalerate decreased the phase transition temperature (T(m) ) of DPPC by 1.5 C-degrees at 40 muM concentration, but there was no e ffect on the cooperativity of the transition as interpreted from the D SC thermogram. From the change in the thermogram profile with fenvaler ate it has been interpreted that it localizes in the acyl chain region of the lipid, possibly between C10 and C16 region and weakens the acy l chain packing. Fenvalerate was also found to interact with DPPC lipo somes containing cholesterol to fluidize it.