EFFECT OF THE PYRETHROID INSECTICIDE ALLETHRIN ON MEMBRANE FLUIDITY

Allethrin is a widely used pyrethroid insecticide with an alkenylmethy lcyclopentenolone group in its structure. We have analyzed its interac tion with model and native membranes using DPH and its polar derivativ e TMA-DPH fluorescence polarization. Allethrin modified the bilayer or der in the temperature range of the phase transition when incorporated into liposomes made with dimyristoyl-(DMPC), dipalmitoyl-(DPPC) and d istearoyl-(DSPC) phosphatidylcholine. In DMPC:allethrin mixtures the p yrethroid decreased the bilayer order in the gel phase, without alteri ng the liquid-crystalline one. In native membranes, DPH and TMA-DPH fl uorescence polarization remained unchanged after incubation with allet hrin. The release of hemoglobin was notably facilitated by the incorpo ration of allethrin into human erythrocytes. The results are discussed in terms of a possible aggregation of the insecticide in the lipid bi layer to create special domains with a consequent increase in membrane instability.