Mr. Moyaquiles et al., INTERACTIONS OF THE PYRETHROID INSECTICIDE ALLETHRIN WITH LIPOSOMES, Archives of biochemistry and biophysics, 312(1), 1994, pp. 95-100
The action of allethrin, a pyrethroid with an alkenylmethylcyclopenten
olone group, on the thermotropic properties of lipid vesicles has been
investigated. Application of turbidimetry and differential scanning c
alorimetry to liposomes made with dimyristoyl- (DMPC), dipalmitoyl- (D
PPC), and distearoyl- (DSPC) phosphatidylcholine, containing variable
concentrations of allethrin, showed that the pyrethroid lowers the tem
perature at which the phase transition of the phospholipid occurs. Fur
thermore, allethrin produces a broadening of the peak which marks the
gel to liquid-crystalline phase transition. The appearance of a second
peak as the allethrin concentration in the membranes rises indicates
a limited miscibility of the pyrethroid in lipids. Incorporation of al
lethrin in carboxyfluorescein-trapped unilamellar liposomes, followed
by incubation at several temperatures, enhances carboxyfluorescein rel
ease in allethrin-containing vesicles. The results are discussed in te
rms of a preferential localization of allethrin in an extended orienta
tion in the bilayer with the carbonyl group of the alkenylmethylcyclop
entenolone residue in the lipid mater interface and the cyclopropaneca
rboxylate moiety between the hydrocarbon acyl chain of the phospholipi
ds. (C) 1994 Academic Press, Inc.