Changes induced by malathion, methylparathion and parathion on membrane lipid physicochemical properties correlate with their toxicity

Abstract

Perturbations induced by malathion, methylparathion and parathion on the physicochemical properties of dipalmitoylphosphatidylcholine (DPPC) were studied by fluorescence anisotropy of DPH and DPH-PA and by differential scanning calorimetry (DSC). Methylparathion and parathion (50 microM) increased the fluorescence anisotropy evaluated by DPH-PA and DPH, either in gel or in the fluid phase of DPPC bilayers, but mainly in the fluid phase. Parathion is more effective than methylparathion. On the other hand, malathion had almost no effect. All the three xenobiotics displaced the phase transition midpoint to lower temperature values and broadened the phase transition profile of DPPC, the effectiveness following the sequence: parathion>methylparathion>>malathion. A shifting and broadening of the phase transition was also observed by DSC. Furthermore, at methylparathion/lipid molar ratio of 1/2 and at parathion/lipid molar ratio of 1/7, the DSC thermograms displayed a shoulder in the main peak, in the low temperature side, suggesting coexistence of phases. For higher ratios, the phase transition profile becomes sharp as the control transition, but the midpoint is shifted to the previous shoulder position. Conversely to methylparathion and parathion, malathion did not promote phase separation. The overall data from fluorescence anisotropy and calorimetry indicate that the degree of effect of the insecticides on the physicochemical membrane properties correlates with toxicity to mammals. Therefore, the in vivo effects of organophosphorus compounds may be in part related with their ability to perturb the phospholipid bilayer structure, whose integrity is essential for normal cell function.

The effect of exposure to chlorfenvinphos on lipid metabolism and apoptotic and necrotic cells death in the brain of rats

“…Indices of lipid metabolism in the brain Brain cells quantification the fluidity of cellular and sub-cellular membranes in the CNS system leading to their improper function (Blasiak, 1993;Videira et al, 2001). The increased concentrations of TCh and TG with the elevated TCh/PL ratio, and decreased PL concentration observed in the brain of the rats exposed to chlorfenvinphos allow for the conclusion that this pesticide might decrease fluidity and disturb function of cellular membranes of the nervous cells.…”

Malathion-induced Oxidative Stress in Rat Brain Regions

“…However, some studies indicate that other biochemical targets may be affected by OP insecticides [5,6]. Moreover, the lipophilic nature of OPs facilitates their interaction with the cell membrane and leads to perturbations of the phospholipid bilayer structure [7]. The toxicity of OP agents may be due, at least in part, to the formation of reactive oxygen species (ROS), leading to lipid peroxidation, which is generally assessed by an increase in the levels of thiobarbituric acid reactive substances (TBARS) [8][9][10].…”

Activities of brain antioxidant enzymes, lipid and protein peroxidation

“…The increased level of MDA and carbonyl groups in the rats ' brains after chlorpyrifos treatment suggests enhanced production of reactive oxygen species, including hydroxyl radicals, which act on a component of membranes, unsaturated fatty acids of phospholipids [22,28]. Moreover, OPs have a lipophilic nature, which facilitates their interaction with the cell membrane and leads to perturbations of the phospholipids bilayer structure [33].…”