The pesticide hexachlorobenzene induces alterations in the human erythrocyte membrane

Hexachlorobenzene (HCB) is one of the most widely distributed organochlorin e residues in the biosphere. High concentrations have been found in develop ing and industrialized countries. Due to its persistence in the environment it has been detected in fish, birds, eggs, and human adipose tissue and se rum, and chronic administration of this compound causes a number of toxic e ffects. Due to the Lipophilic character of HCB, lipid-rich membranes are im portant targets for its interaction with Living organisms. HCB was incubate d with human erythrocytes and molecular models of biomembranes in order to better understand the molecular mechanism of its interaction with cell memb ranes. The models consisted of bilayers of dimyristoylphosphatidylcholine ( DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of pho spholipid classes located in the outer and inner monolayers of the human er ythrocyte membrane, respectively. Electron microscopy showed that HCB inter acted with the erythrocyte membrane, modifying its normal discoid morpholog y to cup-shaped stomatocytes. This result indicates that HCB was inserted i n the inner layer of the red cell membrane, a conclusion supported by X-ray diffraction analyses of DMPC and DMPE bilayers. In fact, HCB incorporated into and perturbed the bilayer structures of DMPC and DMPE. However, the ex tent of the interaction was higher in DMPE. Therefore, the experimental res ults confirmed the important role played by the phospholipid bilayer in the molecular mechanism of HCB interaction with the red cell membrane. (C) 199 9 Academic Press.