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.