Different effects of Type I and Type II pyrethroids on erythrocyte plasma membrane properties and enzymatic activity in rats.

Pyrethroids are divided into two groups according to their chemical structures: type I pyrethroids are devoid of a cyano moiety at the alpha-position (i.e. permethrin, PERM), while type II pyrethroids have an alpha-cyano moiety (i.e. cypermethrin, CY). Type I pyrethroids cause a type I poisoning syndrome or "T syndrome", whereas type II pyrethroids induce a type II choreoathetosis syndrome, known as "CS syndrome". The aim of the present work is to compare the effect of PERM and CY on erythrocyte plasma membrane fluidity of rats, treated orally for 60 days with low and high doses of these insecticides. The different modifications induced by pyrethroids on lipid peroxidation, osmotic fragility and the antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)) were measured. The data obtained show that PERM, which proved more permeable than CY, produced an increase of fluidity and polarity in the hydrophilic-hydrophobic region of the erythrocyte bilayer even at low doses. Also at high doses, filtering through the membrane more easily, the PERM influenced more markedly the intracellular enzymatic activity, compared with CY, reducing GPx activity and increasing SOD activity. Because of its hydrophilic character, CY limits oxidative damage in the erythrocyte cytosol at high doses.