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Pyrethroids are potent synthetic insecticides which have been increasingly employed in recent years. Such compounds have been shown to bind covalently to hepatic proteins. Covalent binding is often associated with toxic effects. Possible cytotoxic, cytogenotoxic and allergenic effects could be due to covalent binding of these compounds and/or their metabolites to endogenous macromolecules. In the present paper we examine possible cytotoxic effects of certain pyrethroids on human lymphocytes and L 1210 lymphoblastoid mouse cells, cytogenotoxic effects with micronuclei test and allergenic effects with Magnusson and mast cell degranulation tests. Under our experimental conditions, the tested compounds showed neither acute cytotoxic nor cytogenotoxic effects, though, Cismethrin presented slight antimitotic effects statistically different to those with the control. Slight allergenic character of Cismethrin, Bioresmethrin and Deltamethrin was revealed by Magnusson and mast cell degranulation tests.

No abstract

Phenobarbital-induced rat liver homogenate and microsomes were used to study covalent binding of 14C-labelled (at the alcohol moiety) cismethrin, 14C-labelled (at the alcohol and acid moieties) cypermethrin, and 14C-labelled (at the alcohol and acid moieties) deltamethrin. Covalent binding was dependent on pyrethroid concentration. With liver homogenate, inhibition of esterases by tetraethylpyrophosphate and of mitochondrial respiration by rotenone or potassium cyanide only slightly altered the covalent binding level. With microsomes, inhibition of cytochrome P-450 and mixed function oxidases by carbon monoxide and piperonyl butoxide reduced the covalent binding so far as to be nearly absent. Eighty percent inhibition of epoxide hydrolase decreased the covalent binding by 50%. The comparison of data between alcohol and acid labelling of the same pyrethroid suggested that, in vitro, the whole molecule is bound to proteins and that hydrolysis can occur afterwards. The experiments stress the role of cytochrome P-450-dependent monoxygenases in the covalent binding process.