Comparative detoxication. 9. The metabolism of some halogenated compounds by conjugation with glutathione in the locust

It has been shown that the metabolism of chlorobenzene in locusts and vertebrates is similar, and that the isomeric chlorophenylcysteines and chlorophenylmercapturic acids were present in locust excreta as acid-labile precursors (Gessner & Smith, 1960).Benzyl chloride and p-nitrobenzyl chloride are also metabolized to mercapturic acids in mammals but without the formation of inter- mediate acid-labile precursors.It is known, how- ever, that in mammals S-substituted glutathione derivatives are intermediates in the formation of mercapturic acids from either aromatic compounds or arylalkyl halides (Knight & Young, 1958; Barnes, James & Wood, 1959; Bray, Franklin & James, 1959; Booth, Boyland & Sims, 1960).We wished to see if cysteine or glutathione con- jugates were formed in locusts from compounds, e.g.benzyl chloride, that contain labile or reactive halogen, since these simple compounds might serve as models for the more complex chlorinated in- secticides.Little attention has been paid to de- toxications of this type in insects, and the observa- tion of Bettini & Boccacci (1958) that bromoacetic acid was metabolized by cockroaches to S-(carboxymethyl)glutathione appears to be an isolated case.Glutathione conjugates or cysteine con- jugates have also been suspected as metabolites of Gammexane (y-hexachlorocyclohexane) in flies (Bradbury & Standen, 1959), but the evidence is indirect and it is not known whether the sulphurcontaining metabolites are aromatic or cycloaliphatic. EXPERIMENTALMaterials Locu8ta and tismue preparations.Fifth-instar hoppers or adults of Schistocerca gregaria were obtained from the Anti-Locust Research Centre and kept on a grass diet as recommended by Hunter-Jones (1956).Compounds were administered by injection into the thorax in acetone solution (10pd.containing 100lg.).Locust 'fillets' were prepared by cutting off the terminal segment of the hoppers, drawing out the head and gut and dividing the carcass by ventral and dorsal cuts.The two half-carcasses (i.e. the 'fillets') consisted mainly of fat * Part 8: Gessner & Smith (1960).29