The metabolism of xenobiotic compounds byHymenolepis diminuta(Cestoda: Cyclophyllidea)

Abstract

The hydrolytic, reductive and oxidative enzyme systems involved in the phase I biotrans formation of xenobiotic compounds have been investigated inHymenolepis diminuta. AdultH. diminutaare able to carry out a range of hydrolytic and reductive reactions, but in common with other helminths oxidative detoxification reactions were absent (oxidative demethylation, aniline hydroxylation, nitrobenzene hydroxylation, biphenyl hydroxylation). These oxidative reactions were readily demonstrated in rat liver. Extracts ofH. diminutahydrolysed nitrophenylphosphates and inorganic pyrophosphate, but not arylsulphates, nor could epoxide hydratase activity be detected.N-Deacetylaseactivity was present. However,O-deacetylase activity could not be demonstrated, although butyrate and palmitate, but not benzoate, esters were hydrolysed.H. diminutawas capable of hydrolysing a range of a-and β-glycosides, but not β-glucuronides. Extracts ofH. diminutareduced azo-compounds, aldehydes and disulphides, but ketones and aromatic nitro-compounds were not reduced. The phase I detoxification systems ofH. diminutadiffer considerably from those of its rat host; the results also suggest that, within the cestodes, there may be considerable species variation in detoxification reactions.