The aim of present project was to find out if in vivo contact of Haemonchus contortus with benzimidazole anthelmintic flubendazole (FLU) during treatment of its hosts (sheep) with low doses of FLU affects helminths’ drugmetabolizing enzyme activities. Four groups of lambs, experimentally infected with H. contortus , were treated three-times orally with 0.0, 0.25, 0.50 or 1.00 mg per kg of body weight of FLU in three consecutive days. Twenty four hours after the last FLU dose, the nematodes were isolated, homogenized and subcellular fractions were prepared. In these subcellular fractions, biotransformation of FLU and the activities of carbonyl reducing enzymes and conjugation enzymes were assayed. The results showed that H . contortus enzymes were able to conjugate p-nitrophenol with glucose but not with glucuronic acid. The exposure of H.contortus to FLU (the highest FLU dose) caused a significant increase in activities of FLU reductases, D,L-glyceraldehyde reductases and glutathion S-transferases.

Keywords: Benzimidazoles, drug metabolism, enzyme modulation.
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