Interactive effects between EBI fungicides (prochloraz, propiconazole and penconazole) and OP insecticides (dimethoate, chlorpyrifos, diazinon and malathion) in the hybrid red-legged partridge

Abstract

Abstract The toxicokinetic interactions between the ergosterol-biosynthesis-inhibiting (EBI) fungicides prochloraz, propicon-azole, and penconazole and the organophosphorus (OP) insecticides dimethoate, chlorpyrifos, and diazinon have been studied in the hybrid red-legged partridge. The inhibition of serum butyrylcholinesterase (BuChE) activity provided a useful biochemical indicator of the generation of the toxic oxon metabolites of these OP insecticides. Birds pretreated with 180 mg/kg prochloraz tended to show a greater inhibition of serum BuChE activity at 1, 4, and 24 h following oral exposure to either of the OPs dimethoate (3 mg/kg) or chlorpyrifos (9 mg/kg) compared to birds pretreated with corn oil. Prochloraz-pretreated birds also showed a tendency toward an increased inhibition at 24 h following dosing with the OP diazinon (4.3 mg/kg) compared to corn oil controls. In the case of dimethoate, the inhibition of serum BuChE activity was significantly greater in treated birds than controls at 24 h. Birds pretreated with the EBI fungicide propiconazole (200 mg/kg) showed a similar inhibition of serum BuChE activity to those pretreated with corn oil following administration of 167 mg/kg malathion. Pretreatment with the EBI fungicide penconazole (200 mg/kg) produced significantly greater depression of serum BuChE activity at 1, 4, and 24 h after dosing with malathion, when compared to corn oil controls. The tendency toward increased inhibition of serum BuChE activity by each of the OPs in prochloraz-pretreated birds was attributed to an increased activation of the compound to its active oxon form as a consequence of induction of microsomal monooxygenases by prochloraz.