INTERACTIVE EFFECTS BETWEEN EBI FUNGICIDES (PROCHLORAZ, PROPICONAZOLEAND PENCONAZOLE) AND OP INSECTICIDES (DIMETHOATE, CHLORPYRIFOS, DIAZINON AND MALATHION) IN THE HYBRID RED-LEGGED PARTRIDGE

The toxicokinetic interactions between the ergosterol-biosynthesis-inh ibiting (EBI) fungicides prochloraz, propiconazole, and penconazole an d the organophosphorus (OP) insecticides dimethoate, chlorpyrifos, and diazinon have been studied in the hybrid red-legged partridge. The in hibition of serum butyrylcholinesterase (BuChE) activity provided a us eful biochemical indicator of the generation of the toxic oxon metabol ites of these OP insecticides. Birds pretreated with 180 mg/kg prochlo raz 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 co rn oil. Prochloraz-pretreated birds also showed a tendency toward an i ncreased 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 treate d 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 a ctivity at 1, 4, and 24 h after dosing with malathion, when compared t o 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 ox on form as a consequence of induction of microsomal monooxygenases by prochloraz.