
TY  - JOUR
A1  - Schuntner, CA 
A1  - Thompson, PG 
T1  - Mechanisms of Resistance to Bromophos-ethyl in Two Strains of the Cattle Tick Boophilus microplus
JF  - Australian Journal of Biological Sciences
JO  - Aust. Jnl. Of Bio. Sci.
Y1  - 1978
VL  - 31
IS  - 4
SP  - 317
EP  - 326
KW  - 
UR  - https://doi.org/10.1071/BI9780317 
N2  - B. micro plus larvae of the organophosphorus-resistant Biarra and Mt Alford strains were respectively 8 x and 35 x resistant to bromophos-ethyl compared with larvae of the standard organophosphorussusceptible Yeerongpilly strain. Both resistant strains had acetylcholinesterase with decreased sensitivity to inhibition by the oxon of bromophos-ethyl in vitro; this was the only resistance mechanism apparent in the Biarra strain but Mt Alford larvae were protected additionally by increased metabolism of the oxon in vivo to water-soluble products. Total degradation rates for the parent chemical were similar in all strains and relatively slow. Both bromophos-ethyl and its oxon were potent inhibitors of mixed-function oxidase in vivo and it seemed that the slow oxidative metabolism of bromophos-ethyl (the major pathway) could be attributed to substrate and/or product inhibition. No phenolic metabolites were detected and the major water-soluble metabolite was identified electrophoretically as 2,5-dichlorophenyl-o-ethyl phosphate. Some debrominated oxon was detected in all samples of larvae after dosage with bromophos-ethyl or with its oxon, indicating that oxidation of bromophos-ethyl to the oxon, debromination of the oxon followed by deethylation was a major degradative sequence. 
ER  -

