Resistance in the highly DDT-resistant 91-R strain of Drosophila melanogaster involves decreased penetration,increased metabolism,and direct excretion |
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Authors: | Joseph P Strycharz Alice Lao Hongmei Li Xinghui Qiu Si Hyeock Lee Weilin Sun Kyong Sup Yoon Jeffery J Doherty Barry R Pittendrigh J Marshall Clark |
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Institution: | 1. Department of Veterinary & Animal Sciences, University of Massachusetts, Amherst, MA 01003, USA;2. Department of Agricultural Biotechnology, Seoul National University, Seoul 151-742, Republic of Korea;3. Department of Entomology, University of Illinois, Urbana-Champaign, IL 61801, USA |
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Abstract: | Resistance to 4,4′-dichlorodiphenyltrichloroethane (DDT) in the 91-R strain of Drosophila melanogaster is extremely high compared to the susceptible Canton-S strain (>1500 times). In addition to enhanced oxidative detoxification, the 91-R strain also has a reduced rate of DDT penetration, increased levels of reductive and conjugative metabolism, and substantially more excretion than the Canton-S strain. Contact penetration of DDT was ∼30% less with 91-R flies, which also had significantly more cuticular hydrocarbons and a thicker, more laminated cuticle compared to Canton-S flies, possibly resulting in penetration differences. DDT was metabolized ∼1.6-fold more extensively by 91-R than Canton-S flies, resulting in dichlorodiphenyldichloroethane (DDD), two unidentified metabolites and polar conjugates being formed in significantly greater amounts. 91-R flies also excreted ∼4-fold more DDT and metabolites than Canton-S flies. Verapamil pretreatment reduced the LD50 value for 91-R flies topically dosed with DDT by a factor of 10-fold, indicating that the increased excretion may involve, in part, ATP-binding cassette (ABC) transporters. In summary, DDT resistance in 91-R is polyfactorial and includes reduced penetration, increased detoxification and direct excretion. |
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Keywords: | ABC transporters ATP-binding cassette transporter CPM counts per minute DBP dichlorobenzophenone DDA dichlorodiphenyl acetic acid DDD dichlorodiphenyldichloroethane DDE dichlorodiphenyldichloroethylene DDMU dichlorodiphenylmonochloroethylene DDT dichlorodiphenyltrichoroethane DDTase DDT-dehydrochlorinase GC/MS gas chromatograph/mass spectrometry GLC gas&ndash liquid chromatography GSH reduced glutathione GST glutathione S-transferase LSS liquid scintillation spectrophotometry R%S relative percent synergism of the susceptible Canton-S strain R%S(R) relative percent synergism of the DDT-resistant 91-R strain SR synergistic ratio TLC thin-layer chromatography |
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