Studying the toxic effects of long-term exposing fruit flies to phenol is the object of this study. The induction of the glutathione S-transferases enzymatic activities, the change in the amount of mRNA related to phenol exposure, the change in survival rate of adult fruit flies, and the chemical interaction between phenol and benzene were the problems to be investigated. Glutathione S-transferases were separated by affinity chromatography and the mRNAs levels were quantified by reverse-transcription polymerase chain reaction. Long-term feeding phenol to wild type fruit flies had caused some toxic effects included increasing the resistance to phenol toxicity, lowering the benzene toxicity, and induction of glutathione S-transferases enzymatic activities. But no significant change in the amount of glutathione S-transferases GstD1 and GstD5 mRNAs had occurred. From these results, we concluded that fruit flies could develop resistance to phenol by decreasing its toxicity; phenol was a inducer of glutathione S-transferases; phenol could increase the glutathione S-transferases enzymatic activities by increasing the amount of proteins; phenol exposure could decrease the benzene toxicity; no new glutathione S-transferase isozyme subunit was induced; and the level of GstD1 and GstD5 mRNAs did not significantly increase in phenol-treated strain.

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Rat liver and house fly, Musca domestica L., glutathione S-transferases were purified by affinity chromatography and chromatofocusing. The specific activity with alpha-naphthyl acetate (a substrate, for general esterase activity) was determined. Some of the esterase activity that is normally assayed for resistance is apparently caused by the activity of the glutathione S-transferase.

The acidic glutathione S-transferases from a CSMA (susceptible) strain and a Cornell-R (resistant) strain of houseflies were purified and separated utilizing affinity chromatography followed by chromatofocusing. Nine fractions were isolated from each house fly strain. Fraction 1 had the highest 1-chloro-2,4-dinitrobenzene vs. 1,2-dichloro-4-nitrobenzene ratio (CDNB/DCNB ratio) in both strains and the ratio of all the other fractions tended to decrease as the isoelectrical points decreased except for fractions 4 and 9. Most fractions from the CSMA strain had higher CDNB conjugation activities than the fractions from the Cornell-R strain, but all the fractions from the CSMA strain had lower DCNB conjugation activities than fractions from the Cornell-R strain. Steady-state kinetics of all the fractions were examined. The Km values obtained from both strains ranged from 0.36 to 1.12 mM, while the Vmax value ranged from 3.0 to 32.6 mumol/min/mg. In the 100,000 g supernatant, the CDNB specific activities in the CSMA strain was about 1/3 of the activity in the Cornell-R strain but it was about 1.5-fold following affinity chromatography. The specific activity for DCNB measured in the CSMA strain was only 1/5 of the activities of the Cornell-R strain in the 100,000 g supernatant, but was about the same after affinity chromatography. The difference was due to the selectivity of the affinity column used in the current study.