Influence of enzyme levels on the toxicity and in vitro metabolism of 2,2',5-trichlorobiphenyl in houseflies.

F Hu, W Yuan, X Wang, Z Sheng, Y Yuan, C Qin, C He, T Xu

Index: Ecotoxicol. Environ. Saf. 28(2) , 111-20, (1994)

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Abstract

Adult female houseflies (Musca domestica) were topically dosed with 10, 15, and 20 micrograms of 2,2',5-trichlorobiphenyl (PCB-18) in acetone at 1, 5, and 15 days following emergence. These doses caused a significant decrease in the mean survival time in 5-day-old flies. LT50's (time for 50% death) were dramatically reduced in 5-day-old flies, whereas no significant difference was found at any treatment level in 15-day-old flies. Abdomenal microsomal enzyme levels were determined by the rate of O-dealkylation of (p-nitrophenyl)ethyl ether for 1-, 5-, 11-, and 15-day-old female houseflies. The highest levels were found in 5-day-old flies and the lowest in 15-day-old flies. The greatest metabolism of PCB-18 by housefly microsomes also occurred in 5-day-old flies. The enzyme levels, metabolism, and toxicity suggest that PCB-18 is bioactivated to a product(s) which reduces the mean survival time of houseflies.