DISTRIBUTION OF GLUTATHIONE-S-TRANSFERASE ACTIVITY IN INSECT TISSUES

Distribution of glutathione S-transferases (GST) activity in insect tissues was studied using 1-chloro-2,4-dinitrobenzene (CDNB), 2,4-dinitrophenyl benzeresulforate (DNPES), 1,2-dichloro-4-nitrobenzene (DTNB) and fenitrothion (O,O-dimethyl O-3-methyl-4-nitrophenyl phosphorothioate) as substrates. The highest GST activity was found in the Malpighian tubes. CDNB and DNPBS conjugation activities in the American cockroach, Periplaneta americana (Orthoptera: Blattidae), were distributed mainly in Malpighian tubes, fat body, guts, nerve cord and testis, while blood and muscle had low activity. Similar results were obtained in the common cutworm, Spodoptera litura (Lepidoptera, Noctuidae) and the rice stem borer, Chilo suppressalis (Lepidoptera: Pyralidae). As for DCNB conjugation activity, each insect showed different distribution patterns among tissues from that of CDNB and DNPBS. Fenitrothion conjugation activity of the American cockroach and the common cutworm was also the highest in Malpighian tubes. Fenitrothion was degradaded mainly by O-alkyl conjugation.