Tissue Distribution and Properties of Glutathione S-transferases in Micromelalopha troglodyta (Lepidoptera: Notodontidae)

Abstract

The small prominent, Micromelalopha troglodyta (Graeser) (Lepidoptera: Notodontidae), is an important pest of poplar in China. Glutathione S-transferases are known to be responsible for adaptation mechanisms of M. troglodyta. Thus, the tissue distribution and kinetic constants of glutathione S-transferase activity in the small prominent were studied. Significant differences in glutathione S-transferase (GST) activity and distribution percentages of GST activity and kinetic characteristics were observed among 4 tissues (head, midgut, fat body and integument). Furthermore, the inhibition of glutathione S-transferase activity in 4 tissues by 21 inhibitors was conducted. The results showed the inhibition of GST activity of different tissues by 21 inhibitors is different. For GST activity in heads, chlorpyrifos, profenofos, lambda-cyhalothrin, fipronil and quercetin were the best inhibitors tested. Tannic acid was the most potent inhibitor of midgut GST activity. In the fat body, GST activity was inhibited most by tannic acid, chlorpyrifos and profenofos. The inhibitory effect of profenofos and phoxim was highest for GST activity in the integument. Our results showed that glutathione S-transferases in different tissues are qualitatively different in isozyme composition and thus different in sensitivity to inhibitors.