Inhibition of UDP-N-acetylglucosamine Transport by Diflubenzuron across Biomembranes of the Midgut Epithelial Cells in the Cabbage Armyworm, Mamestra brassicae L.

Abstract

The midguts from the last instar larvae of the cabbage armyworm, Mamestra brassicae L., were incubated in the Grace's medium containing ¹⁴C-N-acetylglucosamine with or without diflubenzuron. Accumulation of ¹⁴C-UDP-N-acetylglucosamine was observed in the diflubenzuron-treated midguts. The phospholipid composition was examined in the midguts after they had been incubated in the presence of ¹⁴C-acetic acid as a precursor. No difference was observed between the diflubenzuron-treated and the untreated midguts. When the midguts were turned inside out, ligated at the both ends, incubated in the presence of ¹⁴C-N-acetylglucosamine, and then, UDP-N-acetylglucosamine in the medium as well as in the tissues and chitin were separately analyzed, the total radio-activity transported through the microvilli membranes in the diflubenzuron-treated midguts was less than that in the control midguts. ¹⁴C-UDP-N-acetylglucosamine was also found to accumulate in the treated tissues. From these results, the mode of action of diflubenzuron seems to be the inhibition of UDP-N-acetylglucosamine transport through the biomembrane.