NMR analysis of the effect of validoxylamine A, a trehalase inhibitor, on the larvae of the cabbage armyworm

Injection of trehalase inhibitor, validoxylamine A (VAA, 10 μg/insect) evoked relaxation of segmental muscle and decrease of the pulsation of dorsal vessel in the final instar larvae of Mamestra brassicae. Ninety percent of the trehalase activity of the midgut was inhibited in a day. The larvae died afterward of incomplete pupation. We analysed the haemolymph components after the injection by 1 H NMR and 13 C NMR to elucidate the cause of the abnormality. Trehalose was actively synthesized from glucose regardless of VAA treatment and utilization of trehalose was suppressed by VAA. Trehalose concentration rose to 1.7 and 2.0 times of the control 1 and 3 days after injection respectively, and to 3.3 times at prepupal stage. Amino acid concentrations decreased once at the middle of the instar, but became at higher level than the control at prepupal stage. At this stage, phosphorylcholine level fell with increase of choline, and N-acetylglucosamine appeared. Accumulation of the components seemed to be caused by inhibition of the utilization of materials for pupal formation.