Kenichi Mikitani

Ecdysteroid receptor binding activity and ecdysteroid agonist activity at the level of gene expression are correlated with the activity of dibenzoyl hydrazines in larvae of Bombyx mori

Abstract Ecdysteroid activities of two dibenzoyl hydrazines (RH 5849 and RH 5992) were examined using the Kc cell line. Gene expression activity was determined in the transient assay utilizing the ecdysteroid responsive Drosophila melanogaster hsp27 promoter gene. Ecdysteroid receptor binding (EC 50 = 3.0 × 10 −7 m ), induction of ecdysteroid responsive gene expression (EC 50 = 3.0 × 10 −6 m ) and induction of cell morphological change (EC 50 = 3.0 × 10 −7 m ) were 13-fold, 7-fold and 13-fold higher in RH 5992 than in RH 5849, respectively. The addition of 10 ppm RH 5849 to the diet induced head capsule slippage in Bombyx mori larvae and most of the larvae died. RH 5992 caused the same response at 1 ppm. The higher insecticidal activity of RH 5992 compared to RH 5849 is likely caused by its higher ecdysteroid agonist activity at the molecular level.