Abstract: In the silkworm, Bombyx mori, H₂O₂ significantly increases in diapause eggs when diapause initiation is prevented with instant hydrochloric acid (HCl) soaking. The ratio of the reduced glutathione (GSH)/oxidized glutathione (GSSG) is indicative of the oxidative stress. To investigate whether instant HCl soaking causes the oxidative stress in diapause eggs of the silkworm, GSH and GSSG levels and glutathione-S-transferase (GST) activities in diapause eggs soaked with HCl for 5 min at 24 h after oviposition were determined using spectrophotometric methods with those without soaking with HCl as the control. Total glutathione content (GSH+2GSSG), GSH content, GSSG content, GSH/GSSG ratio and GST activity in diapause eggs soaked with HCl were equal to 204%, 78%, 550%, 14% and 97% of those in unsoaked diapause eggs at 48 h after oviposition, respectively. It is so inferred that the marked decline of GSH/GSSG ratio in diapause eggs soaked with HCl is resulted from the stronger oxidation of GSH to GSSG, which causes the transition from the reducing conditions to the peroxidatic conditions.

Key words: Bombyx mori, diapause eggs, instant HCl soaking, glutathione, glutathione-S-transferase, peroxidation