Abstract: For diapausing eggs of the silkworm, Bombyx mori, diapause initiation is prevented with instant hydrochloric acid (HCl) soaking, which can cause the marked enhancement of oxygen consumption and the inhibition of sorbitol accumulation. NAD(H) and NADP(H) levels in diapause eggs and those soaked with HCl for 5 min at 24 h after oviposition were determined using HPLC methods. From 24 h to 72 h after oviposition, levels of NAD, NADH, NADP and NADPH in diapausing eggs decreased by 30%, 37%, 50% and 4%, respectively, whereas those in diapausing eggs soaked with HCl increased by 77%, 46%, 142% and 241%, respectively. Moreover, no significant effect of HCl on both NADH/NAD and NADPH/NADP ratios was observed. It is so inferred that, in diapausing eggs soaked with HCl, the marked increase of NAD(H) is involved in the marked enhancement of oxygen consumption, whereas the enhancement of NADP(H) is related to the stronger biosynthesis rather than the inhibition of sorbitol accumulation.

Key words: Bombyx mori, diapause, diapause eggs, instant HCl soaking, NAD(H), NADP(H)