Exposure of rice seedlings to heat shock protects against subsequent Cd-induced decrease in glutamine synthetase...

In the present study, we investigated the effect of heat shock (HS) on the subsequent Cd-induced decrease in the activity of glutamine synthetase (GS) and increase in the specific activity of protease in rice leaves. HS exposure of rice seedlings for 3h in the dark was effective in reducing subsequent Cd-induced decrease in the activity of glutamine synthetase and increase in the specific activity of protease. The effect of HS can be mimicked by pretreatment of rice seedlings with exogenous H(2)O(2) or reduced glutathione (GSH) under non-HS conditions. We also found that HS protected against subsequent Cd-induced decrease in the activity of GS and increase in the specific activity of protease can be counteracted by imidazole, a NADPH oxidase inhibitor. Pretreatment with buthione sulfoximine (a GSH synthesis inhibitor) under HS conditions enhanced subsequent Cd effects on the activity of GS and the specific activity of protease. Moreover, the effect of BSO can be reversed by the addition of GSH. The mechanisms of the protective effect of HS effect against subsequent Cd effects are discussed.