Nitric oxide (NO) is a highly reactive, membrane-permeable free radical, which has recently emerged as an important antioxidant. Here we investigated the protective effect of NO against the toxicity and NH4+ accumulation in rice leaves caused by excess CuSO4 (10mmol L(-1)). It was found that free radical scavengers (sodium benzoate, thiourea, and reduced glutathione) reduced the toxicity and NH4+ accumulation in rice leaves caused by excess CuSO4. NO donor sodium nitroprusside (SNP) was also effective in reducing CuSO4-induced toxicity and NH4+ accumulation in rice leaves. The protective effect of SNP on the toxicity and NH4+ accumulation can be reversed by 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethyl- imidazoline-1-oxyl-3-oxide, a NO scavenger, suggesting that the protective effect of SNP is attributable to NO released. Results obtained in the present study suggest that reduction of CuSO4-induced toxicity and NH4+ accumulation by SNP is most likely mediated through its ability to scavenge active oxygen species.

中文翻译：

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一氧化氮降低了水稻叶片中铜的毒性和铜诱导的 NH4+ 积累

一氧化氮 (NO) 是一种高反应性、可渗透膜的自由基，最近已成为一种重要的抗氧化剂。在这里，我们研究了 NO 对过量 CuSO4 (10mmol L(-1)) 引起的水稻叶片毒性和 NH4+ 积累的保护作用。发现自由基清除剂（苯甲酸钠、硫脲和还原型谷胱甘肽）降低了由过量 CuSO4 引起的水稻叶片中的毒性和 NH4+ 积累。NO 供体硝普钠 (SNP) 也能有效降低 CuSO4 诱导的毒性和水稻叶片中 NH4+ 的积累。SNP 对毒性和 NH4+ 积累的保护作用可以通过 NO 清除剂 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide 逆转，表明 SNP 的保护作用归因于释放的 NO。