Jensen D E, Belka G K
Kimmel Cancer Institute, and Department of Biochemistry and Molecular Pharmacology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, U.S.A.
Biochem Pharmacol. 1997 May 9;53(9):1279-95. doi: 10.1016/s0006-2952(96)00860-x.
The tumorigenicity of certain N-nitrosoguanidinium compounds is limited, in rodents, by the propensity of these agents to be detoxified by denitrosation. Previous studies have revealed that rodent glutathione transferase isoenzymes are capable of catalyzing this process, generating exclusively the denitrosated guanidinium compound and S-nitrosoglutathione (GSNO). Experiments considering the denitrosation of 1,3-dimethyl-2-cyano-1-nitrosoguanidine (CyanoDMNG) in rat liver cytosol incubates are reported, with emphasis on the fate of GSNO. Incubates composed with equimolar CyanoDMNG and reduced glutathione (GSH) effected 100% denitrosation; the GSNO yield was less than expected as was the quantity of GSH consumed. When the anticipated 100% yield concentration of GSNO was applied to cytosol incubates, 20-40% of it rapidly disappeared. Nitrosated protein thiols accounted for 35% of the NO moiety released, nitrite ion 30%, and nitric oxide production was detectable. Concomitant with GSNO loss, GSH and oxidized glutathione (GSSG) were generated in yields similar to those detected in the CyanoDMNG/GSH incubates. Thus, the fate of GSNO in cytosol determines the yields of glutathione-based products, and the stoichiometry of the glutathione transferase reaction is demonstrated. In incubates composed with equimolar CyanoDMNG, GSH, and NADPH, denitrosation was again 100%, but GSNO yields were very low and residual GSH increased. Inclusion of NADPH in incubates containing the anticipated 100% yield concentration of GSNO resulted in rapid GSNO degradation, producing GSH and a detected but unidentified product; S-nitrosated protein, nitrite, and nitrate yields were minimal, nitric oxide production was abolished, and incubate response to a mercuric chloride/azo dye assay approached zero. The fate of the NO moiety consequent to this GSNO catabolism is presently unknown.
某些N-亚硝基胍化合物在啮齿动物中的致瘤性受到限制，因为这些物质易于通过脱亚硝化作用进行解毒。先前的研究表明，啮齿动物谷胱甘肽转移酶同工酶能够催化这一过程，仅生成脱亚硝化的胍化合物和S-亚硝基谷胱甘肽（GSNO）。本文报道了在大鼠肝细胞溶胶孵育体系中对1,3-二甲基-2-氰基-1-亚硝基胍（氰基二甲硝基亚硝基胍，CyanoDMNG）脱亚硝化作用的研究，重点关注GSNO的去向。由等摩尔的CyanoDMNG和还原型谷胱甘肽（GSH）组成的孵育体系实现了100%的脱亚硝化；GSNO的产量低于预期，消耗的GSH量也低于预期。当将预期的100%产量浓度的GSNO应用于细胞溶胶孵育体系时，其中20 - 40%会迅速消失。亚硝化的蛋白质硫醇占释放的NO部分的35%，亚硝酸根离子占30%，并且可检测到一氧化氮的产生。与GSNO的消失同时，GSH和氧化型谷胱甘肽（GSSG）的生成量与在CyanoDMNG/GSH孵育体系中检测到的量相似。因此，GSNO在细胞溶胶中的去向决定了基于谷胱甘肽的产物的产量，并且证明了谷胱甘肽转移酶反应的化学计量关系。在由等摩尔的CyanoDMNG、GSH和NADPH组成的孵育体系中，脱亚硝化作用再次达到100%，但GSNO产量非常低，剩余的GSH增加。在含有预期100%产量浓度的GSNO的孵育体系中加入NADPH会导致GSNO迅速降解，产生GSH和一种可检测到但未鉴定的产物；S-亚硝化蛋白质、亚硝酸盐和硝酸盐的产量极少，一氧化氮的产生被消除，并且孵育体系对氯化汞/偶氮染料测定的反应接近零。目前尚不清楚这种GSNO分解代谢后NO部分的去向。
