Hasspieler B M, Di Giulio R T
Ecotoxicology Laboratory, School of the Environment, Duke University, Durham, North Carolina 27706.
Toxicol Appl Pharmacol. 1992 May;114(1):156-61. doi: 10.1016/0041-008x(92)90108-5.
Characteristics of DT diaphorase (NAD(P)H: (quinone acceptor) oxidoreductase, DTD) activity in Ictalurus punctatus and the effect of DTD activity on menadione (MND)-mediated reduction of acetylated cytochrome c (AcC) were examined. DTD activity in cytosols of four organs followed a distinct gradient in the order stomach greater than gill greater than liver greater than posterior kidney. A similar gradient was observed in organ-specific rates of in vitro AcC reduction in the presence of either NADH or NADPH as reducing equivalent. A greater proportion of the AcC reduction rate was sensitive to inhibition by dicoumarol (DC) in organs with relatively high DTD specific activity (e.g., stomach) than in organs with low DTD activity (e.g., kidney). No such trend was observed in the superoxide dismutase (SOD)-sensitive proportion of AcC reduction rates. DTD was observed to contribute to MND-mediated superoxide production to a greater extent in organs with high DTD activity than in organs with low DTD activity. DC-sensitive (i.e., DTD-mediated) AcC reduction was observed to increase with organ-specific DTD activity, and the majority of the AcC reduction rate was inhibitable by SOD. These findings demonstrate a direct contribution by DTD activity to MND-mediated superoxide production in this in vitro system. The role of I. punctatus DTD as a possible deleterious agent in quinone metabolism and implications regarding the traditional conception of DTD as a detoxifying enzyme are discussed.
研究了斑点叉尾鮰中DT黄递酶（NAD(P)H：（醌受体）氧化还原酶，DTD）的活性特征以及DTD活性对甲萘醌（MND）介导的乙酰化细胞色素c（AcC）还原的影响。四个器官胞质溶胶中的DTD活性呈现出明显的梯度，顺序为胃＞鳃＞肝脏＞后肾。在以NADH或NADPH作为还原当量的情况下，体外AcC还原的器官特异性速率也观察到类似的梯度。与DTD活性较低的器官（如肾脏）相比，在DTD比活性相对较高的器官（如胃）中，更大比例的AcC还原速率对双香豆素（DC）抑制敏感。在AcC还原速率对超氧化物歧化酶（SOD）敏感的比例方面未观察到这种趋势。观察到在DTD活性高的器官中，DTD对MND介导的超氧化物产生的贡献程度大于DTD活性低的器官。观察到DC敏感的（即DTD介导的）AcC还原随着器官特异性DTD活性的增加而增加，并且大部分AcC还原速率可被SOD抑制。这些发现证明了在该体外系统中，DTD活性对MND介导的超氧化物产生有直接贡献。讨论了斑点叉尾鮰DTD作为醌代谢中可能的有害剂的作用以及关于DTD作为解毒酶的传统观念的影响。
