Srivastava M, Kale R K
Free Radical Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi-110 067, India.
Radiat Res. 1999 Sep;152(3):257-64.
The xanthine oxidoreductase system is one of the major sources of free radicals in many pathophysiological conditions. Since ionizing radiations cause cell damage and death, the xanthine oxidoreductase system may contribute to the detrimental effects in irradiated systems. Therefore, modulation of the xanthine oxidoreductase system by radiation has been examined in the present study. Female Swiss albino mice (7-8 weeks old) were irradiated with gamma rays (1-9 Gy) at a dose rate of 0.023 Gy s(-1) and the specific activities of xanthine oxidase (XO) and xanthine dehydrogenase (XDH) were determined in the liver of the animals. The mode and magnitude of change in the specific activities of XO and XDH were found to depend on radiation dose. At doses above 3 Gy, the specific activity of XO increased rapidly and continued to increase with increasing dose. However, the specific activity of XDH was decreased. These findings are suggestive of an inverse relationship between the activity of XO and XDH. The ratio of the activity of XDH to that of XO decreased with radiation dose. However, the total activity (XDH + XO) remained constant at all doses. These results indicate that XDH may be converted into XO. An intermediate form, D/O, appears to be transient in the process of conversion. The enhanced specific activity of XO may cause oxidative stress that contributes to the radiation damage and its persistence in the postirradiation period. Radiation-induced peroxidative damage determined in terms of the formation of TBARS and the change in the specific activity of lactate dehydrogenase support this possibility.
黄嘌呤氧化还原酶系统是许多病理生理状况下自由基的主要来源之一。由于电离辐射会导致细胞损伤和死亡，黄嘌呤氧化还原酶系统可能会促使受辐照系统产生有害影响。因此，本研究检测了辐射对黄嘌呤氧化还原酶系统的调节作用。选用7 - 8周龄的雌性瑞士白化小鼠，以0.023 Gy s(-1)的剂量率用γ射线（1 - 9 Gy）进行辐照，然后测定动物肝脏中黄嘌呤氧化酶（XO）和黄嘌呤脱氢酶（XDH）的比活性。发现XO和XDH比活性的变化方式和幅度取决于辐射剂量。在3 Gy以上的剂量时，XO的比活性迅速增加，并随着剂量增加持续升高。然而，XDH的比活性降低。这些发现表明XO和XDH的活性之间存在负相关关系。XDH与XO活性的比值随辐射剂量降低。然而，总活性（XDH + XO）在所有剂量下均保持恒定。这些结果表明XDH可能会转化为XO。一种中间形式，即D/O，在转化过程中似乎是短暂的。XO比活性的增强可能会导致氧化应激，从而导致辐射损伤及其在辐照后阶段的持续存在。以丙二醛的形成和乳酸脱氢酶比活性的变化来衡量的辐射诱导的过氧化损伤支持了这种可能性。
