Denisenko M F, Soldatenkov V A, Belovskaia L N, Filippovich I V
Radiobiologiia. 1988 Jan-Feb;28(1):19-23.
The diminution of NAD level in mouse thymus lymphocytes precedes their death under the effect of various genotoxic agents and manifests itself by the time of the onset of chromatin degradation. At the same time, in vitro, NAD does not influence the activity of micrococcus nuclease of Ca2+,Mg2+-dependent endonuclease from human spleen. Stimulation of protein poly(ADP-ribosylation) by exogenous NAD does not change the sensitivity of chromatin to micrococcus nuclease. In contrast to hepatocytes, in the thymus, no inhibition of Ca2+,Mg2+-endonuclease, resulting from ADP-ribosylation, occurs which may be due to low activity of ADP-ribosyl transferase in thymocytes. Incubation of thymus lymphocytes with benzamide prior to irradiation does not inhibit chromatin degradation. It is suggested that the decrease in the NAD level is one of the indications of the injury to thymocytes which is not related to the induction of their death. In contrast to thymocytes, the pretreatment of Ehrlich ascites tumor cells with benzamide produces a radiosensitizing effect.
在各种基因毒性剂的作用下，小鼠胸腺淋巴细胞中NAD水平的降低先于其死亡，并在染色质降解开始时表现出来。同时，在体外，NAD不影响来自人脾脏的Ca2+、Mg2+依赖性核酸内切酶的微球菌核酸酶活性。外源性NAD对蛋白质多聚（ADP-核糖基化）的刺激不会改变染色质对微球菌核酸酶的敏感性。与肝细胞不同，在胸腺中，不会发生由ADP-核糖基化引起的对Ca2+、Mg2+ - 核酸内切酶的抑制，这可能是由于胸腺细胞中ADP-核糖基转移酶的活性较低。在照射前用苯甲酰胺孵育胸腺淋巴细胞不会抑制染色质降解。有人认为，NAD水平的降低是胸腺细胞损伤的指标之一，这与诱导其死亡无关。与胸腺细胞不同，用苯甲酰胺预处理艾氏腹水肿瘤细胞会产生放射增敏作用。
