Pekala P H, Lane M D, Watkins P A, Moss J
J Biol Chem. 1981 May 25;256(10):4871-6.
Differentiation of 3T3-L1 preadipocytes, induced by methylisobutylxanthine (MIX), dexamethasone (DEX), and insulin, produces cells with the morphological and biochemical characteristics of adipocytes. Poly(ADP-ribose) synthetase activity in 3T3-L1 cells treated with MIX, DEX, and insulin underwent an abrupt decrease in activity, remained low for several hours, and then increased; this rise was delayed by readdition of MIX, DEX, and insulin. The drop of synthetase activity represents the earliest alteration of a specific enzyme yet detected during the differentiation of 3T3-L1 cells. Nondifferentiating 3T3-C2 control cells do not exhibit changes in poly(ADP-ribose) synthetase activity when treated with MIX, DEX, and insulin. The transient reduction in poly(ADP-ribose) synthetase activity in 3T3-L1 cells occurred prior to the appearance of the adipocyte phenotype induced by the above agents and was not observed when preparations were assayed in the presence of DNase I. It is evident that poly(ADP-ribose) synthetase activity was masked following treatment with MIX, DEX, and insulin since the synthetase is sensitive to agents that affect the physical properties of DNA. This transient reduction in activity may be an early event in differentiation which reflects changes in chromatin structure.
用甲基异丁基黄嘌呤（MIX）、地塞米松（DEX）和胰岛素诱导3T3-L1前脂肪细胞分化，可产生具有脂肪细胞形态和生化特征的细胞。用MIX、DEX和胰岛素处理的3T3-L1细胞中的聚（ADP-核糖）合成酶活性经历了活性的突然下降，在数小时内保持较低水平，然后升高；重新添加MIX、DEX和胰岛素会延迟这种升高。合成酶活性的下降代表了在3T3-L1细胞分化过程中迄今检测到的特定酶的最早变化。未分化的3T3-C2对照细胞在用MIX、DEX和胰岛素处理时，聚（ADP-核糖）合成酶活性没有变化。3T3-L1细胞中聚（ADP-核糖）合成酶活性的短暂降低发生在上述试剂诱导的脂肪细胞表型出现之前，并且在存在DNA酶I的情况下检测制剂时未观察到这种降低。很明显，在用MIX、DEX和胰岛素处理后，聚（ADP-核糖）合成酶活性被掩盖了，因为该合成酶对影响DNA物理性质的试剂敏感。这种活性的短暂降低可能是分化过程中的早期事件，反映了染色质结构的变化。
