EFFECTS OF EXTRACELLULAR AND INTRACELLULAR PH ON REPAIR OF POTENTIALLY LETHAL DAMAGE, CHROMOSOME-ABERRATIONS AND DNA DOUBLE-STRAND BREAKS IN IRRADIATED PLATEAU-PHASE A549 CELLS
EFFECTS OF EXTRACELLULAR AND INTRACELLULAR PH ON REPAIR OF POTENTIALLY LETHAL DAMAGE, CHROMOSOME-ABERRATIONS AND DNA DOUBLE-STRAND BREAKS IN IRRADIATED PLATEAU-PHASE A549 CELLS
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DOI：
10.2307/3578659
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发表时间：
1994-08-01
影响因子：
3.4
通讯作者：
VARNES, ME
中科院分区：
文献类型：
--
作者：
JAYANTH, VR;BAYNE, MT;VARNES, ME
平台期A549细胞表现出高的修复Df潜在致死性辐射损伤（PLD）的能力。以前发现，PLD修复可以通过在辐射后保持期间将用过的培养基的细胞外pH（pH（e））从其正常值6.7-6.8增加到7.6来部分抑制。目前的研究表明，PLD修复也被抑制，通过降低废培养基的pH值（e）到6.0。研究了改变pH（e）对通过中性滤膜洗脱测量的DNA双链断裂（DSB）重新连接以及从平台期释放细胞后观察到的有丝分裂延迟和染色体畸变的影响。无论是增加还是降低废培养基的pH值（e）对辐射诱导的有丝分裂延迟都没有影响。在pH（e）6.0下保持可显著抑制DSB的再连接，但在pH（e）7.6下保持不影响DSB的再连接。在照射后2小时，在pH（e）6.0下约有51%的未连接断裂保留，而在pH（e）6.7或7.6下约有15%。然而，保持在pH（e）7.6似乎引起DSB重新连接的动力学的边际变化。当细胞保持在pH（e）6.0时，不会发生导致双着丝粒和无着丝粒染色体畸变的病变修复，因为在传代培养前保持24 h的细胞中，这些畸变消失的不到10%。相比之下，将平台期细胞保持在pH（e）7.6 vs 6.7，导致双着丝粒消失的小但显著的减少，但对无着丝粒消失的速率或程度没有影响。这些数据使我们推测，通过保持在pH（e）6.0抑制PLD修复与pH依赖性DNA修复酶的抑制和当细胞从平台期释放时导致错误修复的DNA变化的诱导有关。另一方面，通过保持在pH（e）7.6抑制PLD修复主要与促进错误修复的DNA结构的变化有关。
Plateau-phase A549 cells exhibit a high capacity for repair Df potentially lethal radiation damage (PLD). Previously it was found that PLD repair could be partially inhibited by increasing the extracellular pH (pH(e)) of the spent medium from its normal value of 6.7-6.8 to 7.6 during postirradiation holding. The present study shows that PLD repair is also inhibited by reducing the pH(e) of the spent medium to 6.0. The effects of altering pH(e) on rejoining of DNA double-strand breaks (DSBs) as measured by neutral filter elution and on mitotic delay and chromosome aberrations seen after releasing cells from the plateau phase were investigated. Neither increasing nor decreasing the pH(e) of the spent medium had an effect on radiation-induced mitotic delay. Rejoining of DSBs was significantly inhibited by holding at pH(e) 6.0 but not affected by holding at pH(e) 7.6. At 2 h after irradiation about 51% of unrejoined breaks remained at pH(e) 6.0, compared to about 15% at pH(e) 6.7 or 7.6. However, holding at pH(e) 7.6 appeared to cause a marginal change in the kinetics of rejoining of DSBs. Repair of lesions leading to dicentric and acentric chromosome aberrations did not occur when cells were held at pH(e) 6.0, since less than 10% of these aberrations disappeared from cells held for 24 h before subculture. In contrast, holding plateau-phase cells at pH(e), 7.6 vs 6.7 caused a small but significant reduction in the disappearance of dicentrics but had no effect on the rate or extent of the disappearance of acentrics. These data have led us to hypothesize that inhibition of PLD repair by holding at pH(e) 6.0 is related both to inhibition of pH-dependent DNA repair enzymes and to induction of changes in DNA which lead to misrepair when the cells are released from plateau phase. Inhibition of PLD repair by holding at pH(e), 7.6, on the other hand, is related primarily to changes in DNA structure which promote misrepair.