In vitro and in vivo response of hepatocytes from hepatic nodules to the mitoinhibitory effects of phenobarbital.
In vitro and in vivo response of hepatocytes from hepatic nodules to the mitoinhibitory effects of phenobarbital.
复制标题
肝结节肝细胞对苯巴比妥有丝分裂抑制作用的体外和体内反应。
DOI：
10.1093/carcin/15.9.1963
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发表时间：
1994
期刊：
影响因子：
4.7
通讯作者：
Sarma,DS
中科院分区：
文献类型：
--
作者：
Manjeshwar,S;Laconi,E;Sheikh,A;Rao,PM;Rajalakshmi,S;Sarma,DS
苯巴比妥（PB）促进大鼠肝癌发生的拟议机制之一是差异性有丝分裂抑制。然而，我们早期的研究表明，PB抑制从周围非结节性肝和肝结节中分离的体外肝细胞的DNA合成由乳清酸（OA）促进。由于由一个启动子产生的结节不一定对另一个启动子具有抗性，因此进行本研究以确定由PB本身促进的病灶/结节是否对PB的有丝分裂抑制作用具有抗性。因此，大鼠开始与二乙基亚硝胺（DENA，200 mg/kg i. p.）和PB促进体外研究表明，PB（3-5 mM）抑制表皮生长因子（EGF）诱导的非结节性肝细胞以及PB促进的结节性肝细胞DNA合成33周。在另一项实验中，暴露于PB 33周的启动大鼠进行三分之二部分肝切除术（PH）或假肝切除术。用氚化胸苷体内标记肝细胞48 h。放射自显影分析表明，在PB存在下，病灶/结节和周围非结节性肝脏的肝细胞对PH的反应程度相同。此外，与相应的对照组相比，它们对PH的反应效率较低。此外，启动大鼠暴露于PB 16周后进行PH并在4周后处死，PB组中γ-谷氨酰转肽酶阳性病灶/结节所占面积百分比增加，但与未暴露于PB的启动对照大鼠相同。上述结果提出了一个有趣的可能性，即PB促进的结节对PB的有丝分裂抑制作用缺乏抗性可能是因为PB促进的结节不表达抗性表型。为了检验这一方面，检测了来自33周PB促进的结节的肝细胞对OA的有丝分裂抑制作用的反应。结果表明，OA（60-120 μM）抑制EGF诱导的肝细胞DNA合成，这些肝细胞分离自两个结节以及周围的非结节性肝。这些结果表明，PB是一个mitoinhibitor，但可能不会提供一个强大的差异生长优势，病灶/结节在增殖刺激。此外，PB促进的结节似乎不表达抗性表型，定义为对OA和PB的有丝分裂抑制作用具有抗性。
One of the proposed mechanisms by which phenobarbital (PB) promotes hepatocarcinogenesis in the rat is by differential mitoinhibition. However, our earlier studies indicated that PB inhibited DNA synthesisin vitroin hepatocytes isolated from both surrounding non-nodular liver and hepatic nodules promoted by orotic acid (OA). Since nodules generated by one promoter need not necessarily be resistant to another promoter, the present study was undertaken to determine whether foci/nodules promoted by PB itself are resistant to the mitoinhibitory effects of PB. Accordingly, rats were initiated with diethylnitrosamine (DENA, 200 mg/kg i.p) and promoted with PB (0.07% of PB as its sodium salt) in their drinking water for 16 or 33 weeks.In vitrostudies indicated that PB (3–5 mM) inhibited DNA synthesis induced by epidermal growth factor (EGF) in hepatocytes from surrounding non-nodular liver as well as from nodules promoted by PB for 33 weeks. In another experiment, initiated rats exposed to PB for 33 weeks were subjected to either two-thirds partial hepatectomy (PH) or sham hepatectomy. Hepatocytes were labelled with tritiated thymidine in vivo for 48 h. Autoradiographic analysis indicated that in the presence of PB, the hepatocytes from both foci/nodules and the surrounding non-nodular liver responded to PH to the same extent. In addition, they both responded to PH less efficiently as compared to the corresponding controls. Further, initiated rats exposed to PB for 16 weeks when subjected to PH and killed 4 weeks thereafter, the percentage area occupied by γ-glutamyl-transpeptidase-positive foci/nodules in the PB group increased, but to the same extent as in initiated control rats not exposed to PB. The above results raised an interesting possibility that the lack of resistance of the PB-promoted nodules to the mitoinhibitory effects of PB may be because the PB-promoted nodule does not express a resistant phenotype. To examine this aspect, the response of hepatocytes from 33 week PB-promoted nodules to the mitoinhibitory effects of OA was examined. The results indicated that OA (60–120 μM) inhibited EGF-induced DNA synthesis in hepatocytes isolated from both nodules as well as from surrounding non-nodular liver. These results suggest that PB is a mitoinhibitor but may not provide a strong differential growth advantage to foci/nodules in response to a proliferative stimulus. Further, the nodules promoted by PB do not appear to express the resistant phenotype, defined as being resistant to the mitoinhibitory effects of OA and PB.