Calcium as a permissive factor but not an initiation factor in DNA synthesis induction in cultured rat hepatocytes by the peroxisome proliferator ciprofibrate.
Calcium as a permissive factor but not an initiation factor in DNA synthesis induction in cultured rat hepatocytes by the peroxisome proliferator ciprofibrate.
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DOI：
10.1016/0006-2952(93)90612-z
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发表时间：
1993-12
影响因子：
5.8
通讯作者：
A. Bennett;G. Williams
中科院分区：
文献类型：
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作者：
A. Bennett;G. Williams
环丙贝特是一种非遗传毒性的肝癌原和过氧化物酶体增殖剂，在体内和培养的成年大鼠肝细胞中均为肝有丝分裂原，但其促有丝分裂的机制尚未阐明。我们以前观察到，环丙贝特迅速增加肝细胞内游离Ca 2+浓度（[Ca 2 +]i），表明这种作用可能在DNA合成的启动中发挥作用。在本研究中，我们已经确定了钙离子和环丙贝特刺激肝细胞DNA合成之间的关系。将培养的成年大鼠肝细胞暴露于环丙贝特（200 μM）48小时可使DNA合成增加约2倍，在钙缺乏培养基中以及钙通道阻断剂尼卡地平和维拉帕米可减弱该反应。为了研究环丙贝特刺激肝细胞DNA合成与[Ca ~（2+）] i升高之间的关系，采用细胞内Ca ~（2+）螯合剂5，5 ′-二甲基-1，2-双（2-氨基苯氧基乙烷）-N，N，N′，N′-四乙酸（dimethyl-BAPTA）。用二甲基-BAPTA预处理肝细胞可阻断环丙贝特诱导的[Ca ~（2+）] i升高，但不能阻断环丙贝特诱导的肝细胞DNA合成。二甲基-BAPTA仅在48小时培养期的后24小时期间存在时有效减少环丙贝特诱导的DNA合成。这些数据表明，肝细胞[Ca 2 +] i的早期动员环丙贝特不起启动作用，在诱导肝细胞DNA合成，而是可能作为一个允许的因素进入环丙贝特处理的成年大鼠肝细胞进入S期。
The non-genotoxic hepatocarcinogen and peroxisome proliferating agent, ciprofibrate, is a liver mitogen bothin vivoand in cultured adult rat hepatocytes, but the mechanisms of its mitogenicity have not been elucidated. We previously observed that ciprofibrate rapidly increased hepatocyte free intracellular Ca2+concentration ([Ca2+]i), suggesting that this effect may play a role in the initiation of DNA synthesis. In the present study, we have identified a relationship between Ca2+and the stimulation of hepatocyte DNA synthesis by ciprofibrate. Exposure of cultured adult rat hepatocytes to ciprofibrate (200 μM) for 48 hr increased DNA synthesis by approximately 2-fold, and this response was attenuated in a Ca2+-deficient medium and by the Ca2+channel blockers nicardipine and verapamil. To examine the relationship between the stimulation of hepatocyte DNA synthesis and increases in [Ca2+]iby ciprofibrate, the intracellular Ca2+chelator 5,5′-dimethyl-1,2-bis(2-aminophenoxyethane)-N,N,N′,N′-tetraacetic acid (dimethyl-BAPTA) was employed. Pretreatment of hepatocytes with dimethyl-BAPTA blocked ciprofibrate-induced [Ca2+]iincrease, but did not block ciprofibrate-induced hepatocyte DNA synthesis. Dimethyl-BAPTA was only effective in reducing ciprofibrate-induced DNA synthesis when present during the latter 24 hr of a 48-hr cultured period. These data suggest that the early mobilization of hepatocyte [Ca2+]iby ciprofibrate does not play an initiating role in the induction of hepatocyte DNA synthesis but rather may operate as a permissive factor for the entry of ciprofibrate-treated adult rat hepatocytes into S-phase.