Role of transiently altered sarcolemmal membrane permeability and basic fibroblast growth factor release in the hypertrophic response of adult rat ventricular myocytes to increased mechanical activity in vitro
Role of transiently altered sarcolemmal membrane permeability and basic fibroblast growth factor release in the hypertrophic response of adult rat ventricular myocytes to increased mechanical activity in vitro
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DOI：
10.1172/jci118414
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发表时间：
1996-01-15
影响因子：
15.9
通讯作者：
Kelly, RA
中科院分区：
文献类型：
--
作者：
Kaye, D;Pimental, D;Kelly, RA
在几种组织和细胞类型中，碱性成纤维细胞生长因子(碱性成纤维细胞生长因子；虽然哺乳动物心肌细胞表达bFGF，但目前尚不清楚它是否在介导心脏对增加的负荷的适应中发挥作用，也不知道胞浆18-kD亚型bFGF的释放如何在增加的机械应力下调节。为了检验机械活动增加导致肌膜通透性的瞬时变化从而允许胞浆bFGF释放并随后作为自分泌和旁分泌生长刺激的假说，我们研究了在无血清、限定的培养液中维持的成年大鼠心室肌细胞的原代分离，这些细胞以3赫兹的频率连续起搏长达5天。表现为“肥大”反应，其特征是苯丙氨酸掺入速率、细胞总蛋白含量和细胞大小增加。这些变化可以通过外源重组bFGF在对照细胞中模拟，并可以在持续起搏的细胞中被特定的中和性抗bFGF抗体阻断。此外，通过监测10-kD葡聚糖结合荧光素对心肌细胞的摄取率，检测到持续起搏的心肌细胞条件培养液中含有显著更多的碱性成纤维细胞生长因子和3T3细胞的有丝分裂活性，这一活性可以被中和的抗bFGF抗体降低，通过监测起搏心肌细胞摄取荧光素标记的葡聚糖的速率，检验了起搏心肌细胞发生足以允许胞浆碱性成纤维细胞生长因子释放的一过性膜破坏的假说，这些数据与肌膜通透性的非致死性、一过性改变和胞液bFGF释放是导致心肌细胞肥大反应的一种机制相一致。
One of the trophic factors that has been implicated in initiating or facilitating growth in response to increased mechanical stress in several tissues and cell types is basic fibroblast growth factor (bFGF; FGF-2), Although mammalian cardiac muscle cells express bFGF, it is not known whether it plays a role in mediating cardiac adaptation to increased load, nor how release of the cytosolic 18-kD isoform of bFGF would be regulated in response to increased mechanical stress, To test the hypothesis that increased mechanical activity induces transient alterations in sarcolemmal permeability that allow cytosolic bFGF to be released and subsequently to act as an autocrine and paracrine growth stimulus, we examined primary isolates of adult rat ventricular myocytes maintained in serum-free, defined medium that were continually paced at 3 Hz for up to 5 d. Paced myocytes, but not nonpaced control cells, exhibited a ''hypertrophic'' response, which was characterized by increases in the rate of phenylalanine incorporation, total cellular protein content, and cell size. These changes could be mimicked in control cells by exogenous recombinant bFGF and could be blocked in continually paced cells by a specific neutralizing anti-bFGF antibody. In addition, medium conditioned by continually paced myocytes contained Significantly more bFGF measured by ELISA and more mitogenic activity for 3T3 cells, activity that could be reduced by a neutralizing anti-bFGF antibody, The hypothesis that transient membrane disruptions sufficient to allow release of cytosolic bFGF occur in paced myocytes was examined by monitoring the rate of uptake into myocytes from the medium of 10-kD dextran linked to fluorescein, Paced myocytes exhibited a significantly higher rate of fluorescein-labeled dextran uptake, These data are consistent with the hypothesis that nonlethal, transient alterations in sarcolemmal membrane permeability with release of cytosolic bFGF is one mechanism by which increased mechanical activity could lead to a hypertrophic response in cardiac myocytes.