Hayasaki-Kajiwara Y, Kitano Y, Iwasaki T, Shimamura T, Naya N, Iwaki K, Nakajima M
Discovery Research Laboratories, Shionogi & Co Ltd, 3-1-1 Futaba-cho, Toyonaka, Osaka, 561-0825, Japan.
J Mol Cell Cardiol. 1999 Aug;31(8):1559-72. doi: 10.1006/jmcc.1999.0993.
Protein kinase C (PKC) is one of the important signaling molecules in the development of the cardiac hypertrophic response, and activation of Na(+)/H(+)exchange is caused by PKC in myocytes. In this study we examined the contribution of Na(+)/H(+)exchange in cardiac hypertrophy induced by the activation of PKC and its mechanism using cultured neonatal rat cardiac myocytes. Phenylephrine (PE), endothelin-1 (ET-1) and phorbol 12-myristate 13-acetate (PMA) increased cytoplasmic pH in myocytes, and this effect was strongly inhibited by treatment with HOE694, an inhibitor of Na(+)/H(+)exchange. These substances increased the [(3)H]phenylalanine incorporation, total protein content and beta -myosin heavy chain protein content in myocytes. These hypertrophic responses were also attenuated by HOE694. To clarify the role of Na(+)influx through activation of Na(+)/H(+)exchange in cardiac hypertrophy, we next examined the hypertrophic responses to veratridine and ouabain, which increase the intracellular Na(+)content. Veratridine and ouabain increased the [(3)H]phenylalanine incorporation. Staurosporine, a PKC inhibitor, completely abolished veratridine-induced hypertrophic response, but did not affect increment of intracellular Na(+)concentration by veratridine. PMA caused increases of alpha -, delta -and epsilon -PKC in the particulate fraction, but PE, ET-1 and veratridine affected only those of delta - and epsilon -PKC. HOE694 significantly inhibited only increases of delta - and epsilon -PKC caused by PE, ET-1 or PMA, but not those by veratridine. These results demonstrate that Na(+)influx via activation of Na(+)/H(+)exchange reactivates PKC in myocytes. delta - and epsilon -PKC appear to be involved in the signal mechanism of the hypertrophic response induced by Na(+)influx through Na(+)/H(+)exchange in myocytes.
蛋白激酶C（PKC）是心脏肥厚反应发生过程中的重要信号分子之一，PKC可引起心肌细胞中Na(+)/H(+)交换的激活。在本研究中，我们利用培养的新生大鼠心肌细胞，研究了Na(+)/H(+)交换在PKC激活诱导的心脏肥厚中的作用及其机制。去甲肾上腺素（PE）、内皮素-1（ET-1）和佛波酯（PMA）可使心肌细胞内的pH值升高，而Na(+)/H(+)交换抑制剂HOE694可强烈抑制这一效应。这些物质可增加心肌细胞中[(3)H]苯丙氨酸的掺入量、总蛋白含量和β-肌球蛋白重链蛋白含量。HOE694也可减弱这些肥厚反应。为了阐明通过激活Na(+)/H(+)交换使Na(+)内流在心脏肥厚中的作用，我们接下来研究了对藜芦碱和哇巴因的肥厚反应，这两种物质可增加细胞内Na(+)含量。藜芦碱和哇巴因可增加[(3)H]苯丙氨酸的掺入量。PKC抑制剂星形孢菌素可完全消除藜芦碱诱导的肥厚反应，但不影响藜芦碱引起的细胞内Na(+)浓度升高。PMA可使颗粒部分的α-PKC、δ-PKC和ε-PKC增加，但PE、ET-1和藜芦碱仅影响δ-PKC和ε-PKC。HOE694仅显著抑制PE、ET-1或PMA引起的δ-PKC和ε-PKC增加，而不抑制藜芦碱引起的增加。这些结果表明，通过激活Na(+)/H(+)交换使Na(+)内流可使心肌细胞中的PKC重新激活。δ-PKC和ε-PKC似乎参与了通过Na(+)/H(+)交换使Na(+)内流诱导的肥厚反应的信号机制。
