Ishizuka J, Bold R J, Townsend C M, Thompson J C
Department of Surgery, University of Texas Medical Branch, Galveston 77555.
Cancer Invest. 1995;13(2):181-7. doi: 10.3109/07357909509011688.
Activity of ornithine decarboxylase (ODC), one of the rate-limiting enzymes in the pathway of polyamine biosynthesis, is regulated by various factors. In this study, we examined the role of Ca2+ in the regulation of ODC enzyme activity in mouse colon cancer cells (MC-26). KCl, a membrane-depolarizing agent that opens the voltage-dependent Ca(2+)-channel to increase intracellular Ca2+, decreased serum-induced ODC enzyme activity in MC-26 cells in a dose-dependent, reversible fashion. Both verapamil and nifedipine, inhibitors of the L-type voltage-dependent Ca(2+)-channel, decreased serum-induced ODC enzyme activity. W-7, a calmodulin inhibitor, decreased ODC enzyme activity in a dose-dependent, reversible fashion while trifluoperazine, another calmodulin inhibitor, failed to affect ODC enzyme activity in MC-26 cells. Our findings indicate that intracellular Ca2+ participates in the regulatory mechanism of ODC enzyme activity in MC-26 cells, although the exact role of Ca2+ is still unclear.
鸟氨酸脱羧酶（ODC）是多胺生物合成途径中的限速酶之一，其活性受多种因素调节。在本研究中，我们检测了Ca2+在小鼠结肠癌细胞（MC-26）中对ODC酶活性调节的作用。KCl是一种使膜去极化的试剂，可打开电压依赖性Ca(2+)通道以增加细胞内Ca2+，它能以剂量依赖性、可逆的方式降低血清诱导的MC-26细胞中的ODC酶活性。维拉帕米和硝苯地平这两种L型电压依赖性Ca(2+)通道抑制剂，均可降低血清诱导的ODC酶活性。钙调蛋白抑制剂W-7能以剂量依赖性、可逆的方式降低ODC酶活性，而另一种钙调蛋白抑制剂三氟拉嗪则未能影响MC-26细胞中的ODC酶活性。我们的研究结果表明，细胞内Ca2+参与了MC-26细胞中ODC酶活性的调节机制，尽管Ca2+的确切作用仍不清楚。
