Tokumura A, Okuno M, Fukuzawa K, Houchi H, Oka M
Faculty of Pharmaceutical Sciences, University of Tokushima, Japan.
J Lipid Mediat Cell Signal. 1996 Sep;14(1-3):127-35. doi: 10.1016/0929-7855(96)00518-4.
We found that lysophosphatidic acid (LPA) exerted two effects on Ca(2+)-movement in cultured bovine adrenal chromaffin cells. At concentrations of above 10(-5) M, it induced slight, but significant 45Ca2+ influx, resulting in release of a small portion of stored catecholamine. At high concentrations it also significantly increased the intracellular Ca2+ concentration in Fura-2-loaded cells. At concentrations as low as 10(-7) M, it stimulated extracellular Na(+)-dependent 45Ca2+ efflux, possibly by increasing Na+/Ca2+ exchange. The maximal efflux of Ca2+ attained with 10(-5) M LPA was inhibited by tyrosine kinase inhibitors, but augmented by a protein kinase C inhibitor. These results suggest that LPA-induced Ca2+ efflux is controlled positively and negatively by mechanisms involving tyrosine kinase and protein kinase C, respectively.
我们发现溶血磷脂酸（LPA）对培养的牛肾上腺嗜铬细胞中的Ca(2+)移动有两种作用。在浓度高于10(-5) M时，它诱导轻微但显著的45Ca2+内流，导致一小部分储存的儿茶酚胺释放。在高浓度时，它还显著增加了用Fura-2加载的细胞内的Ca2+浓度。在低至10(-7) M的浓度下，它刺激细胞外Na(+)-依赖的45Ca2+外流，可能是通过增加Na+/Ca2+交换实现的。10(-5) M LPA所达到的Ca2+最大外流被酪氨酸激酶抑制剂抑制，但被蛋白激酶C抑制剂增强。这些结果表明，LPA诱导的Ca2+外流分别受到涉及酪氨酸激酶和蛋白激酶C的机制的正向和负向控制。
