Martinez R, Gillies R J
Department of Biochemistry, Colorado State University, Fort Collins 80523.
J Cell Physiol. 1989 Apr;139(1):131-5. doi: 10.1002/jcp.1041390119.
In a companion paper (Gillies et al.: J. Cell. Physiol. 139:124-129, 1989) we show that phorbol esters (PEs) are unable to stimulate Na+/H+ exchange in BALB/c-3T3 cells under a wide variety of conditions. The Na+/H+ exchangers of a number other cell types are also not responsive to PEs yet have been rendered responsive by treatment with agents such as dimethylsulfoxide (DMSO). We undertook the present study to evaluate whether or not the treatment of BALB/c-3T3 cells with DMSO will induce modifications in the sensitivity of these cells to activation by PEs. The present study indicates that a 3-5 day exposure of BALB/c-3T3 cells to 1.25% DMSO leads to changes in the sensitivity of these cells to the activation of Na+/H+ exchanger by PEs. These changes in sensitivity were apparent at day 3 and maximal at day 5. Non-tumor-promoting analogues of PEs do not activate Na+/H+ exchange, suggesting that the effect is mediated through kinase C. Sphingosine prevents PE-, but not serum-induced alkalinization. However, the half-time of the intracellular pH (pHin) response to serum was increased by sphingosine, suggesting that kinase C participates in, but is not required for, the serum induced activation. Since DMSO does not induce any apparent morphological change, the change in sensitivity of Na+/H+ exchange to PEs is not likely to be related to differentiation, but may be associated with structural changes in the Na+/H+ exchanger and/or changes in isoforms of kinase C which recognize the exchanger as a substrate.
在一篇配套论文中（吉利斯等人：《细胞生理学杂志》139:124 - 129，1989年），我们表明佛波酯（PEs）在多种条件下均无法刺激BALB/c - 3T3细胞中的Na⁺/H⁺交换。许多其他细胞类型的Na⁺/H⁺交换体对PEs也无反应，但用二甲基亚砜（DMSO）等试剂处理后则变得有反应。我们开展本研究以评估用DMSO处理BALB/c - 3T3细胞是否会诱导这些细胞对PEs激活的敏感性发生改变。本研究表明，将BALB/c - 3T3细胞暴露于1.25%的DMSO中3 - 5天会导致这些细胞对PEs激活Na⁺/H⁺交换体的敏感性发生变化。这些敏感性变化在第3天明显，在第5天达到最大。PEs的非促肿瘤类似物不会激活Na⁺/H⁺交换，这表明该效应是通过蛋白激酶C介导的。鞘氨醇可阻止PEs诱导的碱化，但不能阻止血清诱导的碱化。然而，鞘氨醇增加了细胞内pH（pHin）对血清反应的半衰期，这表明蛋白激酶C参与了血清诱导的激活，但并非必需。由于DMSO不会诱导任何明显的形态变化，Na⁺/H⁺交换对PEs敏感性的变化不太可能与分化有关，而可能与Na⁺/H⁺交换体的结构变化和/或将该交换体识别为底物的蛋白激酶C同工型的变化有关。
