Martinez R, Gillies R J, Giuliano K A
Department of Biochemistry, Colorado State University, Fort Collins 80523.
J Cell Physiol. 1988 Jul;136(1):154-60. doi: 10.1002/jcp.1041360120.
One of the earliest responses of quiescent mammalian cells to the addition of serum is an increase in intracellular pH (pHin). This pHin change is generally believed to be due to an increased activity of Na+/H+ exchange. A number of investigators have observed steady-state differences in pHin between cells in the presence and absence of serum. However, no one has examined differences in pHin regulation that may exist between cells chronically exposed to, or deprived of serum. In this study, we investigated the effects of serum deprivation to identify those components of pHin regulation that were associated with quiescence. To do this, we examined pHin in cells growing chronically in 10% serum as well as in cells that were either acutely (1.5-2 hr) or chronically (48 hr) deprived of serum. Intracellular pH was monitored using the fluorescence of intracellularly loaded pyranine dye. Our results indicate that the resting pHin values of chronically or acutely serum-deprived cells were not significantly different from each other yet, in both cases, were lower than those observed in cells exposed to 10% serum. Furthermore, we observed significant increases in pHin of both acutely or chronically serum-deprived cells in response to the addition of serum at various concentrations, in the presence of 24 mM bicarbonate. Chronically serum-deprived cells had slightly smaller responses and were more sensitive to lower concentrations of serum than were acutely deprived cells. Therefore, our data suggest that long-term serum deprivation affects the magnitude and sensitivity of pHin to serum stimulation and causes the loss of some form of pHin regulatory mechanism(s).
静止的哺乳动物细胞对添加血清的最早反应之一是细胞内pH值（pHin）升高。普遍认为这种pHin变化是由于Na+/H+交换活性增加所致。许多研究人员观察到在有血清和无血清情况下细胞的pHin存在稳态差异。然而，没有人研究过长期暴露于血清或血清剥夺的细胞之间可能存在的pHin调节差异。在本研究中，我们调查了血清剥夺的影响，以确定与静止相关的pHin调节成分。为此，我们检测了长期在10%血清中生长的细胞以及急性（1.5 - 2小时）或慢性（48小时）血清剥夺细胞的pHin。使用细胞内加载的吡喃染料荧光监测细胞内pH值。我们的结果表明，慢性或急性血清剥夺细胞的静息pHin值彼此之间无显著差异，但在这两种情况下，均低于暴露于10%血清的细胞所观察到的值。此外，我们观察到在24 mM碳酸氢盐存在下，急性或慢性血清剥夺细胞在添加不同浓度血清后pHin均显著升高。慢性血清剥夺细胞的反应略小，且比急性剥夺细胞对较低浓度血清更敏感。因此，我们的数据表明，长期血清剥夺会影响pHin对血清刺激的幅度和敏感性，并导致某种形式的pHin调节机制丧失。
