Gillies R J, Deamer D W
J Cell Physiol. 1980 Nov;105(2):221-5. doi: 10.1002/jcp.1041050205.
Media concentration of total soluble CO2 increases with culture age of Tetrahymena pyriformis. CO2 is a weak acid and is capable of acidifying intracellular pH (pHi). Changes in pHi have been demonstrated to affect cell metabolism and growth in many systems. For these reasons, we investigated whether the concentrations of CO2 produced in vitro were sufficient to affect cell proliferation and pHi in Tetrahymena. In this study, we used DMO to mimic the weak acid properties of CO2. DMO is freely permeable to membranes in its uncharged form and has a pKa similar to that of CO2/HCO3(-). In addition, it has the advantages of being metabolically inert and non-volatile. At concentrations similar to endogenously produced CO2, DMO acidifies pHi and arrests culture growth. In addition, procedures are described which decrease the media CO2 concentrations in both growing and non-growing cultures. These conditions lead to increased maximum culture density at stationary phase. The data indicate that, under our conditions, accumulation of CO2 in the culture leads to cessation of growth, probably through elimination of transmembrane pH gradients, which are necessary for regulation of metabolism and growth.
梨形四膜虫培养物中总可溶性二氧化碳的培养基浓度随培养时间增加。二氧化碳是一种弱酸，能够酸化细胞内pH值（pHi）。在许多系统中，已证明pHi的变化会影响细胞代谢和生长。基于这些原因，我们研究了体外产生的二氧化碳浓度是否足以影响梨形四膜虫的细胞增殖和pHi。在本研究中，我们使用二甲基氧乙酸（DMO）来模拟二氧化碳的弱酸性质。DMO以不带电荷的形式可自由透过细胞膜，其pKa与二氧化碳/碳酸氢根（-）的pKa相似。此外，它具有代谢惰性和不挥发的优点。在与内源性产生的二氧化碳相似浓度下，DMO会酸化pHi并阻止培养物生长。此外，还描述了降低生长和非生长培养物中培养基二氧化碳浓度的方法。这些条件导致稳定期的最大培养密度增加。数据表明，在我们的条件下，培养物中二氧化碳的积累可能通过消除调节代谢和生长所必需的跨膜pH梯度导致生长停止。
