Boron Walter F
Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8026, USA.
Adv Physiol Educ. 2004 Dec;28(1-4):160-79. doi: 10.1152/advan.00045.2004.
The approach that most animal cells employ to regulate intracellular pH (pH(i)) is not too different conceptually from the way a sophisticated system might regulate the temperature of a house. Just as the heat capacity (C) of a house minimizes sudden temperature (T) shifts caused by acute cold and heat loads, the buffering power (beta) of a cell minimizes sudden pH(i) shifts caused by acute acid and alkali loads. However, increasing C (or beta) only minimizes T (or pH(i)) changes; it does not eliminate the changes, return T (or pH(i)) to normal, or shift steady-state T (or pH(i)). Whereas a house may have a furnace to raise T, a cell generally has more than one acid-extruding transporter (which exports acid and/or imports alkali) to raise pH(i). Whereas an air conditioner lowers T, a cell generally has more than one acid-loading transporter to lower pH(i). Just as a house might respond to graded decreases (or increases) in T by producing graded increases in heat (or cold) output, cells respond to graded decreases (or increases) in pH(i) with graded increases (or decreases) in acid-extrusion (or acid-loading) rate. Steady-state T (or pH(i)) can change only in response to a change in chronic cold (or acid) loading or chronic heat (or alkali) loading as produced, for example, by a change in environmental T (or pH) or a change in the kinetics of the furnace (or acid extrudes) or air conditioner (or acid loaders). Finally, just as a temperature-control system might benefit from environmental sensors that provide clues about cold and heat loading, at least some cells seem to have extracellular CO(2) or extracellular HCO(3)(-) sensors that modulate acid-base transport.
大多数动物细胞用于调节细胞内pH值（pH(i)）的方法，在概念上与一个复杂系统调节房屋温度的方式并没有太大不同。正如房屋的热容量（C）可使因急性冷热负荷引起的温度（T）突然变化最小化一样，细胞的缓冲能力（β）可使因急性酸碱负荷引起的pH(i)突然变化最小化。然而，增加C（或β）只能使T（或pH(i)）的变化最小化；它并不能消除这些变化、使T（或pH(i)）恢复正常，或改变稳态T（或pH(i)）。房屋可能有一个炉子来升高T，而细胞通常有不止一种酸排出转运体（其输出酸和/或输入碱）来升高pH(i)。正如空调降低T一样，细胞通常有不止一种酸加载转运体来降低pH(i)。就像房屋可能通过产生分级增加的热量（或冷量）输出，来响应T的分级降低（或增加）一样，细胞通过分级增加（或降低）酸排出（或酸加载）速率，来响应pH(i)的分级降低（或增加）。稳态T（或pH(i)）只能因慢性冷（或酸）负荷或慢性热（或碱）负荷的变化而改变，例如由环境T（或pH）的变化、炉子（或酸排出体）或空调（或酸加载体）的动力学变化所导致。最后，就像温度控制系统可能受益于提供冷热负荷线索的环境传感器一样，至少一些细胞似乎有可调节酸碱转运的细胞外二氧化碳或细胞外碳酸氢根传感器。
