Intracellular pH transients in squid giant axons caused by CO2, NH3, and metabolic inhibitors.
Intracellular pH transients in squid giant axons caused by CO2, NH3, and metabolic inhibitors.
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DOI：
10.1085/jgp.67.1.91
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发表时间：
1976-01
期刊：
影响因子：
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通讯作者：
De Weer P
中科院分区：
文献类型：
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作者：
Boron WF;De Weer P
用玻璃pH微电极测定了鱿鱼巨轴突细胞内的pH值。在23 ° C下，人造海水（ASW）（pH 7.6-7.8）中的静止pHi为7.32 +/- 0.02（如果针对液体接界电位校正，则为7.28）。在恒定的外部pH值下，轴突暴露于5%CO2引起pHi急剧下降，而随后去除气体引起pHi超过其初始值。如果暴露于CO2的时间延长，则注意到两个额外的影响：（a）在暴露期间，pHi的快速初始下降之后是缓慢上升，以及（B）在暴露之后，过冲被大大夸大。外部NH 4Cl的应用导致pHi急剧上升;恢复正常ASW导致pHi返回到低于其初始值的值。如果暴露于NH 4Cl的时间延长，则注意到两个额外的影响：（a）在暴露期间，pHi的快速初始上升之后是缓慢下降，以及（B）在暴露之后，下冲被大大夸大。暴露于几种弱酸性代谢抑制剂导致pH下降，其可逆性取决于暴露的时间长度。用100 mM K-ASW反转H+的电化学梯度对短期暴露于叠氮化物导致的pHi变化没有影响。一个数学模型解释了NH 4Cl引起的pHi变化的基础上的NH3和NH 4+的被动运动。CO2和HCO 3-的同时被动运动不能解释CO2实验的结果;这些数据需要假设一个主动质子挤出和/或封存机制。
The intracellular pH (pHi) of squid giant axons has been measured using glass pH microelectrodes. Resting pHi in artificial seawater (ASW) (pH 7.6-7.8) at 23 degrees C was 7.32 +/- 0.02 (7.28 if corrected for liquid junction potential). Exposure of the axon to 5% CO2 at constant external pH caused a sharp decrease in pHi, while the subsequent removal of the gas caused pHi to overshoot its initial value. If the exposure to CO2 was prolonged, two additional effects were noted: (a) during the exposure, the rapid initial fall in pHi was followed by a slow rise, and (b) after the exposure, the overshoot was greatly exaggerated. Application of external NH4Cl caused pHi to rise sharply; return to normal ASW caused pHi to return to a value below its initial one. If the exposure to NH4Cl was prolonged, two additional effects were noted: (a) during the exposure, the rapid initial rise in pHi was followed by a slow fall, and (b) after the exposure, the undershoot was greatly exaggerated. Exposure to several weak acid metabolic inhibitors caused a fall in pHi whose reversibility depended upon length of exposure. Inverting the electrochemical gradient for H+ with 100 mM K- ASW had no effect on pHi changes resulting from short-term exposure to azide. A mathematical model explains the pHi changes caused by NH4Cl on the basis of passive movements of both NH3 and NH4+. The simultaneous passive movements of CO2 and HCO3-cannot explain the results of the CO2 experiments; these data require the postulation of an active proton extrusion and/or sequestration mechanism.