NON-PASSIVE CHLORIDE DISTRIBUTION IN MAMMALIAN HEART-MUSCLE - MICROELECTRODE MEASUREMENT OF THE INTRACELLULAR CHLORIDE ACTIVITY
NON-PASSIVE CHLORIDE DISTRIBUTION IN MAMMALIAN HEART-MUSCLE - MICROELECTRODE MEASUREMENT OF THE INTRACELLULAR CHLORIDE ACTIVITY
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DOI：
10.1113/jphysiol.1979.sp012956
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发表时间：
1979-01-01
影响因子：
5.5
通讯作者：
VAUGHANJONES, RD
中科院分区：
文献类型：
--
作者：
VAUGHANJONES, RD
使用液体离子交换器Cl敏感微电极连续测量细胞内Cl活性，**GRAPHIC**。半衰期绵羊心脏浦肯野纤维的体外培养。**图**。高于被动分布的预期值。5毫米。在细胞外碳酸氢盐/二氧化碳缓冲系统的存在下，它高出3-4倍，并且非常稳定；ECl[氯化物平衡电位]约为。35 mV对Em（静息膜电位）正。在没有碳酸氢盐/CO2的情况下（缓冲体系为HEPES[4-（2-羟乙基）-1-哌嗪- n " -2-乙磺酸]/O2的情况下），这一数值是前者的两倍多，但并不总是那么稳定；EC1大约是。20 mV正对Em。实验设计，以评估可能发生的最大可能误差在测量。**图形**。表明这不会很大，ECl的估计精确到8毫伏以内。Cl沿浓度和电位梯度向下移动的能力通过证明损失来建立。**图**。在无cl溶液中，当Em在高k溶液中离极化为ECl时增加。在这两种情况下，变化都在100-160分钟内完成。**图形**。[Ca]o[细胞外浓度]从0到12 mM的变化，或在低[Ca]o或零[Ca]o时有时发生的高达60 mV的Em去极化，对无cl溶液（葡萄糖醛酸盐取代）没有显著影响。只有2-3毫米。**图形**。[细胞外Cl活性]mM足以实质性地阻碍。**图**。在hepes缓冲溶液中。在高钾溶液（45 mM）中，Cl表现为被动分布，因为在平衡状态下，Em和ECl的差异小于2 mV。在hepes缓冲的Tyrode中，豚鼠静止乳头肌的ECl对Em平均为39 mV阳性。液体离子交换器Cl敏感微电极适用于研究绵羊浦肯野纤维和其他心脏组织的Cl调节。静息的测量。**图形**。在使用HEPES或碳酸氢盐缓冲的Tyrode时是准确的。讨论了这些结果与各种条件下膜Cl的表观渗透性的估计和可能存在的内向Cl泵的关系。
Liquid ion-exchanger Cl--sensitive micro-electrodes were used to make continuous measurements of the intracellular Cl activity, .**GRAPHIC**. of quiscent sheep cardiac Purkinje fibers in vitro. .**GRAPHIC**. was higher than that expected from a passive distribution, which would have been .apprx. 5 mM. It was 3-4 times higher in the presence of an extracellular bicarbonate/CO2 buffer-system and was very stable; ECl [chloride equilibrium potential] was .apprx. 35 mV positive to Em [resting membrane potential]. It was over twice as high in the nominal absence of bicarbonate/CO2 (when the buffer-system was HEPES[4-(2-hydroxyethyl)-1-piperazine-N''-2-ethanesulfonic acid]/O2) but was not always so stable; EC1 was about .apprx. 20 mV positive to Em. Experiments designed to assess the maximum possible error likely to occur in the measurement of .**GRAPHIC**. showed that this could not be large and that the estimates of ECl were accurate to within 8 mV. The ability of Cl to move down concentration and potential gradients was established by demonstrating a loss of .**GRAPHIC**. in Cl-free solutions and a gain when Em was depolarized positive to ECl in high-K solutions. In both cases the changes were complete within 100-160 min. The decline of .**GRAPHIC**. in Cl-free solutions (glucuronate-substituted) was not significantly affected by changes of [Ca]o [extracellular concentration] from 0 to 12 mM or by the depolarizations of Em of up to 60 mV that sometimes occurred in low or zero [Ca]o. Only 2-3 mM .**GRAPHIC**. [extracellular Cl activity] mM was sufficient to impede substantially the ready loss of .**GRAPHIC**. in HEPES-buffered solutions. In high-K solutions (45 mM), Cl appeared to be passively distributed since, at equilibrium, Em and ECl differed by less than 2 mV. In HEPES-buffered Tyrode ECl of quiescent papillary muscle of the guinea pig was an average 39 mV positive to Em. Liquid ion-exchanger Cl--sensitive micro-electrodes are suitable for studying the Cl regulation of sheep Purkinje fibers and probably of other cardiac tissues. The measurements of resting .**GRAPHIC**. are accurate when using HEPES or bicarbonate-buffered Tyrode. The results are discussed in relation to estimates of the apparent membrane Cl permeability under various conditions and the possible existence of an inwardly directed Cl pump.