Hepatocyte water volume and potassium activity during hypotonic stress.
Hepatocyte water volume and potassium activity during hypotonic stress.
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低渗应激期间的肝细胞水量和钾活性。
DOI：
10.1007/bf00231439
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Wondergem,R
中科院分区：
文献类型：
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作者：
Wang,K;Wondergem,R
肝细胞在低渗休克期间表现出调节性容积减少（RVD），包括细胞内K+和Cl−的损失，伴随着由于膜K+电导（GK）增加引起的跨膜电位（Vm）超极化。为了研究RVD过程中肝细胞K+的稳态，采用双管K+选择性微电极测量低渗应激过程中稳态细胞内K+活性（阿基）和Vm的变化。通过测量细胞内四甲基铵（TMA+）的变化来评价细胞水体积变化。用改良Krebs生理盐水灌流肝片。通过将外部蔗糖浓度逐步降低50 mm来产生低渗透压（0.8×300 mosm）。当肝片暴露于低渗应激4-5 min时，Vm从-27 ± 1 mV超极化至-46 ± 1 mV，Ki从91 ± 4 mm降低14%至78 ± 4 mm，恢复等渗溶液后，Vm和Ki均恢复至对照水平。在成对的测量中，低渗胁迫诱导VmandaKi在对照和添加哇巴因（1 mm）条件下的类似变化，并且这些值在渗透胁迫后恢复到其对照水平。在另一个配对的测量中，低渗休克首先诱导Vmin增加18 mV，而在对照条件下，Ki降低15%。在用TMA+加载肝细胞后，同样的低渗休克诱导Vmin增加14-mV，TMAi减少14%。这说明细胞内水体积增加了17%，这与当Ki用作标记物时获得的细胞水体积变化相同。然而，低渗应激引起的VmandaKi的变化被Ba ~（2+）部分阻断。我们的结论是：（i）低渗休克时，肝细胞Vm增加，aKid降低;（ii）低渗休克时和休克后肝细胞Vm的变化与Na ~+-K ~+泵无关;（iii）低渗休克时aKid降低主要是由于肝细胞肿胀所致。
Hepatocytes exhibit a regulatory volume decrease (RVD) during hypotonic shock, which comprises loss of intracellular K+and Cl−accompanied by hyperpolarization of transmembrane potential (Vm) due to an increase in membrane K+conductance, (GK). To examine hepatocyte K+homeostasis during RVD, double-barrel, K+-selective microelectrodes were used to measure changes in steady-state intracellular K+activity (aKi) andVmduring hyposmotic stress. Cell water volume change was evaluated by measuring changes in intracellular tetramethylammonium (TMA+). Liver slices were superfused with modified Krebs physiological salt solution. Hyposmolality (0.8×300 mosm) was created by a 50 mmstep-decrease of external sucrose concentration. HepatocyteVmhyperpolarized by 19 mV from −27 ± 1 to −46 ± 1 mV andaKidecreased by 14% from 91 ± 4 to 78 ± 4 mmwhen slices were exposed to hyposmotic stress for 4–5 min. BothVmandaKireturned to control level after restoring isosmotic solution. In paired measurements, hypotonic stress induced similar changes inVmandaKiboth control and added ouabain (1 mm) conditions, and these values returned to their control level after the osmotic stress. In another paired measurement, hypotonic shock first induced an 18-mV increase inVmand a 15% decrease inaKiin control condition. After loading hepatocytes with TMA+, the same hypotonic shock induced a 14-mV increase inVmand a 14% decrease inaTMAi. This accounted for a 17% increase of intracellular water volume, which was identical to the cell water volume change obtained whenaKiwas used as the marker. Nonetheless, hyposmotic stress-induced changes inVmandaKiwere blocked partly by Ba2+(2 mm). We conclude that (i) hepatocyteVmincreases andaKidecreases during hypotonic shock; (ii) the changes in hepatocyteVmandaKiduring and after hypotonic shock are independent of the Na+-K+pump; (iii) the decrease inaKiduring hypotonic stress results principally from hepatocyte swelling.