Yamamoto Shintaro, Ishihara Keiko, Ehara Tsuguhisa, Shioya Takao
Department of Physiology, Saga Medical School, Saga, 849-8501 Japan.
Jpn J Physiol. 2004 Feb;54(1):31-8. doi: 10.2170/jjphysiol.54.31.
The cell-volume regulation by swelling-activated Cl- current (I(Cl,swell)) was studied in guinea pig ventricular myocytes, using a microscopic video-image analysis. We have previously shown that in ventricular cells depolarized in high-K+ ([K+]o>45 mM) solution, an activation of the cyclic AMP-dependent Cl- current (I(Cl,cAMP)) leads to cell swelling. We first investigated the mechanism underlying the I(Cl,cAMP)-independent recovery (shrinkage) of the swollen cells. They shrank when the membrane potential (Vm) was made negative to the equilibrium potential of Cl- (ECl) by lowering [K+]o or [Cl-]o in the high-K+ solution. This shrinkage was attenuated by the inhibitors (DIDS, glibenclamide, furosemide) of swelling-activated Cl- current (I(Cl,swell)). These findings suggested an involvement of I(Cl,swell) in the observed isosmotic cell shrinkage. On the other hand, an application of hyposmotic (70% of control) solution to the cells at normal [K+]o (ECl>Vm) induced a cell swelling, and the swollen cells underwent a slight but definite spontaneous cell shrinkage during hyposmotic challenge, indicating the operation of the mechanism of regulatory volume decrease (RVD). This RVD was pronounced at low [Cl-]o, at which ECl was much more positive than Vm. On the contrary, when the hyposmotic solution was applied to the cells at high [K+]o, at which ECl was negative to Vm, the cells swelled vigorously and monotonically without showing RVD, the swelling being much greater than that seen at normal [K+]o. Both the RVD at normal [K+]o and the extra cell swelling at high [K+]o were suppressed by DIDS. These results suggest that I(Cl,swell) activated by cell swelling can shrink or inflate the cardiac cells under hyposmotic as well as isosmotic conditions, depending on Vm and ECl.
采用显微视频图像分析技术，在豚鼠心室肌细胞中研究了肿胀激活的氯离子电流（I(Cl,swell)）对细胞体积的调节作用。我们先前已经表明，在高钾（[K+]o>45 mM）溶液中去极化的心室细胞中，环磷酸腺苷依赖性氯离子电流（I(Cl,cAMP)）的激活会导致细胞肿胀。我们首先研究了肿胀细胞不依赖I(Cl,cAMP)的恢复（收缩）机制。当通过降低高钾溶液中的[K+]o或[Cl-]o使膜电位（Vm）负于氯离子平衡电位（ECl）时，细胞会收缩。这种收缩被肿胀激活的氯离子电流（I(Cl,swell)）的抑制剂（二异硫氰酸二苯乙烯酯、格列本脲、呋塞米）减弱。这些发现表明I(Cl,swell)参与了观察到的等渗细胞收缩。另一方面，在正常[K+]o（ECl>Vm）下向细胞施加低渗（对照的70%）溶液会导致细胞肿胀，并且在低渗刺激期间肿胀的细胞会经历轻微但确定的自发细胞收缩，这表明存在调节性容积减小（RVD）机制。在低[Cl-]o时，ECl比Vm更正，这种RVD很明显。相反，当在高[K+]o下向细胞施加低渗溶液时，此时ECl负于Vm，细胞会剧烈且单调地肿胀，不显示RVD，肿胀程度远大于在正常[K+]o时所见。正常[K+]o时的RVD和高[K+]o时额外的细胞肿胀均被二异硫氰酸二苯乙烯酯抑制。这些结果表明，细胞肿胀激活的I(Cl,swell)可根据Vm和ECl在低渗以及等渗条件下使心脏细胞收缩或膨胀。
