Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, USA.
J Neuroendocrinol. 2023 Jun;35(6):e13312. doi: 10.1111/jne.13312. Epub 2023 Jun 19.
Dilutional hyponatremia due to increased plasma arginine vasopressin (AVP) is associated with liver cirrhosis. However, plasma AVP remains elevated despite progressive hypoosmolality. This study investigated changes to inhibitory control of supraoptic nucleus (SON) AVP neurons during liver cirrhosis. Experiments were conducted with adult male Sprague-Dawley rats. Bile duct ligation was used as a model of chronic liver cirrhosis. An adeno-associated virus containing a construct with an AVP promoter and either green fluorescent protein (GFP) or a ratiometric chloride indicator, ClopHensorN, was bilaterally injected into the SON of rats. After 2 weeks, rats received either BDL or sham surgery, and liver cirrhosis was allowed to develop for 4 weeks. In vitro, loose patch recordings of action potentials were obtained from GFP-labeled and unlabeled SON neurons in response to a brief focal application of the GABA agonist muscimol (100 μM). Changes to intracellular chloride ([Cl]i) following muscimol application were determined by changes to the fluorescence ratio of ClopHensorN. The contribution of cation chloride cotransporters NKCC1 and KCC2 to changes in intracellular chloride was investigated using their respective antagonists, bumetanide (BU, 10 μM) and VU0240551 (10 μM). Plasma osmolality and hematocrit were measured as a marker of dilutional hyponatremia. The results showed reduced or absent GABA -mediated inhibition in a greater proportion of AVP neurons from BDL rats as compared to sham rats (100% inhibition in sham vs. 47% in BDL, p = .001). Muscimol application was associated with increased [Cl]i in most cells from BDL as compared to cells from sham rats (χ = 30.24, p < .001). NKCC1 contributed to the impaired inhibition observed in BDL rats (p < .001 BDL - BU vs. BDL + BU). The results show that impaired inhibition of SON AVP neurons and increased intracellular chloride contribute to the sustained dilutional hyponatremia in liver cirrhosis.
由于血浆精氨酸血管加压素（AVP）增加导致的稀释性低钠血症与肝硬化有关。然而，尽管渗透压逐渐降低，血浆 AVP 仍保持升高。本研究探讨了肝硬化过程中视上核（SON）AVP 神经元抑制性控制的变化。实验采用成年雄性 Sprague-Dawley 大鼠进行。胆管结扎被用作慢性肝硬化的模型。腺相关病毒（AAV）包含一个带有 AVP 启动子的构建体，该构建体与绿色荧光蛋白（GFP）或比率氯离子指示剂 ClopHensorN 融合，双侧注射到大鼠的 SON 中。2 周后，大鼠接受 BDL 或假手术，允许肝硬化发展 4 周。在体外，通过短暂聚焦应用 GABA 激动剂 muscimol（100 μM），从 GFP 标记和未标记的 SON 神经元中获得动作电位的松散贴片记录。通过 ClopHensorN 的荧光比值变化来确定 muscimol 应用后细胞内氯离子 ([Cl]i) 的变化。使用其各自的拮抗剂布美他尼（BU，10 μM）和 VU0240551（10 μM）研究阳离子氯离子共转运蛋白 NKCC1 和 KCC2 对细胞内氯离子变化的贡献。测量血浆渗透压和红细胞压积作为稀释性低钠血症的标志物。结果显示，与 sham 组相比，BDL 组大鼠中 GABA 介导的抑制减少或缺失（sham 组 100%抑制，BDL 组 47%，p=0.001）。与 sham 组相比，BDL 组的大多数细胞中 muscimol 的应用与细胞内氯离子增加有关（χ2=30.24，p<0.001）。NKCC1 对 BDL 大鼠观察到的抑制受损有贡献（p<0.001 BDL-BU 与 BDL+BU）。结果表明，SON AVP 神经元抑制受损和细胞内氯离子增加导致肝硬化中持续的稀释性低钠血症。
