Etiology of the membrane potential of rat white fat adipocytes
Etiology of the membrane potential of rat white fat adipocytes
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DOI：
10.1152/ajpendo.00446.2013
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发表时间：
2014-07-15
影响因子：
5.1
通讯作者：
Smith, Paul A.
中科院分区：
文献类型：
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作者：
Bentley, Donna C.;Pulbutr, Pawitra;Smith, Paul A.
质膜电位(Vm)是许多生理过程的关键，然而，其在白色脂肪脂肪细胞中的离子病因尚不清楚。为了解决这个问题，我们在分离的原代白色脂肪细胞及其细胞模型3T3-L1中采用了穿孔膜片电流钳和细胞附着式膜片钳方法。原代和3T3-L1脂肪细胞的静息Vm分别为-32.1+/-1.2 mV(n=95)和-28.8+/-1.2 mV(n=87)。Vm与细胞大小和脂肪含量无关。等摩尔取代Na+使细胞外K+升高至50 mM时，对Vm无影响，而用膜阳离子N-甲基-D-葡萄糖胺(+)取代细胞外K+使Vm超极化16 mV，表明非选择性阳离子通透性。胞外133 mM的氯离子被葡萄糖酸去极化25 mV，而氯离子被i-取代则引起-9 mV的超极化。异丙肾上腺素(10mU M)对Vm有显著去极化作用，而胰岛素(100 NM)对Vm无明显去极化作用。单通道离子的活度不受电压的影响，电流指示氯离子的内向斜率电导为16+/-1.3ps(n=11)，反转电位接近氯-平衡电位-29+/-1.6 mV。虽然细胞外Cl-的减少使脂肪细胞内的Ca(2+)浓度升高，但其幅度不如细胞外K+升高所产生的幅度大。综上所述，白色脂肪细胞的Vm符合Goldman-Hodgkin-Katz方程，其对Cl-的通透性占主导地位，其生物物理和单通道特性表明其具有体积敏感的阴离子通道特性。因此，血清氯稳态的改变或脂肪细胞通过药物对该阴离子的通透性将影响其Vm、细胞内钙离子，最终影响其功能及其在代谢控制中的作用。
The plasma membrane potential (Vm) is key to many physiological processes; however, its ionic etiology in white fat adipocytes is poorly characterized. To address this question, we employed the perforated patch current clamp and cell-attached patch clamp methods in isolated primary white fat adipocytes and their cellular model 3T3-L1. The resting Vm of primary and 3T3-L1 adipocytes were -32.1 +/- 1.2 mV (n = 95) and -28.8 +/- 1.2 mV (n = 87), respectively. Vm was independent of cell size and fat content. Elevation of extracellular K+ to 50 mM by equimolar substitution of bath Na+ did not affect Vm, whereas substitution of bath Na+ with the membrane-impermeant cation N- methyl-D-glucamine(+) -hyperpolarized Vm by 16 mV, data indicative of a nonselective cation permeability. Substitution of 133 mM extracellular Cl- with gluconate-depolarized Vmby 25 mV, whereas Cl- substitution with I- caused a -9 mV hyperpolarization. Isoprenaline (10 mu M), but not insulin (100 nM), significantly depolarized Vm. Single-channel ion activity was voltage independent; currents were indicative for Cl- with an inward slope conductance of 16 +/- 1.3 pS (n = 11) and a reversal potential close to the Cl- equilibrium potential, -29 +/- 1.6 mV. Although the reduction of extracellular Cl- elevated the intracellular Ca(2+)of adipocytes, this was not as large as produced by elevation of extracellular K+. In conclusion, the Vm of white fat adipocytes is well described by the Goldman-Hodgkin-Katz equation with a predominant permeability to Cl-, where its biophysical and single-channel properties suggest a volume-sensitive anion channel identity. Consequently, changes in serum Cl- homeostasis or the adipocyte's permeability to this anion via drugs will affect its Vm, intracellular Ca2+, and ultimately its function and its role in metabolic control.