Osmotic gradient-induced water permeation across the sarcolemma of rabbit ventricular myocytes.
Osmotic gradient-induced water permeation across the sarcolemma of rabbit ventricular myocytes.
复制标题
DOI：
10.1085/jgp.107.4.503
复制
发表时间：
1996-04
期刊：
影响因子：
--
通讯作者：
Baumgarten CM
中科院分区：
文献类型：
--
作者：
Suleymanian MA;Baumgarten CM
通过观察兔心室肌细胞渗透性膨胀和收缩的动力学和温度依赖性，探讨了水渗透穿过肌膜的机制。膨胀的幅度以及膨胀和收缩的动力学是温度依赖性的，但收缩的幅度在6 ℃、22 ℃和37 ℃下非常相似。膜水力传导率Lp在22 ℃时约为1.2 × 10（-10）升·N-1.s-1，对应于渗透系数Pf为16 μ m·s-1，并且与水通量的方向、施加的渗透梯度的大小（35-165 mosm/升）和初始细胞体积无关。该Lp值代表上限，因为膜被假定为光滑表面。基于电容膜面积，Lp为0.7至0.9 × 10（-10）升·N-1.s-1。然而，心室中Lp的估计值比人红细胞中的低15至25倍，并且在无蛋白质脂质双层和无功能性水通道（水通道蛋白）的生物膜报告的值范围内。未搅拌层的效果评价表明，在最坏的情况下，它们使Lp降低≤ 2.3%。对Lp的温度依赖性的分析表明，其表观阿氏活化能Ea '在6 ℃和22 ℃之间为11.7 +/- 0.9 kcal/mol，在22 ℃和37 ℃之间为9.2 +/- 0.9 kcal/mol。这些值明显大于通常发现的通过水填充孔的水流的值，约为4千卡/摩尔，并且在没有功能性水通道的人造和天然膜的范围内。总之，这些数据有力地证明，心室肌细胞中绝大多数渗透水通量穿透脂质双层本身，而不是通过充满水的孔。
The mechanism of water permeation across the sarcolemma was characterized by examining the kinetics and temperature dependence of osmotic swelling and shrinkage of rabbit ventricular myocytes. The magnitude of swelling and the kinetics of swelling and shrinkage were temperature dependent, but the magnitude of shrinkage was very similar at 6 degrees, 22 degrees, and 37 degrees C. Membrane hydraulic conductivity, Lp, was approximately 1.2 x 10(-10) liter.N-1.s-1 at 22 degrees C, corresponding to an osmotic permeability coefficient, Pf, of 16 microns.s-1, and was independent of the direction of water flux, the magnitude of the imposed osmotic gradient (35-165 mosm/liter), and the initial cell volume. This value of Lp represents an upper limit because the membrane was assumed to be a smooth surface. Based on capacitive membrane area, Lp was 0.7 to 0.9 x 10(-10) liter.N-1.s-1. Nevertheless, estimates of Lp in ventricle are 15 to 25 times lower than those in human erythrocytes and are in the range of values reported for protein- free lipid bilayers and biological membranes without functioning water channels (aquaporin). Evaluation of the effect of unstirred layers showed that in the worst case they decrease Lp by < or = 2.3%. Analysis of the temperature dependence of Lp indicated that its apparent Arrhenius activation energy, Ea', was 11.7 +/- 0.9 kcal/mol between 6 degrees and 22 degrees C and 9.2 +/- 0.9 kcal/mol between 22 degrees and 37 degrees C. These values are significantly greater than that typically found for water flow through water-filled pores, approximately 4 kcal/mol, and are in the range reported for artificial and natural membranes without functioning water channels. Taken together, these data strongly argue that the vast majority of osmotic water flux in ventricular myocytes penetrates the lipid bilayer itself rather than passing through water-filled pores.