SPATIAL VARIATIONS IN MEMBRANE-PROPERTIES IN THE INTACT RAT LENS
SPATIAL VARIATIONS IN MEMBRANE-PROPERTIES IN THE INTACT RAT LENS
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DOI：
10.1016/s0006-3495(92)81624-7
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发表时间：
1992-08-01
影响因子：
3.4
通讯作者：
MATHIAS, RT
中科院分区：
文献类型：
--
作者：
BALDO, GJ;MATHIAS, RT
我们使用线性频域技术测量了完整大鼠晶状体不同位置和深度的阻抗。这些数据被用来获得基于透镜结构的新电学模型的最佳拟合解，从而使我们能够估计作为位置函数的表面细胞膜(G(S))、纤维细胞膜(g(M))和缝隙连接(G(J))的局域电导。结果发现，晶状体中g(M)较小且比较均匀(2.02±0.58mU/cm~2)，前表面上皮细胞G(S)=1.26±0.19ms/cm~2，后表面分化纤维细胞G(S)=0.46±0.04ms/cm~2。因此，G(S)以一种逐步的方式围绕赤道变化。纤维细胞之间的G(J)在半径80%以内的位置相当均匀(0.75 S/厘米~2)，而在外侧20%处，G(J)从两极(0.66 S/厘米~2)到赤道(5.95 S/厘米~2)变化平缓且对称。G(J)的这种变化模式与Robinson和Patterson(1983)报告的内向和外向电流模式相似。货币。眼科报告2：843-847)。因此，我们认为，功能缝隙连接的不均匀分布，而不是表面细胞电导或Na/K泵，可能是导致这些电流流动的原因。在接触高钙和酸化过程中，缝隙连接解偶联也被检测到。高钙(20 mM，带有钙离子载体A23187)产生适度(两倍)的不可逆解偶联以及膜电位的大而不可逆的下降。我们没有进一步追查这一点。用20%和100%CO2气泡的Tyrode‘s酸化，仅在晶状体半径的20%外部分别产生5倍和15倍的可逆解偶联。其余80%的晶状体缝隙连接似乎对酸化有抵抗力，没有解偶联。
We have used linear frequency domain techniques to measure impedance at various locations and depths in the intact rat lens. The data are used to obtain best-fit solutions to a new electrical model based on lens structure, allowing us to estimate localized conductances of surface cell membranes (G(s)), fiber cell membranes (g(m)), and gap junctions (G(j)) as functions of position. We find that g(m) is small and fairly uniform throughout the lens (2.02 +/- 0.58-mu-S/cm2); for the anterior surface epithelial cells G(s) = 1.26 +/- 0.19 mS/cm2; for the posterior surface differentiating fiber cells G(s) = 0.46 +/- 0.04 mS/cm2. Thus, G(s) varies about the equator in a stepwise fashion. G(j) between fiber cells at locations interior to 80% of the radius is fairly uniform (0.75 S/cm2); but in the outer 20% G(j) varies smoothly and symmetrically from both poles (0.66 S/cm2) to equator (5.95 S/cm2). This pattern of variation in G(j) is similar to the pattern of inward and outward currents reported by Robinson and Patterson (1983. Curr. Eye Res. 2:843-847). We therefore suggest that the nonuniform distribution of functional gap junctions, not the surface cell conductance or Na/K pumps, may be responsible for directing these current flows. Gap junctional uncoupling during exposure to elevated calcium and acidification was also examined. High calcium (20 mM, with the calcium ionophore A23187) produced modest (twofold) irreversible uncoupling along with large, irreversible decreases in membrane potential. We did not pursue this further. Acidification with 20 and 100% CO2-bubbled Tyrode's produced 5- and 15-fold reversible uncoupling, respectively, only in the outer 20% of the lens radius. The remaining inner 80% of the lens gap junctions seemed resistant to the acidification and did not uncouple.