Wayne R, Tazawa M
Department of Botany, Faculty of Science, University of Tokyo, Japan.
J Membr Biol. 1990 Jun;116(1):31-9. doi: 10.1007/BF01871669.
The hydraulic resistance was measured on internodal cells of Nitellopsis obtusa using the method of transcellular osmosis. The hydraulic resistance was approximately 2.65 pm-1 sec Pa, which corresponds to an osmotic permeability of 101.75 microns sec-1 (at 20 degrees C). p-Chloromercuriphenyl sulfonic acid (pCMPS) (0.1-1 mM, 60 min) reversibly increases the hydraulic resistance in a concentration-dependent manner. pCMPS does not have any effect on the cellular osmotic pressure. pCMPS increases the activation energy of water movement from 16.84 to 32.64 kJ mol-1, indicating that it inhibits water movement by modifying a low resistance pathway. pCMPS specifically increases the hydraulic resistance to exosmosis, but does not influence endosmosis. By contrast, nonyltriethylammonium (C9), a blocking agent of K+ channels, increases the hydraulic resistance to endosmosis, but does not affect that to exosmosis. These data support the hypothesis that water moves through membrane proteins in characean internodal cells and further that the polarity of water movement may be a consequence of the differential gating of membrane proteins on the endo- and exoosmotic ends.
采用跨细胞渗透法测定了钝节拟丽藻节间细胞的水力阻力。水力阻力约为2.65 pm⁻¹ s Pa，这对应于101.75微米 s⁻¹的渗透渗透率（在20摄氏度时）。对氯汞苯磺酸（pCMPS）（0.1 - 1 mM，60分钟）以浓度依赖的方式可逆地增加水力阻力。pCMPS对细胞渗透压没有任何影响。pCMPS将水移动的活化能从16.84 kJ mol⁻¹增加到32.64 kJ mol⁻¹，表明它通过改变低阻力途径来抑制水的移动。pCMPS特异性地增加对外渗的水力阻力，但不影响内渗。相比之下，K⁺通道阻滞剂壬基三乙铵（C9）增加对内渗的水力阻力，但不影响对外渗的水力阻力。这些数据支持了这样的假设，即水通过轮藻节间细胞中的膜蛋白移动，并且进一步表明水移动的极性可能是内渗和外渗末端膜蛋白不同门控的结果。
