Chan H C, Fu W O, Chung Y W, Chan P S, Wong P Y
Department of Physiology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, N.T.
Biol Reprod. 1995 Mar;52(3):645-52. doi: 10.1095/biolreprod52.3.645.
An outwardly rectifying conductance was observed in primary cultured human epididymal cells under the patch-clamp whole-cell configuration in KCl pipette and bath solutions. Removal of Cl- from intracellular and extracellular solutions did not affect this conductance, but substitution of K+ with N-methyl-D-glucamine in both solutions completely blocked the current. The current magnitude was also found to be affected by intracellular but not extracellular K+ concentrations. The conductance could be inhibited by the cation channel blockers, barium and tetraethylammonium chloride. Single-channel recordings from the same cell population also revealed the presence of a conductance of about 150 pS with voltage dependence and blocker sensitivity similar to those observed for the whole-cell current. This cation conductance was not affected by changes in solution osmolarity but could be activated by extracellular ATP. ATP activation of the conductance could be mimicked by ionomycin and inhibited by BAPTA-AM, an agent that suppresses intracellular free Ca2+. This ATP-regulated cation conductance may be responsible for secreting K+ across the epididymal epithelium, resulting in an observed K+ concentration much higher in the lumen of the epididymis than in the blood.
在膜片钳全细胞模式下，于含氯化钾的移液器和浴槽溶液中对原代培养的人附睾细胞进行观察时，发现了一种外向整流电导。从细胞内和细胞外溶液中去除氯离子并不影响这种电导，但在两种溶液中用N-甲基-D-葡萄糖胺替代钾离子则完全阻断了电流。还发现电流幅度受细胞内钾离子浓度而非细胞外钾离子浓度的影响。该电导可被阳离子通道阻滞剂钡离子和氯化四乙铵抑制。对同一细胞群体进行的单通道记录也显示存在一种约150 pS的电导，其电压依赖性和阻滞剂敏感性与全细胞电流所观察到的相似。这种阳离子电导不受溶液渗透压变化的影响，但可被细胞外ATP激活。离子霉素可模拟ATP对该电导的激活作用，而抑制细胞内游离钙离子的试剂BAPTA-AM则可抑制这种激活。这种ATP调节的阳离子电导可能负责跨附睾上皮分泌钾离子，从而导致附睾管腔中的钾离子浓度远高于血液中的钾离子浓度。
