中华绒螯蟹眼柄端髓X器官神经分泌细胞钙激活钾通道研究

Studies on calcium-activated potassium channel expressed by the neurosecretory cells of medulla terminalia X-organ in the eyestalks of Eriocheir sinensis

采用膜片钳的内面向外式记录了中华绒螯蟹眼柄端髓X器官(MTXO)神经内分泌细胞钙激活钾通道活动。结果表明,在对称性高钾溶液中(200mmol.L-1),钙激活钾通道的单通道活动为快速开放的矩形方波,时程长短不一,通道电导为(213.4±11.2)pS。在-80^+80mV钳制电压下,通道电流幅度及开放概率呈现明显的电压依赖性;随浴液游离Ca2+浓度的增加,通道的开放概率和开放数目增加,表现出明显的钙敏感性。药物敏感试验结果显示,80mmol.L-1四乙胺(TEA)可完全阻断通道活动。表明中华绒螯蟹眼柄端髓X器官(MTXO)神经分泌细胞钙激活钾通道(BKCa)具有大电导、电压依赖性、Ca2+敏感性和四乙胺(TEA)敏感性等特征。

Inside-out patch clamp technique was used to study the properties of calcium-activated potassium channel（BKca） of neurosecretory cells dissociated from medulla terminalia X-organ （MTXO） of Chinese mitten crab Eriocheir sinensis. Calcium-activated potassium channel was observerd in symmertrical high potassium solutions （200 mmol. L^-1）, and the single channel showed rapid-open rectangle waves with different durations and had a conductance of （213.4 ± 11.2） pS. At a series of the membrane potentials （from - 80 to ＋ 80 mV）, the current amplitude and the open state probability of single channel presented obvious voltage-dependency. In addition, the open state probability of single channel also increased in proportion to Ca^2＋ concentration in the bath solution, indicating that the single channel was obviously sensitive to intracellular free Ca^2＋ concentration. Furthermore, drug sensitivity testing revealed that tetraethylammonium （TEA, 80 mmol·L^-1） could completely block the single channel. The experiments suggested that BKca channel of neurosecretory cells dissociated from MTXO of Chinese mitten＇crab Eriocheir sinensis is voltage-dependent with a large conductance and is sensitive to Ca^2＋ and TEA.