Suzuki K, Koyama I
Department of Bio-Medical Engineering, School of High-Technology for Human Welfare, Tokai University, Numazu, Japan.
Jpn J Physiol. 1996 Feb;46(1):43-52. doi: 10.2170/jjphysiol.46.43.
The effects of cyclic AMP-dependent protein kinase (PKA) on non-selective cation (NSC) channels in the plasma membrane of guinea-pig and mouse pancreatic acinar cells were studied by patch-clamp single-channel techniques. In both species, ATP (1.4 mM) acting on the inside of the membrane (Ca2+ concentration, 10(-6)M) inhibited the opening of the NSC channel with a unit conductance of 25 pS. The addition of a catalytic unit of PKA (25 U/ml) in the presence of ATP to the inside of guinea-pig cells evoked an opening of a new channel, which is a Ca(2+)-activated and voltage-sensitive NSC channel with a unit conductance of about 45 pS (in symmetrical monovaleńt cation-rich solution). On the other hand, 25 pS Ca(2+)-activated NSC channel in mouse cells was re-opened by identical PKA application. The application of PKA-inhibitor did not activate NSC channels in either species. The addition of 10(-6)M ACh to the bath solution containing 10(-6)M insulin, whose addition with ACh has been reported to increase cAMP, evoked a marked and sustained increase in the opening of the guinea-pig 45 pS or the mouse 25 pS NSC channel in intact cells (cell-attached configurations). This was not seen in the absence of insulin. These results suggest that the cAMP-dependent mechanism in the pancreatic acinar cells can activate NSC channels in the presence of ATP on the inside of the cell.
采用膜片钳单通道技术，研究了环磷酸腺苷（cAMP）依赖性蛋白激酶（PKA）对豚鼠和小鼠胰腺腺泡细胞质膜上非选择性阳离子（NSC）通道的影响。在这两个物种中，作用于膜内侧的ATP（1.4 mM，钙离子浓度为10⁻⁶M）可抑制单位电导为25 pS的NSC通道开放。在ATP存在的情况下，向豚鼠细胞内侧加入PKA催化亚基（25 U/ml），可诱发一个新通道开放，该通道是一种钙离子激活且电压敏感的NSC通道，单位电导约为45 pS（在富含单价阳离子的对称溶液中）。另一方面，通过相同的PKA作用可使小鼠细胞中25 pS的钙离子激活NSC通道重新开放。PKA抑制剂的应用在这两个物种中均未激活NSC通道。向含有10⁻⁶M胰岛素的浴液中加入10⁻⁶M乙酰胆碱（ACh），据报道ACh与胰岛素一起添加可增加cAMP，这可使完整细胞（细胞贴附模式）中豚鼠45 pS或小鼠25 pS的NSC通道开放显著且持续增加。在没有胰岛素的情况下则未观察到这种现象。这些结果表明，胰腺腺泡细胞中cAMP依赖性机制在细胞内侧存在ATP的情况下可激活NSC通道。
