Fan S F, Wang S, Kao C Y
Department of Physiology and Biophysics, State University of New York at Stony Brook 11794.
Biochem Biophys Res Commun. 1994 May 30;201(1):24-9. doi: 10.1006/bbrc.1994.1664.
The outward K+ current induced by step depolarization of freshly dispersed myocytes of guinea-pig taenia coli decreased about 80% upon treatment with 3 mM tetraethylammonium chloride (TEA). Isoproterenol (ISO, 2-5 microM) restored it to a large extent. This restoration did not occur in the presence of propranolol (2 microM). In single-channel recordings from cell-attached patches, the activity of maxi-K+ channel is dominant. When 3 mM TEA is incorporated in the pipette solution, the dominant channel-openings observed had much smaller unitary conductance. On the addition of ISO (2 microM) to the bath solution, but not to the pipette solution, K(+)-channel openings with unitary conductance similar to that without TEA treatment appeared. Cyclic AMP incorporated into the cytoplasm through the pipette was ineffective. These results indicate that ISO release TEA decrease of maxi-K+ channel conductance through some intracellular second messenger system other than adenylyl cyclase-protein kinase A system.
豚鼠结肠带新鲜分散的肌细胞经阶跃去极化诱导的外向钾电流在用3 mM四乙铵（TEA）处理后降低约80%。异丙肾上腺素（ISO，2 - 5 μM）在很大程度上使其恢复。在普萘洛尔（2 μM）存在的情况下，这种恢复未发生。在细胞贴附片的单通道记录中，大电导钾通道的活性占主导。当移液管溶液中加入3 mM TEA时，观察到的主要通道开放具有小得多的单位电导。向浴液而非移液管溶液中加入ISO（2 μM）时，出现了单位电导与未用TEA处理时相似的钾通道开放。通过移液管导入细胞质的环磷酸腺苷无效。这些结果表明，ISO通过腺苷酸环化酶 - 蛋白激酶A系统以外的一些细胞内第二信使系统释放TEA降低大电导钾通道电导。
