Koga Y, Sodeyama N, Satoh S, Teshigawara T, Yanagisawa T, Taira N, Endoh M
Department of Anesthesiology, Tohoku University School of Medicine, Sendai, Japan.
Jpn J Pharmacol. 1989 Aug;50(4):387-96. doi: 10.1254/jjp.50.387.
We examined K+-induced relaxation instead of contraction in the presence of Ca-antagonists by measuring isometric tension in the tracheal smooth muscle isolated from guinea pigs. Cumulative administration of KCl (10-90 mM) induced a concentration-dependent contraction. When the muscle was pretreated with low concentrations of Ca-antagonists, cumulative administration of KCl caused a mild contraction, followed by a moderate relaxation. In the muscle pretreated with high concentrations of Ca-antagonists, KCl revealed a concentration-related relaxation without contraction. The potency ratios of Ca-antagonists to reverse the KCl-induced contraction to relaxation were nifedipine : verapamil : diltiazem = 94:4:1. This order of potency was quite similar to that of Ca-antagonists to relax the muscle precontracted with KCl (30 mM). Magnitudes of KCl (30 m,)-induced relaxation in the presence of Ca-antagonists were similar to those caused by Ca-antagonists in the KCl (30 mM)-precontracted muscles. Thus, K+-induced relaxation in the airway smooth muscle in the presence of Ca-antagonists may be due to the voltage-dependent increase in binding of Ca-antagonists to calcium channels.
我们通过测量从豚鼠分离的气管平滑肌的等长张力，研究了在存在钙拮抗剂的情况下钾离子诱导的舒张而非收缩。累积给予氯化钾（10 - 90 mM）可诱导浓度依赖性收缩。当肌肉用低浓度钙拮抗剂预处理时，累积给予氯化钾会引起轻度收缩，随后是中度舒张。在用高浓度钙拮抗剂预处理的肌肉中，氯化钾显示出与浓度相关的舒张且无收缩。钙拮抗剂将氯化钾诱导的收缩转变为舒张的效价比为硝苯地平：维拉帕米：地尔硫卓 = 94:4:1。这种效价顺序与钙拮抗剂使预先用氯化钾（30 mM）收缩的肌肉舒张的效价顺序非常相似。在存在钙拮抗剂的情况下，氯化钾（30 mM）诱导的舒张幅度与在预先用氯化钾（30 mM）收缩的肌肉中钙拮抗剂引起的舒张幅度相似。因此，在存在钙拮抗剂的情况下气道平滑肌中钾离子诱导的舒张可能是由于钙拮抗剂与钙通道结合的电压依赖性增加所致。
