Taniguchi J, Furukawa K I, Shigekawa M
Department of Molecular Physiology, National Cardiovascular Center Research Institute, Osaka, Japan.
Pflugers Arch. 1993 May;423(3-4):167-72. doi: 10.1007/BF00374390.
By using a patch clamp technique, we examined the effect of cyclic guanosine monophosphate (cGMP)-dependent protein kinase (G kinase) on Ca(2+)-activated maxi K+ channels in canine coronary artery smooth muscle cells. Maxi K+ channels (274 +/- 4 pS in symmetrical 140 mM KCl at 24-26 degrees C) were activated by cytoplasmic Ca2+ and were completely blocked by 100 nM charybdotoxin (CTX). G kinase (300 U/ml) added to the cytoplasmic face of the membrane patch shifted the voltage dependence of these channels by about 25 mV in the negative direction in the presence of 1 microM Ca2+, 50 microM cGMP and 1 mM magnesium adenosine triphosphate. At -50 mV and 1 microM Ca2+, G kinase treatment increased the mean number of open channels 4.5-fold compared with the control. alpha-Human atrial natriuretic peptide (ANP, 100 nM) reduced the isometric tension of coronary arterial rings elicited by 14 or 24 mM KCl, but failed to relax the artery contracted by 34 mM KCl. Addition of 100 nM CTX augmented tension development elicited by 24 mM KCl and totally prevented ANP from relaxing the arterial rings. These results indicate that G kinase-dependent protein phosphorylation activates maxi K+ channels in canine coronary smooth muscle, and further suggest that the G kinase-induced activation of maxi K+ channels may cause hyperpolarization and relaxation of coronary artery.
通过使用膜片钳技术，我们研究了环磷酸鸟苷（cGMP）依赖性蛋白激酶（G激酶）对犬冠状动脉平滑肌细胞中Ca(2+)激活的大电导钾通道的影响。大电导钾通道（在24 - 26℃、对称的140 mM KCl中为274 +/- 4 pS）由细胞质Ca2+激活，并被100 nM iberiotoxin（CTX）完全阻断。在存在1 microM Ca2+、50 microM cGMP和1 mM三磷酸镁腺苷的情况下，将G激酶（300 U/ml）添加到膜片的细胞质面，使这些通道的电压依赖性向负方向移动约25 mV。在-50 mV和1 microM Ca2+条件下，与对照相比，G激酶处理使开放通道的平均数量增加了4.5倍。α-人心房利钠肽（ANP，100 nM）降低了由14或24 mM KCl引起的冠状动脉环的等长张力，但未能使由34 mM KCl收缩的动脉舒张。添加100 nM CTX增强了由24 mM KCl引起的张力发展，并完全阻止了ANP使动脉环舒张。这些结果表明，G激酶依赖性蛋白磷酸化激活了犬冠状动脉平滑肌中的大电导钾通道，并进一步表明G激酶诱导的大电导钾通道激活可能导致冠状动脉超极化和舒张。
