Shimano M, Nakaya Y, Fukui R, Kamada M, Hamada Y, Maeda K, Aono T
Department of Obstetrics and Gynecology, Tokushima University, Tokushima, Japan.
Gynecol Obstet Invest. 2000;49(4):249-54. doi: 10.1159/000010254.
To investigate the mechanism of human uterine smooth muscle relaxation, the activation of Ca2+-activated K+ channels in cultured myometrial cells obtained from human pregnant myometrium at term by nitric oxide was evaluated at the single cell level using the patch-clamp technique. The open probability of the K+ channel after the addition of 3 x 10(-3) M isosorbide dinitrate, a nitric oxide donor (0.116 +/- 0.048) was significantly higher than that before the addition (0.059 +/- 0.032; n = 9, p < 0.01). In myometrial cells pretreated with lipopolysaccharide, activation of K+ channels was also noted after the addition of L-arginine (10(-4) M; open probability increased from 0.179 +/- 0.076 to 0.380 +/- 0.105, n = 9, p < 0.01: 10(-3) M; open probability increased from 0.073 +/- 0.050 to 0.242 +/- 0.098, n = 12, p < 0.01). Either 10(-3) M N-nitro-L-arginine-methyl-ester, an inhibitor of nitric oxide synthase, or 10(-6) M methylene blue, an inhibitor of guanylate cyclase, abolished activation of the K+ channel by 10(-3) M L-arginine in pretreated myometrial cells with lipopolysaccharide. Application of 10(-3) M L-arginine to the intracellular surface of an excised inside-out patch in the myometrial cells pretreated with lipopolysaccharide failed to increase Ca2+-activated K+ channel activity, suggesting that the activation was mediated by intracellular messengers. These results indicate that nitric oxide should control human myometrial relaxation during pregnancy via activation of Ca2+-activated K+ channels.
为研究人子宫平滑肌舒张的机制，采用膜片钳技术在单细胞水平评估了一氧化氮对足月妊娠人子宫肌层培养的肌层细胞中钙激活钾通道的激活作用。添加3×10⁻³ M硝酸异山梨酯（一种一氧化氮供体）后，钾通道的开放概率（0.116±0.048）显著高于添加前（0.059±0.032；n = 9，p<0.01）。在用脂多糖预处理的肌层细胞中，添加L-精氨酸（10⁻⁴ M；开放概率从0.179±0.076增加到0.380±0.105，n = 9，p<0.01；10⁻³ M；开放概率从0.073±0.050增加到0.242±0.098，n = 12，p<0.01）后也观察到钾通道的激活。一氧化氮合酶抑制剂10⁻³ M N-硝基-L-精氨酸甲酯或鸟苷酸环化酶抑制剂10⁻⁶ M亚甲蓝均可消除脂多糖预处理的肌层细胞中10⁻³ M L-精氨酸对钾通道的激活作用。将10⁻³ M L-精氨酸应用于脂多糖预处理的肌层细胞中切除的内面向外膜片的细胞内表面，未能增加钙激活钾通道活性，表明该激活是由细胞内信使介导的。这些结果表明，一氧化氮应通过激活钙激活钾通道来控制妊娠期间人子宫肌层的舒张。
