Tang Yu-Rong, Yang Wei-Wei, Wang Yun, Gong Yao-Yao, Jiang Liu-Qin, Lin Lin
Department of Gastroenterology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
Digestion. 2015;91(3):187-96. doi: 10.1159/000371544. Epub 2015 Mar 14.
This study aimed to determine the effects of small-conductance Ca(2+)-activated K(+) (SK) channels in colonic relaxation and the regulation of SK channels by estrogen.
The contractile activity of muscle strips from male rats was estimated, and drugs including vehicle (DMSO), 17β-estradiol (E2), or apamin (SK blocker) were added, respectively. In a further experiment, muscle strips were preincubated with apamin before exposure to E2. The levels of the SK2 and SK3 protein expression in the colonic smooth muscle cells (SMCs) were detected. SMCs were treated with ICI 182780 (estrogen receptor [ER] antagonist) plus E2, BSA-E2, PPT (ERα agonist), or DPN (ERβ agonist). SK3 mRNA and protein expression levels were detected.
The muscle strips responded to E2 with a decrease and to apamin with a transient increase in tension. Preincubation with apamin partially prevented E2-induced relaxation. Two SK channel subtypes, SK2 and SK3, were coexpressed with α-actin in colonic SMCs. The quantitative ratio of the SK transcriptional expression in colonic SMCs was SK3 > SK2. The SK3 expression was upregulated by E2, and was downregulated by ICI 182780, but was not influenced by BSA-E2. Furthermore, the effect of PPT on the expression of SK3 was almost the same as that of E2, while DPN did not influence the protein expression of SK3.
These findings indicate that SK3 is involved in the E2-induced relaxing effect on rat colonic smooth muscle. Furthermore, E2 upregulates the expression of SK3 in rat SMCs, and that this effect is mediated via the ERα receptor.
本研究旨在确定小电导钙激活钾（SK）通道在结肠舒张中的作用以及雌激素对SK通道的调节作用。
评估雄性大鼠肌肉条的收缩活性，并分别添加包括溶剂（二甲基亚砜）、17β-雌二醇（E2）或蜂毒明肽（SK阻滞剂）在内的药物。在进一步的实验中，在暴露于E2之前，将肌肉条与蜂毒明肽预孵育。检测结肠平滑肌细胞（SMC）中SK2和SK3蛋白表达水平。用ICI 182780（雌激素受体[ER]拮抗剂）加E2、牛血清白蛋白-E2、PPT（ERα激动剂）或DPN（ERβ激动剂）处理SMC。检测SK3 mRNA和蛋白表达水平。
肌肉条对E2的反应是张力降低，对蜂毒明肽的反应是张力短暂升高。用蜂毒明肽预孵育可部分阻止E2诱导的舒张。两种SK通道亚型SK2和SK3与α-肌动蛋白在结肠SMC中共表达。结肠SMC中SK转录表达的定量比例为SK3>SK2。SK3表达受E2上调，受ICI 182780下调，但不受牛血清白蛋白-E2影响。此外，PPT对SK3表达的影响与E2几乎相同，而DPN不影响SK3的蛋白表达。
这些发现表明SK3参与E2诱导的大鼠结肠平滑肌舒张作用。此外，E2上调大鼠SMC中SK3的表达，且该作用通过ERα受体介导。
