Shahi Pawan Kumar, Choi Seok, Jeong Yu Jin, Park Chan Guk, So Insuk, Jun Jae Yeoul
Department of Physiology, College of Medicine, Chosun University, 309 Pilmun-daero, Dongku, Gwangju, 501-375, Korea.
Naunyn Schmiedebergs Arch Pharmacol. 2014 Jul;387(7):641-8. doi: 10.1007/s00210-014-0976-2. Epub 2014 Mar 28.
Cyclic guanosine 3',5'-monophosphate (cGMP) inhibited the generation of pacemaker activity in interstitial cells of Cajal (ICCs) from the small intestine. However, cGMP role on pacemaker activity in colonic ICCs has not been reported yet. Thus, we investigated the role of cGMP in pacemaker activity regulation by colonic ICCs. We performed a whole-cell patch-clamp and Ca(2+) imaging in cultured ICCs from mouse colon. 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, an inhibitor of guanylate cyclase) increased the pacemaker potential frequency, whereas zaprinast (an inhibitor of phosphodiesterase) and cell-permeable 8-bromo-cGMP decreased the pacemaker potential frequency. KT-5823 (an inhibitor of protein kinase G [PKG]) did not affect the pacemaker potential. L-N(G)-nitroarginine methyl ester (L-NAME, an inhibitor of nitric oxide [NO] synthase) increased the pacemaker potential frequency, whereas (±)-S-nitroso-N-acetylpenicillamine (SNAP, a NO donor) decreased the pacemaker potential frequency. Glibenclamide (an ATP-sensitive K(+) channel blocker) did not block the effects of cell-permeable 8-bromo-cGMP and SNAP. Recordings of spontaneous intracellular Ca(2+) ([Ca(2+)]i) oscillations revealed that ODQ and L-NAME increased [Ca(2+)]i oscillations. In contrast, zaprinast, 8-bromo cGMP, and SNAP decreased the [Ca(2+)]i oscillations. Basal cGMP levels regulate the resting pacemaker potential frequency by the alteration on Ca(2+) release via a PKG-independent pathway. Additionally, the endogenous release of NO seems to be responsible maintaining basal cGMP levels in colonic ICCs.
环磷酸鸟苷（cGMP）可抑制小肠中Cajal间质细胞（ICC）起搏活动的产生。然而，cGMP对结肠ICC起搏活动的作用尚未见报道。因此，我们研究了cGMP在结肠ICC调节起搏活动中的作用。我们对从小鼠结肠分离培养的ICC进行了全细胞膜片钳和Ca(2+)成像实验。1H-[1,2,4]恶二唑并[4,3-a]喹喔啉-1-酮（ODQ，一种鸟苷酸环化酶抑制剂）可增加起搏电位频率，而扎普司特（一种磷酸二酯酶抑制剂）和细胞可渗透的8-溴-cGMP可降低起搏电位频率。KT-5823（一种蛋白激酶G [PKG]抑制剂）对起搏电位无影响。L-N(G)-硝基精氨酸甲酯（L-NAME，一种一氧化氮[NO]合酶抑制剂）可增加起搏电位频率，而(±)-S-亚硝基-N-乙酰青霉胺（SNAP，一种NO供体）可降低起搏电位频率。格列本脲（一种ATP敏感性钾通道阻滞剂）不阻断细胞可渗透的8-溴-cGMP和SNAP的作用。自发性细胞内Ca(2+)（[Ca(2+)]i）振荡记录显示，ODQ和L-NAME可增加[Ca(2+)]i振荡。相反，扎普司特、8-溴-cGMP和SNAP可降低[Ca(2+)]i振荡。基础cGMP水平通过不依赖PKG的途径改变Ca(2+)释放来调节静息起搏电位频率。此外，内源性NO释放似乎负责维持结肠ICC中的基础cGMP水平。
