Kita Kazutomo, Takahashi Kento, Ohashi Yumi, Takasuka Hironori, Aihara Eitaro, Takeuchi Koji
Division of Pathological Sciences, Department of Pharmacology and Experimental Therapeutics, Kyoto Pharmaceutical University, Misasagi, Yamashina, Kyoto 607-8414, Japan.
J Pharmacol Exp Ther. 2008 Sep;326(3):889-96. doi: 10.1124/jpet.108.138941. Epub 2008 Jun 12.
(+/-)-(E)-4-Ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide] (NOR-3), a nitric-oxide (NO) donor, is known to increase HCO(3)(-) secretion in rat stomachs, intracellularly mediated by cGMP; yet, there is no information about the phosphodiesterase (PDE) isozyme involved in this process. We examined the effects of various isozyme-selective PDE inhibitors on the secretion of HCO(3)(-) in the mouse stomach in vitro and the type(s) of PDE isozymes involved in the response to NO. The gastric mucosa of DDY mice was stripped of the muscle layer and mounted on an Ussing chamber. HCO(3)(-) secretion was measured at pH 7.0 using a pH-stat method and by adding 2 mM HCl. NOR-3, 8-bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP), and various PDE inhibitors were added to the serosal side. Vinpocetine (PDE1 inhibitor) or zaprinast (PDE5 inhibitor) was also added serosally 30 min before NOR-3 or 8-Br-cGMP. Both NOR-3 and 8-Br-cGMP stimulated HCO(3)(-) secretion in a dose-dependent manner, and the response to NOR-3 was significantly inhibited by methylene blue. Likewise, the secretion induced by NOR-3 or 8-Br-cGMP was significantly attenuated by 6-((2S,3S)-3-(4-chloro-2-methylphenylsulfonylaminomethyl)-bicyclo(2.2.2)octan-2-yl)-5Z-hexenoic acid (ONO-8711), the PGE receptor (EP)1 antagonist, as well as indomethacin and potentiated by both vinpocetine and zaprinast at doses that had no effect by themselves on the basal secretion, whereas other subtype-selective PDE inhibitors had no effect. NOR-3 increased the mucosal PGE(2) content in a methylene blue-inhibitable manner. These results suggest that NO stimulates gastric HCO(3)(-) secretion mediated intracellularly by cGMP and modified by both PDE1 and PDE5, and this response is finally mediated by endogenous PGE(2) via the activation of EP1 receptors.
（±）-（E）-4-乙基-2-[(E)-羟基亚氨基]-5-硝基-3-己烯酰胺（NOR-3）是一种一氧化氮（NO）供体，已知其可增加大鼠胃中HCO₃⁻的分泌，这一过程由细胞内的环磷酸鸟苷（cGMP）介导；然而，关于参与此过程的磷酸二酯酶（PDE）同工酶尚无相关信息。我们研究了各种同工酶选择性PDE抑制剂对体外小鼠胃中HCO₃⁻分泌的影响以及参与对NO反应的PDE同工酶类型。将DDY小鼠的胃黏膜剥离肌肉层并安装在尤斯灌流小室上。使用pH计法并添加2 mM盐酸在pH 7.0条件下测量HCO₃⁻分泌。将NOR-3、8-溴鸟苷3',5'-环一磷酸（8-Br-cGMP）和各种PDE抑制剂添加到浆膜侧。长春西汀（PDE1抑制剂）或扎普司特（PDE5抑制剂）也在NOR-3或8-Br-cGMP前30分钟经浆膜侧添加。NOR-3和8-Br-cGMP均以剂量依赖性方式刺激HCO₃⁻分泌，且亚甲蓝可显著抑制对NOR-3的反应。同样，NOR-3或8-Br-cGMP诱导的分泌被PGE受体（EP）1拮抗剂6-((2S,3S)-3-(4-氯-2-甲基苯磺酰氨基甲基)-双环(2.2.2)辛烷-2-基)-5Z-己烯酸（ONO-8711）以及吲哚美辛显著减弱，而长春西汀和扎普司特在对基础分泌无影响的剂量下可增强该分泌，而其他亚型选择性PDE抑制剂则无作用。NOR-3以亚甲蓝可抑制的方式增加黏膜PGE₂含量。这些结果表明，NO刺激胃中HCO₃⁻分泌，该过程由cGMP在细胞内介导，并受到PDE1和PDE5的修饰，且这种反应最终由内源性PGE₂通过激活EP1受体介导。
