Furukawa O, Kawauchi S, Mimaki H, Takeuchi K
Department of Pharmacology & Experimental Therapeutics, Kyoto Pharmaceutical University, Misasagi, Yamashina, Kyoto 607-8414, Japan.
Med Sci Monit. 2000 May-Jun;6(3):454-9.
The effect of nitric oxide (NO) on HCO3- secretion was examined in vitro using the isolated preparation of bullfrog duodenum, in relation to cyclooxygenase (COX) isozymes and endogenous prostaglandins (PGs). The tissue was bathed in unbuffered Ringer solution gassed with 100% O2 on the mucosal side and HCO3- Ringer's solution gassed with 95% O2-5% CO2 on the serosal side. The HCO3- secretion was measured by a pH-stat method using 10 mM HCl as the titrant to keep the mucosal pH at 7.4. NOR-3 [(+/-)-(E)-Ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamine] was used as a NO donor and added to the serosal solution. To analyze the NOR-3 action, the effects of dibutyryl guanosine-3', 5'-cyclic monophosphate (dbcGMP), methylene blue, indomethacin (nonselective COX-inhibitor) and NS-398 (selective COX-2 inhibitor) on the HCO3- response were also examined. NOR-3 (1 x 10(-4) and 3 x 10(-4) M) caused an increase of HCO3- secretion in a dose-dependent manner, reaching the level of 2.5 times greater than basal values at 2 hr later. Likewise, dbcGMP (1 x 10(-3) M) also caused a significant increase of the duodenal HCO3- secretion. The HCO3- stimulatory action of NOR-3 was significantly attenuated by methylene blue (5 x 10(-5) M) and indomethacin (1 x 10(-5) M) but not by NS-398 (1 x 10(-5) M), and indomethacin also suppressed the HCO3- response to dbcGMP. The serosal release of PGE2 was significantly increased by both NOR-3 and dbcGMP, and these responses were inhibited by indomethacin but not NS-398. These results suggest that NO increases HCO3- secretion in Bullfrog duodenum in vitro, and this action is dependent on cGMP-related COX-1 activation and mediated by PGs.
利用牛蛙十二指肠的离体标本，研究了一氧化氮（NO）对HCO₃⁻分泌的影响，并探讨了其与环氧化酶（COX）同工酶及内源性前列腺素（PGs）的关系。将组织置于黏膜侧用100% O₂充气的无缓冲林格氏液中，浆膜侧用95% O₂ - 5% CO₂充气的HCO₃⁻林格氏液中。采用pH计法，以10 mM HCl作为滴定剂来维持黏膜pH值为7.4，以此测量HCO₃⁻分泌。使用NOR - 3 [（±）-（E）-乙基-2- [（E）-羟基亚氨基]-5-硝基-3-己烯胺]作为NO供体，并添加到浆膜溶液中。为分析NOR - 3的作用，还研究了二丁酰鸟苷-3'，5'-环磷酸（dbcGMP）、亚甲蓝、吲哚美辛（非选择性COX抑制剂）和NS - 398（选择性COX - 2抑制剂）对HCO₃⁻反应的影响。NOR - 3（1×10⁻⁴和3×10⁻⁴ M）以剂量依赖方式引起HCO₃⁻分泌增加，2小时后达到比基础值高2.5倍的水平。同样，dbcGMP（1×10⁻³ M）也显著增加十二指肠HCO₃⁻分泌。NOR - 3对HCO₃⁻的刺激作用被亚甲蓝（5×10⁻⁵ M）和吲哚美辛（1×10⁻⁵ M）显著减弱，但不受NS - 398（1×10⁻⁵ M）影响，吲哚美辛也抑制了对dbcGMP的HCO₃⁻反应。NOR - 3和dbcGMP均显著增加了PGE₂的浆膜释放，且这些反应被吲哚美辛抑制，但不受NS - 398抑制。这些结果表明，NO在体外增加牛蛙十二指肠的HCO₃⁻分泌，且该作用依赖于cGMP相关的COX - 1激活，并由PGs介导。
