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Regulatory mechanisms of ion and water transport across the eel intestine

离子和水穿过鳗鱼肠道运输的调节机制

基本信息

批准号：
02804062
负责人：
ANDO Masaki
金额：
$ 0.96万
依托单位：
Hiroshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

The NaCl and water absorption across the eel intestine was inhibited by serotonine (5-HT), acetylcholine (ACh) or atrial natriuretic peptide (ANP), ANP being the most potent inhibitor. The effects of ANP were completely abolished after pretreatment with 8BrcGMP, indicating that ANP acts through cGMP synthesis. Similarly, 5-HT seems to activate cAMP synthesis, since the inhibitory effects of 5-HT were significantly reduced after pretreatment with 8BrcAMP. ACh seems to enhance the intracellular Ca^<2+> concentration, however the effect of Ca^<2+> ionophore, ionom-ycin, was not sufficient to mimic the effect of ACh, suggesting involvement of other mediators.When the intestine was stimulated electnically, the Cl^- transport was reduced transiently. The transient response was inhibited by 70% with atropine, a muscarinic ACh antagonist, and ICS-205930, a 5-HT antagonist, indicating that 70% of the effect of field-stimulation is due to release of ACh and 5HT. The remainig 30% must-be due to other regulators.On the other hand, adrenaline (AD) enhanced the NaCl and water absorption after pretreatment with 5-HT and ACh. The effects of AD were completely abolished with yohimbine, alpha_2-receptor antagonist. Moreover, the effects of AD were still observed even in the presence of 8BrCAMP and ionomyein, suggesting that AD acts on a post-cAMP and post-Ca^<2+> process.A novel peptide was also extracted from the eel intestine, but had no effect on the ion and water transport. The eel intestinal pentapeptide (EIPP, H-Gly-Phe-Trp-Asn-Lys-OH) enhanced the contraction of the srnooth muscle in the digestive tract such as esophagus, stomach and intestine.

5-羟色胺（5-HT）、乙酰胆碱（ACh）和心钠素（ANP）均能抑制鳗鱼小肠对NaCl和水的吸收，其中ANP的抑制作用最强。8BrcGMP预处理后，ANP的作用完全消失，提示ANP通过cGMP合成发挥作用。同样，5-HT似乎激活cAMP合成，因为用8 BrcAMP预处理后5-HT的抑制作用显著降低。ACh似乎能增加细胞内Ca^2+浓度，但Ca^2+载体离子霉素的作用不足以模拟ACh的作用，提示有其他介质的参与。阿托品（一种毒蕈碱型ACh拮抗剂）和ICS-205930（一种5-HT拮抗剂）可抑制70%的瞬时反应，表明场刺激效应的70%是由于ACh和5-HT的释放。肾上腺素（adrenaline，AD）对5-HT和ACh预处理后的NaCl和水的吸收有促进作用。α_2受体拮抗剂育亨宾可完全消除AD的作用。此外，在8 BrCAMP和离子霉素存在下，AD的作用仍然存在，表明AD作用于cAMP后和Ca ^2+后过程。鳗肠五肽（EIPP，H-Gly-Phe-Trp-Asn-Lys-OH）对食管、胃、肠等消化道平滑肌的收缩有明显的促进作用。