Regulatory mechanisms of ion and water transport across the eel intestine

5-羟色胺（5-HT）、乙酰胆碱（ACh）和房钠肽（ANP）均能抑制鳗鲡肠道的NaCl和水分吸收，其中ANP的抑制作用最强。经8BrcGMP预处理后ANP的作用完全消失，表明ANP通过cGMP合成起作用。同样，5-HT似乎可以激活cAMP的合成，因为用8BrcAMP预处理后5-HT的抑制作用显著降低。乙酰胆碱似乎能增强细胞内Ca^<2+>浓度，但Ca^<2+>离子载体离子霉素的作用不足以模拟乙酰胆碱的作用，提示有其他介质参与。当肠受到电刺激时，Cl^-输运瞬间减少。阿托品（一种毒蕈碱类乙酰胆碱拮抗剂）和ICS-205930（一种5-羟色胺拮抗剂）抑制了70%的瞬时反应，表明70%的场刺激作用是由于ACh和5HT的释放。剩下的30%必须支付给其他监管机构。另一方面，肾上腺素（AD）增强了5-HT和ACh预处理后的NaCl和水分吸收。使用育亨宾（alpha_2受体拮抗剂）可完全消除AD的影响。此外，即使在8BrCAMP和离子蛋白存在的情况下，AD的作用仍然被观察到，这表明AD作用于camp后和ca ^<2+>后过程。从鳗鱼肠中提取了一种新的肽，但对离子和水的运输没有影响。鳗鱼肠五肽（EIPP, h - gly - phe - trp - asn - lysoh）增强了食管、胃、肠等消化道滑滑肌的收缩。

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.