Schwörer H, Racké K, Kilbinger H
Neuroscience. 1987 Apr;21(1):297-303. doi: 10.1016/0306-4522(87)90340-x.
The spontaneous release of 5-hydroxytryptamine and its metabolite 5-hydroxyindoleacetic acid from the enterochromaffin cells of the small intestine into the portal circulation was investigated in vitro using the vascularly perfused ileum of the guinea-pig. The release of 5-hydroxytryptamine decreased by 70% in a calcium-free medium and by 35% in the presence of tetrodotoxin. Inhibition of monoamine oxidase activity by pargyline (100 microM) had no effect on the spontaneous release of 5-hydroxytryptamine although it caused a 75% reduction in the outflow of 5-hydroxyindoleacetic acid. Imipramine (1 microM), an inhibitor of neuronal uptake of 5-hydroxytryptamine, reduced the 5-hydroxyindoleacetic acid outflow by 57% and increased the release of 5-hydroxytryptamine by 66%. The combination of both drugs showed no additional effect. The tissue content of 5-hydroxytryptamine and its metabolite was not changed after perfusion with the precursor L-tryptophan or monofluoromethyldopa, an inhibitor of the L-aromatic amino acid decarboxylase. The results show that the spontaneous release of 5-hydroxytryptamine and its metabolite reflects largely calcium-dependent exocytotic release of the amine. "Neuronal uptake" (into aminergic and/or enterochromaffin cells) followed by deamination appears to be the main pathway of 5-hydroxytryptamine catabolism in the guinea-pig ileum.
利用豚鼠血管灌流回肠，在体外研究了小肠肠嗜铬细胞中5-羟色胺及其代谢产物5-羟吲哚乙酸向门静脉循环的自发释放。在无钙培养基中，5-羟色胺的释放减少了70%，在存在河豚毒素的情况下减少了35%。帕吉林（100微摩尔）抑制单胺氧化酶活性对5-羟色胺的自发释放没有影响，尽管它使5-羟吲哚乙酸的流出减少了75%。5-羟色胺神经元摄取抑制剂丙咪嗪（1微摩尔）使5-羟吲哚乙酸流出减少了57%，并使5-羟色胺的释放增加了66%。两种药物联合使用未显示出额外的效果。用前体L-色氨酸或L-芳香族氨基酸脱羧酶抑制剂单氟甲基多巴灌注后，5-羟色胺及其代谢产物的组织含量没有变化。结果表明，5-羟色胺及其代谢产物的自发释放很大程度上反映了胺的钙依赖性胞吐释放。“神经元摄取”（进入胺能和/或肠嗜铬细胞）后脱氨似乎是豚鼠回肠中5-羟色胺分解代谢的主要途径。
