Milovic V, Faust D, Turchanowa L, Stein J, Caspary W F
Second Department of Medicine, Johann Wolfgang Goethe University, Frankfurt, Germany.
Nutrition. 2001 Jun;17(6):462-6. doi: 10.1016/s0899-9007(01)00514-7.
The polyamines putrescine, spermidine, and spermine are present in foods in high amounts, and are used for cell growth throughout the body. Surprisingly little is known about the mechanisms of polyamine absorption in the gut. To elucidate the mechanisms, transepithelial transport of polyamines was studied in human enterocytelike Caco-2 cells, grown on permeable filter supports. Transport of all three polyamines across Caco-2 cell monolayers was linear; intraepithelial accumulation of polyamines was higher in confluent than in differentiated Caco-2 cells, but still negligible in comparison with the overall transport across the monolayers. Epidermal growth factor (EGF) enhanced polyamine accumulation in Caco-2 cells four-fold, and basolateral uptake was higher than apical uptake if the cells were stimulated to grow. The amounts of polyamines taken up by the cells were nevertheless negligible in comparison with the net polyamine flux across the monolayers. Basolateral excretion of polyamines was in the picomolar range, whereas their transepithelial transport, occurring presumably by passive diffusion through the paracellular pathway, contributed hundreds of micromoles of polyamines to the basolateral chamber. We conclude that transepithelial transport of polyamines occurs by passive diffusion, and that it is not influenced when epithelial cells are stimulated to proliferate by a potent mitogen such as EGF.
多胺腐胺、亚精胺和精胺在食物中含量很高，并用于全身的细胞生长。令人惊讶的是，人们对肠道中多胺吸收的机制知之甚少。为了阐明这些机制，在生长于可渗透滤膜支架上的人肠上皮样Caco-2细胞中研究了多胺的跨上皮转运。所有三种多胺跨Caco-2细胞单层的转运呈线性；汇合的Caco-2细胞中多胺的上皮内积累高于分化的Caco-2细胞，但与跨单层的总体转运相比仍然可以忽略不计。表皮生长因子（EGF）使Caco-2细胞中的多胺积累增加了四倍，如果刺激细胞生长，基底外侧摄取高于顶端摄取。然而，与跨单层的净多胺通量相比，细胞摄取的多胺量仍然可以忽略不计。多胺的基底外侧排泄处于皮摩尔范围内，而它们的跨上皮转运可能是通过细胞旁途径的被动扩散发生的，为基底外侧腔室贡献了数百微摩尔的多胺。我们得出结论，多胺的跨上皮转运是通过被动扩散发生的，并且当上皮细胞被强效有丝分裂原如EGF刺激增殖时，它不受影响。
