Permeability characteristics of polyamines across intestinal epithelium using the Caco-2 monolayer system: Comparison between transepithelial flux and mitogen-stimulated uptake into epithelial cells

The polyamines putrescine, spermidine, and spermine are present in foods in high amounts, and are used for cell growth throughout the body. Surprising ly little is known about the mechanisms of polyamine absorption in the gut. To elucidate the mechanisms, transepithelial transport of polyamines was s tudied in human enterocytelike Caco-2 cells, grown on permeable filter supp orts. Transport of all three polyamines across Caco-2 cell monolayers was l inear; intraepithelial accumulation of polyamines was higher in confluent t han 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 negligib le in comparison with the net polyamine flux across the monolayers. Basolat eral excretion of polyamines was in the picomolar range, whereas their tran sepithelial transport, occurring presumably by passive diffusion through th e paracellular pathway, contributed hundreds of micromoles of polyamines to the basolateral chamber. We conclude that transepithelial transport of pol yamines occurs by passive diffusion, and that it is not influenced when epi thelial cells are stimulated to proliferate: by a potent mitogen such as EG F. (C) Elsevier Science Inc. 2001.