Epithelial cells major compounds transported

Drugs can cross the intestinal epithelial barrier in a number of ways. They may permeate either through the cell (transcellular) or between adjacent cells (para-cellular). Enterocytes have tight intercellular junctions that restrict paracellular transport to small hydrophilic molecules.7 These cells possess active and facilita-tive transporters for nutrients, as well as an array of efflux transporters [e.g., P-glycoprotein (P-gp) and related transporters] and enzymes (e.g., cytochrome P450 type 3A4) that restrict transcellular absorption. Transcytotic transport of macromolecules is possible, but compounds are often destroyed in lysosomes. With the exception of M-cells, transcytosis is not considered a major mechanism of the transcellular pathway for absorption of macromolecules across gastrointestinal epithelium.6... 

The major absorption of tea catechins is the small intestine. EC, ECG, EGC, and EGCG were disposed at the intestinal epithelium by similar efflux and metabolism mechanisms. Intestinal epithelial membrane transport of catechins was studied via perfusion of EC and ECG in the human Caco-2 cell line. - The absorption and secretion transports of the four catechins, in the form of individual pure compounds, pure compound mixtures, and green tea extract, were studied in the human Caco-2 cell model. The results showed that the absorption transport of the four catechins in different doses was similar, but the green tea polyphenol mixtures could affect the secretion transport of individual catechins. It was suggested that the transporter competition may be responsible for the reduced efflux of EC, and metabolic competition may bring about a reduction in the formation of EGC sulfate and methylated EGC sulfate. ... 

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