Intestinal secretion morphology

Other cell lines used in permeability studies include the T84 human colonic adenocarcinoma colonic crypt cell model. This line has a reduced carrier expression, secrets mucus, and has very high resistance [31, 32], The IEC cell line is a rat fetal intestinal epithelium cell with higher permeabilities than Caco-2 cells [33], LLC PKi is a pig kidney epithelial cell line with low expression of efflux systems, but expression systems for transport proteins [32], 2/4/A1 cells are a conditionally immortalized rat fetal intestinal epithelium line with crypt cell-like morphology and temperature-sensitive differentiation [34], They form differentiated monolayers with tight junctions, increased brush border enzymes when grown on extracellular matrices with laminin. Transport of drugs with LP in 2/4/A1 monolayers was comparable to that in the human jejunum and up to 300 times faster than that in Caco-2 monolayers. In contrast, the permeability of HP drugs was comparable in both cell lines [34],... 

Madara, J.L. Functional morphology of epithelium of the small intestine. In Intestinal Absorption and Secretion Field, M., Raymond, A.F., Eds. American Physiological Society, 1991 IV, 83-120. 

Morphological studies have demonstrated the presence of cells in the GI tract that contain dopamine and express components of dopamine signaling pathways, including catecholamine biosynthetic enzymes and specific dopamine receptors and transporters. In tlie stomach, tyrosine hydroxylase is expressed in epithelial cells, including acid-secreting parietal cells. In the small intestine, cells of the lamina propria, including immune cells, also express tyro-... 

The major components of the gastrointestinal tract are the stomach, the small intestine, and the large intestine or colon (Fig. 30.2). The small intestine includes the duodenum, jejunum and ileum. The major segments of the gastrointestinal tract differ from one another both anatomically and morphologically, as well as with respect to secretions and pH. 

---