Ion Transport Across Mammalian Small Intestine

Neutrophil migration across a cultured epithelial monolayer elicits a biphasic resistance response representing sequential effects on transcellular and paracellular pathways

“…Furthermore, since regulation of C1-secretion in "1"84 cells is highly comparable to that found in natural tracheal and intestinal epithelium (Dharmsathaphorn and Madara, 1990), this cell line has become a widely used model for mechanistic studies of CI-secretion. In disease states of the intestine, electrogenic CI-secretion is the basis of secretory diarrhea (Sullivan and Field, 1991). Since neutrophil transmigration across epithelia likely occurs in response to a mucosal threat (bacterial chemoattractants, etc.…”

Functional characterization of Cl-/HCO3- exchange in villous cells of the mouse ileum

“…Villous enterocytes in the small intestine demonstrate plasma membrane Cl − /HCO 3 − -exchange activity which is believed to be involved in absorbing NaCl by coupling with Na + /H + exchange, in protecting mucosa by mediating HCO 3 − secretion and in regulating the intracellular pH value (5,10,21,30,31). Three kinds of membrane Cl − /HCO 3 − exchangers have recently been identified in the mammalian small intestine, i.e., SLC26A6 (alias PAT1) , SLC26A3 (alias DRA) and AE2 (alias SLC4A2) (11,13,15,17,20,22,23,26,28,33).…”

Role of lateral intercellular space and sodium recirculation for isotonic transport in leaky epithelia

“…Further to this, it should be mentioned that mammalian intestine exhibits capacity for HCOf secretion (ileum) as well as HCOf absorption (jejunum). For studies and reviews on HCOf transport and this ion's regulatory role for other transporters we refer to White et al 1984, Hopfer and Liedtke 1987, and Sullivan and Field 1991 The cellular mechanism of intestinal cr secretion has been studied in short-circuited mammalian small intestine with experimentally elevated cellular [cyclicAMP] accomplished by stimulation of the adenylate cyclase, inhibition with theophylline of cyclicAMP-breakdown, or by adding a membrane permeable cyclicAMP analogue to the serosal bath. The early studies (Field et al 1968, Field 1971, Field 1974, Sheerin and Field 1975, Frizzell et al 1979 showed that these protocols may enhance the transepithelial secretory ion flows to such an extend that secretion, not absorption, of electrolytes becomes the dominating function.…”

“…In reviews by Madara (1991) and Sullivan and Field (1991), and in analogy with what has been suggested for the epithelium of large intestine (Welsh et al 1982), it was assumed that in the mammalian small intestine NaCl-absorption and uptake of nutrients are located to the surface cells whereas the secretory capacity is confined to the proliferating ('undifferentiated') crypt cells. This notion of functional heterogeneity among intestinal cells is supported by the finding that in situ hybridization in rat small intestine with 35S-radiolabelled probes of CFTR mRNA synthesized from rat cDNA (Trezise and Buchwall, 1991) and in human small intestine with ~SS-mRNA probes synthesized from hCFTR cDNA (Strong et al 1994) indicated in both species a decreasing expression of CFTR from the crypt cells to the surface cells.…”