title: Cl- secretion in epithelial monolayers of mucus-forming human colon cells (HT-29/B6).
abstract: HT-29, an undifferentiated human colon cell line, is known to differentiate when cultured without glucose. This study aimed to characterize ion transport in the clone HT-29/B6, which was selected from HT-29 cells differentiated by glucose-free culture. HT-29/B6 cells seeded onto filter membranes grew as polarized monolayers, mainly consisting of mucus-forming cells and exhibiting high transepithelial resistance. Short-circuit current (Isc) of unstimulated HT-29/B6 monolayers in Ussing chambers was 0.1 +/- 0.01 mumol.h-1.cm-2, and conductance was 2.0 +/- 0.2 mS/cm2. Serosal forskolin (FSK; 10(-5) M) induced a sustained Isc of 1.9 +/- 0.1 mumol.h-1.cm-2, associated with a rise of intracellular adenosine 3',5'-cyclic monophosphate (cAMP). Isc was identified as Cl- secretion by tracer studies and by the inhibitory effects of serosal bumetanide and Ba2+. The Cl- channel blockers NPPB and DPC diminished FSK-induced Isc at respective doses of 3 x 10(-4) and 10(-3) M, being effective from either side of the monolayer. Cl- secretion could be triggered by vasoactive intestinal peptide (10(-8) M), prostaglandin E1 (10(-6) M), and dibutyryl cAMP (10(-3) M) as well. In conclusion, HT-29/B6 cells grow as polarized monolayers, forming mucus and secreting Cl- in response to secretagogues. This clone may not only serve as a model for investigation of cellular mechanisms of intestinal Cl- secretion but may also be helpful to elucidate the contribution of mucus cells to this process.
authors.affiliation: Institut für Klinische Physiologie, Klinikum Steglitz, Freien Universität Berlin, Germany.
authors.forename: K M
authors.initials: KM
authors.lastname: Kreusel
authors.forename: M
authors.initials: M
authors.lastname: Fromm
authors.forename: J D
authors.initials: JD
authors.lastname: Schulzke
authors.forename: U
authors.initials: U
authors.lastname: Hegel
mesh_terms: D000042:Absorption; D000527:Alprostadil / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D003106:Colon / Q000378:metabolism* / Q000473:pathology; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000473:pathology; D008855:Microscopy, Electron, Scanning; D009093:Mucus / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
chemical_list: D002712:Chlorides; D005576:Colforsin; D014660:Vasoactive Intestinal Peptide; D012964:Sodium; D000242:Cyclic AMP; D000527:Alprostadil