Regulation of chloride secretion in HT29 cells studied by X-ray microanalysis
1997 (English)Doctoral thesis, comprehensive summary (Other academic)
Several aspects of Cl- secretion in epithelial cells were investigated. Methods to prepare cultured cellsfor X-ray microanalysis, in order to study volume-regulating chloride transport were evaluated. Inaddition, α2A-adrenergic, muscarinic cholinergic, and purinergic Cl- efflux as well as Cl- effluxregulated by G-protein coupled receptors in HT29 cells was investigated. The purpose of the studywas to describe the regulation of Cl- transport in intestinal epithelial cells.
Exposure of HT29 cells to a hypotonic solution resulted in regulatory volume decrease (RVD)accompanied by loss of K and Cl from the cells, whereas exposure to hypertonic solutions resultedin regulatory volume increase (RVI) coupled to gain of Na and Cl. Chloride channel blockers, suchas NPPB and DPC, blocked RVD, accompanied by a decrease in intracellular Na, Cl and Kconcentration, suggesting that chloride channels are important in volume regulating ion transport.
Stimulation with UTP or ATP mainly induced loss of Cl and Na from the cells, concurrent with an increase in Ca. The ion fluxes induced by UTP could be blocked by NPPB and alloxan (aninhibitor of adenylate cyclase), indicating that UTP-mediated Cl- secretion may occur through bothcAMP- and Ca2+-dependent pathways.
The agonists of muscarinic receptors, carbachol and acetylcholine, caused a decrease inintracellular Cl and K concentration. However, P-F-HHSiD, an antagonist of muscarinic 3 receptors,inhibited secretion induced by carbachol or acetylcholine, suggesting that the ion secretion is mediatedby muscarinic 3 receptors. Moreover, the ion secretion could be inhibited by U-73122, an inhibitorof phospholipase C (PLC), indicating that secretion may be regulated by the PLC/Ca2+ dependent pathway.
Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating polypeptide(PACAP) elicited Cl- and K+ efflux, whereas UK14,304 and somatostatin-14 were able to reverse VIPor PACAP induced secretion, giving rise to an increase in the content of intracellular Na and Cl. Theantisecretory effect of UK14,304 and somatostatin-14 is probably involved in the inhibition of bothadenylate cyclase and PLC pathways by relevant receptors coupled to Gi Use of U-73122 and alloxantogether inhibited PACAP-induced Cl- efflux, indicatingthat Cl- secretion may not only be mediatedby cAMP activated Cl- channels, but also by Ca2+ activated Cl- channels.
Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 1997. , 35 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 0282-7476 ; 732
Anatomy, epithelium, chloride channel, HT29 cells, ion transport, volume, X-ray
microanalysis, G-protein coupled receptors, α2-adrenoceptors, purinoceptors, muscarinic
Cell and Molecular Biology
Research subject Human Anatomy
IdentifiersURN: urn:nbn:se:uu:diva-1220ISBN: 91-554-4103-3OAI: oai:DiVA.org:uu-1220DiVA: diva2:160778
1997-12-19, Seminar room C3, Uppsala Biomedical Center, Uppsala, 09:15