Ca2+ and cAMP activate different chloride efflux pathways in HT-29.cl19A colonic epithelial cell line

A B Vaandrager, R Bajnath, J A Groot, A G Bot, H R De Jonge

    Research output: Contribution to journalArticleAcademicpeer-review


    The mechanism of adenosine 3',5'-cyclic monophosphate (cAMP)- and Ca(2+)-induced Cl- secretion was studied in monolayers of the colon carcinoma cell line HT-29.cl19A by combined short-circuit current (Isc) and 125I- or 36Cl- efflux measurements. Forskolin, a specific adenylate cyclase activator, was found to induce a large increase in Isc and a two- to threefold increase in 36Cl- efflux solely across the apical border. The fractional efflux of 36Cl-compared with 125I- (basal ratio 1.71 +/- 0.28) did not change significantly in the presence of forskolin (1.91 +/- 0.45). In contrast, the Ca2+ ionophore A23187 did not appreciably affect the Isc but enhanced 36Cl- and 125I- efflux at the apical and basolateral side of the monolayer. Furthermore, the fractional efflux ratio of 36Cl- to 125I- changed dramatically to a value of 0.36 +/- 0.14. Both forskolin- and A23187-induced 36Cl- or 125I- efflux were only weakly inhibited by the putative Cl- channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoicacid. Carbachol, a Ca(2+)-linked agonist, mimicked the effects of A23187 on the 36Cl- and 125I- efflux but additionally provoked a significant increase in Isc. These data show that Ca2+ and cAMP activate different Cl-efflux pathways in HT-29.cl19A cells. Most likely these pathways represent a cAMP-activated conductance in the apical membrane and a separate Ca(2+)-activated Cl- conductance expressed in both apical and basolateral membranes. Apparently cholinergic agonists induce net electrogenic Cl- secretion through an intracellular signaling pathway (e.g., protein kinase C activation) different from the one activated by Ca2+/Ca2+ ionophore alone.

    Original languageEnglish
    Pages (from-to)G958-65
    JournalAmerican Journal of Physiology
    Issue number6 Pt 1
    Publication statusPublished - Dec 1991


    • Biological Transport
    • Calcimycin
    • Calcium
    • Calcium Channel Blockers
    • Carbachol
    • Chlorides
    • Colforsin
    • Colon
    • Colonic Neoplasms
    • Cyclic AMP
    • Epithelium
    • Humans
    • Iodides
    • Kinetics
    • Potassium
    • Signal Transduction
    • Tumor Cells, Cultured


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