ATP-stimulated Ca2+-activated K+ efflux pathway and differentiation of human placental cytotrophoblast cells

L. H. Clarson, V. H.J. Roberts, S. L. Greenwood, A. C. Elliott

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    16 Scopus citations

    Abstract

    The aim of this study was to determine whether extracellular ATP ([ATP]o) stimulated a Ca2+-activated K+ efflux in trophoblast cells that was dependent on extracellular Ca2+ ([Ca2+]o). Cytotrophoblast cells, isolated from human placenta, were examined following 18 h (relatively undifferentiated) and 66 h (multinucleate cells) of culture. Potassium efflux was measured using 86Rb as a trace marker. Intracellular Ca2+ ([Ca2+]i) was examined by microfluorometry using fura 2. [ATP]o significantly increased 86Rb efflux to a peak that declined to control (18-h cells) or an elevated plateau (66-h cells) and was inhibited by 100 nM charybdotoxin. Removing [Ca2+]o significantly reduced 86Rb efflux in both groups as did application of 150 μM GdCl3. [ATP]o significantly increased [Ca2+]i in both groups of cells. The response was reduced by removing [Ca2+]o and applying 150 μM GdCl3. For both 86Rb efflux and microfluorometry experiments, the response to [ATP]o was more dependent on [Ca2+]o in 66-h cells compared with 18-h cells (∼70% greater). Cytotrophoblast cells exhibit an [ATP]o-stimulated Ca2+-activated K+ efflux. The dependency of this pathway on [Ca2+]o is greater in the 66-h multinucleate syncytiotrophoblast-like cells, suggesting that the mechanism for Ca2+ entry may be altered during differentiation of trophoblast cells.

    Original languageEnglish (US)
    Pages (from-to)R1077-R1085
    JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
    Volume282
    Issue number4 51-4
    DOIs
    StatePublished - 2002

    Keywords

    • Calcium entry
    • Human placenta
    • Intermediate calcium-activated potassium channel

    ASJC Scopus subject areas

    • Physiology
    • Physiology (medical)

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