Effect of extracellular Ca2+ on plasma membrane Ca2+ inflow and cytoplasmic free Ca2+ in isolated hepatocytes

Bernard P. Hughes, Amanda M. Auld, Gregory J. Barritt

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    10 Citations (Scopus)

    Abstract

    An initial rapid phase and a subsequent slow phase of 45Ca2+ uptake were observed following the addition of 45Ca2+ to Ca2+-deprived hepatocytes. The magnitude of the rapid phase increased 15-fold over the range 0.1-11 mM extracellular Ca2+ (Ca2+o) and was a linear function of [Ca2+]o. The increases in the rate of 45Ca2+ uptake were accompanied by only small increases in the intracellular free Ca2+ concentration. In cells made permeable to Ca2+ by treatment with saponin, the rate of 45Ca2+ uptake (measured at free Ca2+ concentrations equal to those in the cytoplasm of intact cells) increased as the concentration of saponin increased from 1.4 to 2.5 μg per mg wet weight cells. Rates of 45Ca2+ uptake by cells permeabilized with an optimal concentration of saponin were comparable with those of intact cells incubated at physiological [Ca2+o], but were substantially lower than those for intact cells incubated at high [Ca2+o]. It is concluded that (i) Ca2+ which enters the hepatocyte across the plasma membrane is rapidly removed by binding and transport to intracellular sites and by the plasma membrane Ca2+ + Mg2+-ATPase and (ii) the plasma membrane Ca2+ inflow transporter is not readily saturated with Ca2+o.

    Original languageEnglish
    Pages (from-to)208-216
    Number of pages9
    JournalBBA - Molecular Cell Research
    Volume928
    Issue number2
    DOIs
    Publication statusPublished - 22 Apr 1987

    Keywords

    • (Hepatocyte plasma membrane)
    • Calcium ion inflow
    • Calcium ion, cytoplasmic
    • Permeability

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