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Permeability of cell junction depends on local cytoplasmic calcium activity

Naturevolume 254pages250252 (1975) | Download Citation

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Abstract

MANY kinds of cells are coupled by junctions consisting of membrane channels through which molecules of a certain size range can flow freely from one cell interior to another1. It has been proposed that the permeability of the junctional channels depends on the concentration of free ionised calcium in cytoplasm ([Ca2+]i) (ref. 2). This hypothesis is supported by two classes of experiments. In one, the interior of a coupled cell system is allowed ito exchange freely with a known [Ca2+] in the exterior, through a hole in the (non-junctional) membrane; junctional conductance is reduced (uncoupling) when the [Ca2+]i is above 5–8 × 10−5 M (ref. 3). In the other class, uncoupling ensues when the (closed) cell system is treated with inhibitors of energy metabolism or with Ca2+ ionophores5, or on exposure for long periods to Ca,Mg-free medium or to Li medium6; in these conditions a rise in [Ca2+]i, may be expected because of known properties of cellular Ca metabolism7,8. Here, we demonstrate the changes in [Ca2+]i together with those in coupling in three of these conditions, using aequorin to display the distribution of Ca2+ in the cell. It will be shown that the uncoupling is, indeed, in each case associated with a rise in [Ca2+]. Furthermore, by local injection of Ca2+ into the cells, it will be shown that uncoupling ensues when the rise in [Ca2+]i occurs at the junction, but not when it occurs at other regions in the cell.

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Affiliations

  1. Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida, 33136

    • BIRGIT ROSE
    •  & WERNER R. LOEWENSTEIN

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https://doi.org/10.1038/254250a0

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