Larina O. The functioning of exocrine secretory cell membrane Na+-Ca2+ exchanger in forward and reverse modes

The dissertation is devoted to investigations of functioning of secretory cell plasma mem-brane Na+-Ca2+ exchanger of Chironomus plumosus L. salivary glands in forward and reverse modes. The outward current was identified that develops in response to membrane depolari-zation and reflects Na+-Ca2+ exchanger functioning in reverse mode. The dependence of this current on Na+ ion transport driving force and [Ca2+]i was identified. It was shown that changes of inward and outward Na+-Ca2+ exchange currents, which were evoked by ph level changes, are similar. It testifies that of cation bounding and translocation at Na+-Ca2+ ex-changer functioning in forward and reverse modes are similar. The effect of solution acidifi-cation testifies the participation of Asp and Glu COO--groups in these processes. It was also shown that SH-groups of intracellular parts of exchanger molecule play important role in its functioning in forward and reverse modes. The dependence of Ca2+ content in cell tissue on presence of NO donors in incubation medium was found and the possibility, that NO exerts its influence on secretory cell functioning via Na+-Ca2+ exchanger, was confirmed. The depend-ence of amplitudes of inward and outward Na+-Ca2+ exchange currents on sodium nitroprus-side concentration in presence and absence of SH-groups blockader was found. Its analysis permits to suppose that NO can exert its influence on Na+-Ca2+ exchanger functioning di-rectly, effecting SH-groups of aminoacid groups of its molecule. The scheme of Na+-Ca2+ exchanger functioning in forward and reverse modes was proposed.