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Metal Selectivity of Exocytosis in α‐Toxin‐Permeabilized Bovine Chromaffin Cells
Author(s) -
Tomsig J. L.,
Suszkiw J. B.
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.66020644.x
Subject(s) - exocytosis , chemistry , secretion , cytosol , secretagogue , chromaffin cell , biophysics , catecholamine , biochemistry , endocrinology , adrenal medulla , biology , enzyme
Metal selectivity of exocytosis was analyzed by comparing the effects of polyvalent metal cations Ca 2+ , Ba 2+ , Sr 2+ , Pb 2+ , La 3+ , Cd 2+ , Co 2+ , Tb 3+ , Mn 2+ , and Zn 2+ on the release of norepinephrine (NE) from staphylococcal α‐toxin‐permeabilized bovine chromaffin cells. Pb 2+ , La 3+ , Cd 2+ , Sr 2+ , and Ba 2+ activated NE secretion accompanied by the release of intragranular dopamine β‐hydroxylase but not cytosolic lactate dehydrogenase, indicating the activation of the mechanism of exocytosis. The release triggered by saturating concentrations of Pb 2+ , La 3+ , Cd 2+ , and Sr 2+ was nonadditive with Ca 2+ , indicating a common site of action. In contrast, the Ba 2+ ‐evoked NE release was additive with Ca 2+ and the Ca 2+ agonists Pb 2+ , La 3+ , Cd 2+ , and Sr 2+ , suggesting that Ba 2+ activates secretion at a site distinct from the Ca 2+ receptor. In distinction to the NE release evoked by Pb 2+ , La 3+ , Cd 2+ , and Ba 2+ , the Sr 2+ ‐evoked NE release was associated with a significant elevation of Ca 2+ concentration in the medium and abolished by Ca 2+ chelation. This indicates that the secretagogue effect of Sr 2+ was indirect and secondary to the displacement of bound Ca 2+ . Co 2+ and Mn 2+ inhibited the NE release evoked by Ca 2+ , Sr 2+ , Pb 2+ , La 3+ , and Cd 2+ but had no effect on the Ba 2+ ‐dependent secretion. Tb 3+ and Zn 2+ were without effect on exocytosis.