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Calcium Is Released by Exocytosis Together with Catecholamines from Bovine Adrenal Medullary Cells
Author(s) -
Grafenstein Hermann R. K.,
Powis David A.
Publication year - 1989
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 - 10.1111/j.1471-4159.1989.tb07352.x
Subject(s) - exocytosis , chromaffin cell , catecholamine , adrenal medulla , secretion , calcium , extracellular , stimulation , chemistry , medicine , calcium in biology , endocrinology , intracellular , microbiology and biotechnology , biology , biochemistry , organic chemistry
We have tested the hypothesis that exocytosis is a possible export route for calcium from bovine adrenal medullary cells. After prelabelling cells in primary tissue culture with 45 Ca, evoked 45 Ca export and catecholamine secretion show the same time course, a similar fraction of the total pool of 45 Ca and catecholamine is released), and the same concentrations of carbamylcholine or KCl are required for half‐maximal triggered release. Increasing the osmolality of the extracellular medium or treating the cells with botulinum toxin type D inhibits both evoked catecholamine secretion and 45 Ca export to the same extent without inhibiting 45 Ca influx. Incorporation of 45 Ca into chromaffin granules is very slow, however, and incorporated 45 Ca is not immediately releasable. 45 Ca entering the cell during short‐term stimulation is not found in the releasable pool during a second period of triggered secretion. Our data suggest that chromaffin granules are the largest pool of intracellular calcium in bovine adrenal medullary cells and that most of the calcium in chromaffin granules does not rapidly exchange with cytoplasmic Ca, but can be released directly by exocytosis. Exocytosis does not appear to play a major role in exporting Ca that enters the cell during short‐term stimulation.