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Depolarization evokes different patterns of calcium signals and exocytosis in bovine and mouse chromaffin cells: the role of mitochondria
Author(s) -
Alés E.,
Fuentealba J.,
García A. G.,
López M. G.
Publication year - 2005
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2004.03861.x
Subject(s) - depolarization , protonophore , exocytosis , calcium , mitochondrion , secretion , chromaffin cell , biology , cytosol , membrane potential , endocrinology , intracellular , medicine , calcium in biology , microbiology and biotechnology , biophysics , catecholamine , chemistry , adrenal medulla , biochemistry , enzyme
This study was planned on the assumptions that different high‐voltage activated calcium channels and/or the ability of mitochondria to take up Ca 2+ could be responsible for different cytosolic Ca 2+ concentrations ([Ca 2+ ] c ) and catecholamine release responses in adrenal chromaffin cells of bovine and mouse species. Short K + pulses (2–5 s, 70 m m K + ) increased [Ca 2+ ] c to a peak of about 1 µ m ; however, in bovine cells the decline was slower than in mouse cells. Secretory responses were faster in mouse but were otherwise quantitatively similar. Upon longer K + applications (1 min), elevations of [Ca 2+ ] c and secretion were prolonged in bovine cells; in contrast [Ca 2+ ] c in mouse cells declined three‐fold faster and failed to sustain a continued secretion. Confocal [Ca 2+ ] c imaging following a 50‐ms depolarizing pulse showed a similar Ca 2+ entry, but a rate of [Ca 2+ ] c increase and a maximum peak significantly higher in bovine cells; the rate of dissipation of the Ca 2+ wave was faster in the mouse. The mitochondrial protonophore CCCP (2 µ m ) halved the K + ‐evoked [Ca 2+ ] c and secretory signals in mouse cells, but had little affect on bovine responses. We conclude that the relative densities of L (15% in bovine and 50% in mouse) and P/Q Ca 2+ channels (50% in bovine and 15% in mouse) do not contribute to the observed differences; rather, the different intracellular distribution of Ca 2+ , which is strongly influenced by mitochondria, is responsible for a more sustained secretory response in bovine, and for a faster and more transient secretory response in mouse chromaffin cells. It seems that mitochondria near the plasmalemma sequester Ca 2+ more rapidly and efficiently in the mouse than in the bovine chromaffin cell.