ISSN:
1460-9568
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
This study was planned on the assumptions that different high-voltage activated calcium channels and/or the ability of mitochondria to take up Ca2+ could be responsible for different cytosolic Ca2+ concentrations ([Ca2+]c) and catecholamine release responses in adrenal chromaffin cells of bovine and mouse species. Short K+ pulses (2–5 s, 70 mm K+) increased [Ca2+]c to a peak of about 1 µm; 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 [Ca2+]c and secretion were prolonged in bovine cells; in contrast [Ca2+]c in mouse cells declined three-fold faster and failed to sustain a continued secretion. Confocal [Ca2+]c imaging following a 50-ms depolarizing pulse showed a similar Ca2+ entry, but a rate of [Ca2+]c increase and a maximum peak significantly higher in bovine cells; the rate of dissipation of the Ca2+ wave was faster in the mouse. The mitochondrial protonophore CCCP (2 µm) halved the K+-evoked [Ca2+]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 Ca2+ channels (50% in bovine and 15% in mouse) do not contribute to the observed differences; rather, the different intracellular distribution of Ca2+, 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 Ca2+ more rapidly and efficiently in the mouse than in the bovine chromaffin cell.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1460-9568.2004.03861.x
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