Abstract
Cytosolic Ca2+ (Ca2+c) clearance from adrenal chromaffin cells was studied by whole-cell patch clamp and indo-1 Ca2+ photometry after influx of Ca2+ through voltage-dependent Ca2+ channels. We isolated the rates of Ca2+c clearance by several mechanisms using combinations of the following agents (with their expected targets): Li+ or TEA substituted for Na+ (Na(+)-Ca2+ exchange), 1 mM La3+ applied after the depolarization (Na(+)-Ca2+ exchange and plasma membrane Ca(2+)-ATPase), 1 microM thapsigargin (pumping into reticular stores), and 2 microM carbonyl cyanide m-chlorophenylhydrazone (uptake into mitochondria). Remarkably, whenever [Ca2+]c rose above approximately 500 nM, Ca2+c clearance by mitochondria exceeded clearance by either Na(+)-Ca2+ exchange or the Ca2+ pumps of the plasma and reticular membranes. As [Ca2+]c fell again, Ca2+ reemerged from mitochondria, prolonging the final return to basal levels.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adrenal Medulla / cytology
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Adrenal Medulla / embryology
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Adrenal Medulla / metabolism*
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Animals
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Biological Transport / drug effects
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Biological Transport, Active / drug effects
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Calcium / metabolism*
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Calcium Channel Blockers / pharmacology
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Calcium-Transporting ATPases / antagonists & inhibitors
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Calcium-Transporting ATPases / metabolism*
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Carbonyl Cyanide m-Chlorophenyl Hydrazone / pharmacology
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Carrier Proteins / antagonists & inhibitors
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Carrier Proteins / metabolism*
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Cell Lineage
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Cells, Cultured
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Intracellular Fluid / metabolism
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Intracellular Membranes / drug effects
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Intracellular Membranes / metabolism
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Lanthanum / pharmacology
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Lithium / pharmacology
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Male
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Membrane Potentials / drug effects
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Mitochondria / physiology*
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Neural Crest
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Neurons / metabolism
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Patch-Clamp Techniques
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Rats
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Rats, Sprague-Dawley
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Sodium-Calcium Exchanger
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Terpenes / pharmacology
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Tetraethylammonium
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Tetraethylammonium Compounds / pharmacology
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Thapsigargin
Substances
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Calcium Channel Blockers
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Carrier Proteins
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Sodium-Calcium Exchanger
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Terpenes
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Tetraethylammonium Compounds
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Carbonyl Cyanide m-Chlorophenyl Hydrazone
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Tetraethylammonium
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Thapsigargin
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Lanthanum
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Lithium
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Calcium-Transporting ATPases
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Calcium