Abstract
Principal differences in the kinetics and amplitude of Ca2+ response to norepinephrine were found between freshly isolated young differentiated brown fat cells. An increase in the Ca2+ concentration in the cytoplasm ([Ca2+]i) in the young cells was unusually slow (A[Ca2+]i = 0.03 nM/s) in comparison with that in the differentiated cells, and the Ca2+ influx from the outside was not induced by Ca2+ mobilization agents, such as thapsigargin and ionomycin. Ionomycin increased [Ca2+]i up to 150 nM in a Ca2+-free medium and up to 270 nM in the normal medium. This results in that the intracellular Ca2+ stores in freshly isolated young cells are rather poor, and the mechanism of capacitive calcium entry does not virtually function. The data on chemical modification of Ca2+ channels in the plasma membrane by thimerosal suggest that the conductance of these channels is low and/or their number in young brown fat cells is insignificant.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adipocytes / drug effects*
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Adipocytes / metabolism*
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Adipocytes / ultrastructure
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Adipose Tissue, Brown / drug effects*
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Adipose Tissue, Brown / metabolism*
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Adipose Tissue, Brown / ultrastructure
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Animals
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Calcium / metabolism
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Calcium Channels / drug effects
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Calcium Channels / metabolism
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Calcium Signaling / drug effects
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Calcium Signaling / physiology
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Calcium-Binding Proteins / drug effects*
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Calcium-Binding Proteins / metabolism*
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Cell Membrane / drug effects
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Cell Membrane / metabolism
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Cytosol / drug effects
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Cytosol / metabolism
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Endoplasmic Reticulum / drug effects
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Endoplasmic Reticulum / metabolism
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Endoplasmic Reticulum / ultrastructure
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Kinetics
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Male
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Mice
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Mice, Inbred Strains / metabolism
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Norepinephrine / metabolism
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Norepinephrine / pharmacology
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Thapsigargin / pharmacology
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Thimerosal / pharmacology
Substances
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Calcium Channels
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Calcium-Binding Proteins
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Thimerosal
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Thapsigargin
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Calcium
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Norepinephrine