Reduction of the Ca2+ transport systems in mouse young brown fat cells.
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.
Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region.
L P
LP
Dolgacheva
E N
EN
Galitovskaya
G E
GE
Bronnikov
V P
VP
Zinchenko
D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D002001:Adipose Tissue, Brown / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000187:drug effects* / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D007700:Kinetics; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D013849:Thimerosal / Q000494:pharmacology
D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D013849:Thimerosal; D019284:Thapsigargin; D002118:Calcium; D009638:Norepinephrine