COMPARATIVE ANALYSIS OF Ca2+-SIGNALLING IN BROWN PREADIPOCYTES
OF GROUND SQUIRREL SPERMOPHILLUS UNDULATUS AND MOUSE
L. P. Dolgacheva,1 M. V. Konakov, T. A. Agafonova, V. V. Rybina, V. P. Zinchenko,
G. E. Bronnikov
Institute of Cell Biophysics RAS, Pushchino, Moscow Region;
1 e-mail: dolgacheva@mail.ru
Analysis of the slow Ca2+-responses of brown preadipocytes of ground squirrel Spermophillus
undulatus and mouse was carried out. The mouse brown preadipocytes demonstrated low but prominent responses
to noradrenalin with the maximum at 3 and 10 μM being the less effective. The ground squirrel brown
preadipocytes practically did not practically respond to 10 nM-10 μM, whereas 30-600 μM noradrenalin was
able to raise intracellular [Ca2+]i up to 600 nM with 300 μM agonist being the most
effective. Stimulation of the plasma membrane Ca2+-channels with thimerosal showed considerable reduction
of the calcium entry system in the cell precursors of both species comparing with their mature adipocytes.
Intracellular calcium stores liberated in preadipocytes of both species by tapsigargin and ionomycin in
Ca2+-free medium were insignificant, and capacitative Ca2+-entry in response to the cellular
Ca2+-stores depletion was completely absent in Ca2+-containing medium. The
Ca2+-responses of the ground squirrel brown preadipocytes were independent on physiological state of
the animals and annual seasons. Preadipocytes of both species showed the same dose-response curves for the
Ca2+-raise under thimerosal, and the mouse had two-fold higher kinetic constants for the Ca2+
ions entry. The ground squirrel brown adipocytes responded to ionomycin with ≈25 % higher increase in
[Ca2+]i and the entry of the ions had 7-10-fold higher kinetic constants for this process.
Kinetic constants for the [Ca2+]i raise in mouse preadipocytes were independent of ionomycin
concentration, whereas in the ground squirrel brown preadipocytes the constant linearly increased with the ionophore
concentration. It is suggested that the found difference in the function of Ca2+-signalling in
preadipocytes of two species, which becomes apparent in the presence of ionomycin, might be responsible for the
observed difference in the noradrenalin induced cellular Ca2+-responses as well.
Key words: brown preadipocytes, noradrenalin, acclimation to cold, hibernation,
Ca2+-signaling system
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