Comparative analysis of Ca2+-signaling in brown preadipocytes of the ground squirrel (Spermophillus undulatus) and mouse

We compared the Ca2+ response to noradrenalin, tapsigargin, thimerosal, and ionomycin in brown preadipocytes of the ground squirrel (Spermophillus undulatus) and mouse. The ground-squirrel brown preadipocytes did not respond to noradrenalin in concentrations within the physiological range. Stimulation of the plasma membrane Ca2+-channels with thimerosal showed a considerable reduction of the calcium entry in cell precursors of the both species. Intracellular calcium stores liberated in the preadipocytes of the both species by tapsigargin and ionomycin in Ca2+-free medium were insignificant. Ca2+-entry in preadipocytes was not activated by the intracellular Ca2+-store depletion. The Ca2+ response of the ground squirrel brown preadipocytes was independent of an animal’s physiological state or annual seasons. Brown preadipocytes of ground squirrels (Spermophillus undulatus) may be considered to be high ionomycin-resistant cells with reduced Ca2+-signaling systems.