Rhythmic oscillations of cytosolic free calcium in rat C-cells

The relationship between stimulation of single C-cells (rMTC-6-23 cell line) with extracellular calcium, glucagon or 8-bromo-cAMP and fluctuations of intracellular free calcium concentration was studied. After pretreatment of rMTC cells with either 1 microM glucagon (30-60 min) or 1 mM 8-bromo-cAMP (5 min) [Ca2+]i started to oscillate when extracellular calcium was raised to 3 mM. These fluctuations in [Ca2+]i could be stopped by chelating the external calcium with EGTA or by adding calcium channel blockers. The voltage-dependent calcium channels in the plasma membrane seem to play a major role in maintaining the oscillations of [Ca2+]i.