Electrical bursting and luminal calcium oscillation in excitable cell models

Abstract.

 It is shown in this paper that electrical bursting and the oscillations in the intracellular calcium concentration, [Ca²⁺]_i, observed in excitable cells such as pancreatic β-cells and R-15 cells of the mollusk Aplysia may be driven by a slow oscillation of the calcium concentration in the lumen of the endoplasmic reticulum, [Ca²⁺]_lum. This hypothesis follows from the inclusion of the dynamic changes of [Ca²⁺]_lum in the Chay bursting model. This extended model provides answers to some puzzling phenomena, such as why isolated single pancreatic β-cells burst with a low frequency while intact β-cells in an islet burst with a much higher frequency. Verification of the model prediction that [Ca²⁺]_lum is a primary oscillator which drives electrical bursting and [Ca²⁺]_i oscillations in these cells awaits experimental testing. Experiments using fluorescent dyes such as mag-fura-2-AM or aequorin could provide relevant information.