Objective: 

In secretory cells, changes in intracellular calcium concentration [Ca²⁺]_i couple cell activation with hormone secretion.

Methods: 

By employing confocal microscopy, we were able to resolve dynamics of [Ca²⁺]_i in individual islet cells within the pancreas tissue slices as a function of time and space.

Results: 

Activity patterns of a large number of individual cells per islet, subregions of the islet, as well as the whole islet were analyzed following administration of various physiological stimuli and modulators of calcium membrane transport. Patterns of [Ca²⁺]_i oscillations in response to glucose have been heterogeneous. Increasing concentrations of glucose progressively recruited individual cells and later groups of cells, with progressively increasing frequency and synchronicity. However, the time in which each group of cells oscillated as a functional cluster appeared to be limited and the clusters changed constantly in terms of their position inside the islet and the number of cells they included. Synchronous activity was strongly influenced by extracellularly applied Ba²⁺ and Cd²⁺, indicating that extracellular Ca²⁺ contributed to oscillatory activity.

Conclusion: In the present work, the properties of experimentally obtained islet cell networks were also compared with the theoretical network model of spatially embedded heterogeneous cells to gain new insights into the relationship between structure and function of the tissue.