The Ca2+ dynamics of isolated mouse beta-cells and islets: implications for mathematical models

Area of Science:

• Cell Biology
• Physiology
• Biophysics

Background:

• Pancreatic islets and isolated beta-cells exhibit distinct intracellular calcium ([Ca(2+)](i)) dynamics.
• Understanding these differences is crucial for elucidating glucose-stimulated insulin secretion mechanisms.

Purpose of the Study:

• To compare [Ca(2+)](i) signaling and electrical activity in isolated beta-cells and islets.
• To investigate the role of electrical activity in generating observed [Ca(2+)](i) patterns.
• To validate a computational model for [Ca(2+)](i) dynamics.

Main Methods:

• Standard electrophysiological techniques for simultaneous recording of [Ca(2+)](i) and membrane potential.
• Glucose stimulation protocols.
• Dynamic clamp to alter beta-cell electrical activity.
• Computational modeling.

Main Results:

• Islets displayed glucose-induced [Ca(2+)](i) oscillations (fast, slow, or mixed), while isolated beta-cells showed faster, more irregular [Ca(2+)](i) changes.
• Differences in electrical activity patterns (bursting vs. sustained spiking) correlated with distinct [Ca(2+)](i) dynamics.
• [Ca(2+)](i) changes closely followed membrane potential fluctuations in both cell types.
• A computational model successfully replicated islet and beta-cell [Ca(2+)](i) behaviors, suggesting cell heterogeneity underlies observed variations.

Conclusions:

• Electrical activity is the primary driver of [Ca(2+)](i) dynamics in both pancreatic islets and isolated beta-cells.
• Observed differences in [Ca(2+)](i) oscillations stem from distinct electrical activity patterns.
• The validated model provides a framework for understanding beta-cell calcium signaling heterogeneity.