Stimulus-secretion coupling and Ca2+ dynamics in pancreatic acinar cells

Area of Science:

• Cellular Biology
• Physiology
• Biochemistry

Background:

• Cytosolic calcium concentration ([Ca2+]c) dynamics are crucial for cellular function.
• Pancreatic acinar cells exhibit specific responses to secretagogues like CCK-8.
• Understanding [Ca2+]c dynamics is key to deciphering cellular signaling pathways.

Purpose of the Study:

• To characterize the unique spatiotemporal dynamics of cytosolic Ca2+ concentration ([Ca2+]c) in various cell types, particularly pancreatic acinar cells.
• To correlate specific [Ca2+]c dynamics with secretory responses and morphological changes induced by CCK-8.
• To explore the interrelationships between secretagogue dose, cellular responses, and signaling molecules like IP3.

Main Methods:

• Characterization of spatiotemporal dynamics in cytosolic Ca2+ concentration ([Ca2+]c).
• Dose-response studies using varying concentrations of cholecystokinin octapeptide (CCK-8).
• Observation and correlation of [Ca2+]c changes with secretory activity and cell morphology.

Main Results:

• Low CCK-8 concentrations (< 10 pM) induce repetitive [Ca2+]c spikes (Ca2+ oscillations).
• Intermediate CCK-8 concentrations (30 pM-1 nM) evoke biphasic [Ca2+]c dynamics (transient peak followed by sustained increase).
• High CCK-8 concentrations (> 1 nM) result in a large transient [Ca2+]c increase followed by steep decay, associated with morphological changes like bleb formation.

Conclusions:

• [Ca2+]c dynamics, including oscillations and biphasic changes, directly correspond to secretory responses in pancreatic acinar cells.
• The dose of secretagogues like CCK-8 dictates the pattern of [Ca2+]c dynamics, influencing both secretion and potential cellular damage.
• Further investigation into the interplay between secretagogue dose, IP3 production, receptor occupation, and morphological changes is warranted.