What is the mechanism of the calcium influx to pancreatic acinar cells evoked by secretagogues?
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The simple model shown in Fig. 1 can be used to explain pancreatic acinar stimulus-secretion coupling by assuming that the Ca-activated cation channel is not perfectly selective for mono-valent cations, but enables a very slight leak of divalent cations. Stimulation by ACh or CCK releases intracellular Ca (probably from the plasma membrane) raising [Ca++]i. This opens up the 30–35 pS channels giving rise to Na influx and depolarization. At the same time Ca can leak into the cells through the same channels, maintaining an elevated [Ca++]i. Removal of agonist (and/or inclusion of antagonist) causes a rapid reuptake of Ca into the trigger pool (Stolze and Schulz 1980) causing a decrease in [Ca++]i and closure of the channel with rapid return to the resting potential and the resting [Ca++]i.
KeywordsCalcium Plasma Membrane Simple Model Human Physiology Acinar Cell
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