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Journal Article

Regulation of cytosolic free Ca2+ concentration in acinar cells of rat pancreas

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Streb,  Hanspeter
Department of Physiology, Max Planck Institute of Biophysics, Max Planck Society;

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Schulz,  Irene
Department of Physiology, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Streb, H., & Schulz, I. (1983). Regulation of cytosolic free Ca2+ concentration in acinar cells of rat pancreas. American Journal of Physiology-Gastrointestinal and Liver Physiology, 245(3), G347-G357. doi:10.1152/ajpgi.1983.245.3.G347.


Cite as: http://hdl.handle.net/21.11116/0000-0007-F139-9
Abstract
Ca2+ uptake into isolated exocrine pancreatic cells with highly permeable plasma membrane was determined by measuring the decrease in free Ca2+ concentration of the surrounding incubation medium with a Ca2+-specific electrode. In the presence of Mg-ATP and respiratory substrates the free Ca2+ concentration of the incubation medium decreased rapidly after addition of leaky cells until a stable medium free Ca2+ concentration of 4.2 +/- 0.1 X 10-7 mol/l was obtained. Changes in the medium free Ca2+ concentration at steady state by addition of Ca2+ or EGTA were buffered by cellular uptake or release, respectively, until the steady-state free Ca2+ concentration was reestablished. When nonmitochondrial Ca2+ uptake was determined in the presence of a combination of mitochondrial inhibitors (10-5 mol/l antimycin, 5 X 10-6 mol/l oligomycin, and 10-2 mol/l azide), the rate of uptake was considerably reduced, while the steady-state concentration was unaltered. In contrast, mitochondrial uptake that could be observed in the presence of the ATPase inhibitor vanadate (2 X 10-3 mol/l) proceeded at the same rate as the control, but the minimal medium free Ca2+ concentration reached was 2.4 +/- 0.1 X 10-7 mol/l higher than the control. Addition of secretagogues at steady-state free Ca2+ concentration resulted in a Ca2+ release of 0.73 +/- 0.08 nmol/mg protein. The increase in medium free Ca2+ concentration was entirely transient and followed by reuptake to the prestimulation level. The data indicate that a cytosolic free Ca2+ concentration of 4 X 10-7 mol/l can be regulated in pancreatic acinar cells by a nonmitochondrial Mg2+-dependent Ca2+ pool.