Calcium transport by permeabilised rabbit small intestinal epithelial cells

Area of Science:

• Cell Biology
• Gastroenterology
• Physiology

Background:

• Intracellular calcium (Ca2+) is crucial for cellular functions.
• Understanding Ca2+ buffering mechanisms in intestinal epithelial cells is vital.

Purpose of the Study:

• To investigate the role of intracellular structures in Ca2+ buffering by permeabilized rabbit enterocytes.
• To determine the dependence of Ca2+ buffering on cellular components and conditions.

Main Methods:

• Isolation of intestinal epithelial cells from rabbit small intestine.
• Rendering plasma membranes highly permeable to study intracellular processes.
• Monitoring free Ca2+ concentrations using a selective electrode.
• Utilizing radioactive calcium to measure uptake rates.
• Employing mitochondrial inhibitors (azide, oligomycin) and ionophores (A23187).

Main Results:

• Permeabilized enterocytes independently buffered Ca2+ to a basal level of 3.6 x 10(-7) M.
• Ca2+ buffering was dependent on Mg2+ and ATP, and inhibited by A23187.
• Mitochondrial inhibitors and ruthenium red affected the rate but not the final level of Ca2+ buffering.
• Vanadate abolished buffering, while mitochondrial inhibitors blocked it completely.
• Mitochondrial Ca2+ uptake is significant at high concentrations, but non-mitochondrial buffering dominates at physiological levels.
• Crypt cells buffered Ca2+ similarly to villus cells, but at a lower level.

Conclusions:

• Intestinal epithelial cells possess robust Ca2+ buffering capacity.
• Both mitochondrial and non-mitochondrial intracellular compartments contribute to Ca2+ homeostasis.
• Non-mitochondrial buffering is predominant at physiological Ca2+ concentrations.