Caffeine-evoked, calcium-sensitive membrane currents in rabbit aortic endothelial cells

Area of Science:

• Cardiovascular Physiology
• Cellular Electrophysiology
• Endothelial Cell Biology

Background:

• Endothelial cells play a crucial role in vascular function.
• Caffeine is known to affect intracellular calcium levels.
• Understanding ion channel activity in endothelial cells is vital for cardiovascular health.

Purpose of the Study:

• To investigate the effects of caffeine on intracellular calcium signals and membrane currents in rabbit aortic endothelial cells.
• To elucidate the ionic mechanisms underlying caffeine-evoked currents.
• To determine the role of voltage-sensitive channels and intracellular calcium release.

Main Methods:

• Single-cell photometry using fura-2 for intracellular calcium measurements.
• Whole-cell patch-clamp recording for membrane current analysis.
• Pharmacological manipulation with ryanodine, heparin, tetraethylammonium (TEA), and zinc ions (Zn2+).

Main Results:

• Caffeine induced a transient increase in intracellular calcium, dependent on intracellular stores and inhibited by ryanodine.
• Caffeine evoked a dose- and voltage-dependent outward current.
• This current was partially inhibited by removal of extracellular calcium and significantly reduced by zinc ions, suggesting chloride channel involvement.
• Tetraethylammonium (TEA) partially inhibited the current, indicating a contribution from calcium-activated potassium channels.

Conclusions:

• Caffeine-induced calcium release from intracellular stores correlates with a transient outward current in rabbit aortic endothelial cells.
• The caffeine-sensitive current is mediated by a combination of calcium-activated potassium and chloride conductances.
• These findings highlight the complex interplay of intracellular calcium signaling and ion channel activity in endothelial cell function.