Regenerative caffeine-induced responses in native rabbit aortic endothelial cells

Area of Science:

• Cellular physiology
• Endothelial cell function
• Calcium signaling

Background:

• Aortic endothelial cells play a crucial role in vascular health.
• Understanding calcium dynamics is key to endothelial cell function.
• Caffeine is known to influence intracellular calcium release.

Purpose of the Study:

• To investigate the nature of calcium release from the endoplasmic reticulum in native rabbit aortic endothelial cells.
• To characterize the relationship between caffeine stimulation, intracellular calcium concentration ([Ca2+]i), and outward membrane currents.
• To determine the role of extracellular calcium in these responses.

Main Methods:

• Patch-clamp technique to measure whole-cell membrane currents in single aortic endothelial cells.
• Fura-2 fluorescence to estimate intracellular calcium concentration ([Ca2+]i).
• Application of caffeine and tetraethylammonium to assess their effects on cellular responses.

Main Results:

• Caffeine (20 mM) evoked outward currents and biphasic intracellular calcium ([Ca2+]i) rises, independent of extracellular calcium.
• Responses to caffeine exhibited an all-or-none pattern.
• Lower caffeine concentrations (0.4-0.5 mM) appeared to deplete intracellular calcium stores.
• Tetraethylammonium blocked spontaneous transient outward currents (STOCs) but only partially reduced caffeine-evoked currents.

Conclusions:

• Calcium release from the endoplasmic reticulum in native aortic endothelial cells occurs in an all-or-none fashion.
• Extracellular calcium is not required for spontaneous or caffeine-induced outward currents.
• Lower caffeine concentrations may deplete intracellular calcium stores, influencing subsequent responses.