Apical and basolateral Ca(2) channels modulate cytosolic Ca(2)+ in gallbladder epithelia

Area of Science:

• Physiology
• Cell Biology
• Gastroenterology

Background:

• Gallstone formation is linked to altered gallbladder ion transport and increased intracellular calcium.
• Increased cytosolic calcium stimulates gallbladder chloride secretion.
• The mechanism of extracellular calcium entry into gallbladder cells remains unclear.

Purpose of the Study:

• To investigate the hypothesis that extracellular calcium enters the cytosol via apical and basolateral membrane calcium channels.
• To elucidate the role of calcium channels in gallbladder ion transport.

Main Methods:

• Prairie dog gallbladder segments were mounted in Ussing chambers for electrophysiological recordings.
• Unidirectional chloride fluxes were measured using 36Cl with varying mucosal calcium concentrations.
• The effect of lanthanum (a calcium channel blocker) on ion transport was assessed.

Main Results:

• Extracellular calcium positively correlated with short-circuit current and inversely with chloride flux.
• Mucosal lanthanum significantly blunted the effects of extracellular calcium on electrophysiological parameters and chloride flux.
• Basolateral calcium repletion reversed the blocking effects of lanthanum.

Conclusions:

• Extracellular calcium enters gallbladder cells through both apical and basolateral calcium channels.
• Gallbladder apical calcium channels are a potential pathway for biliary calcium entry.
• These channels may play a crucial role in regulating gallbladder ion transport during gallstone formation.