BAY K 8644-induced oscillations in rabbit gall-bladder transepithelial potential difference.

Area of Science:

• Physiology
• Pharmacology
• Cell Biology

Background:

• The rabbit gallbladder is a model for studying epithelial transport.
• Calcium channels play a crucial role in regulating cellular functions, including ion transport.

Purpose of the Study:

• To investigate the effects of the calcium channel activator BAY K 8644 on rabbit gallbladder epithelial transport.
• To determine the impact of BAY K 8644 on transepithelial potential difference, electrical resistance, and sodium fluxes.

Main Methods:

• Experiments were conducted on isolated rabbit gallbladders.
• Transepithelial potential difference (Pd), electrical resistance (Rt), and unidirectional Na+-fluxes were measured.
• The effects of BAY K 8644 at various concentrations were analyzed.
• Nifedipine was used to block calcium channels.

Main Results:

• BAY K 8644 induced regular oscillations in transepithelial Pd (18 mHz, 30-35 microV) without altering mean Pd or Rt.
• Oscillations were primarily elicited from the serosal side.
• A concentration of 10(-5) M BAY K 8644 reduced net Na+ absorption by 16% by inhibiting the mucosa-to-serosa flux.
• Nifedipine blocked the Pd oscillations but did not reverse the Na+ transport inhibition.

Conclusions:

• BAY K 8644 activates calcium channels, leading to increased intracellular calcium concentration.
• This activation results in oscillatory changes in gallbladder potential difference and reduced sodium absorption.
• The findings suggest a role for calcium signaling in regulating gallbladder epithelial transport.