IK channels are involved in the regulatory volume decrease in human epithelial cells.

Area of Science:

• Cell Physiology
• Ion Channel Function
• Epithelial Biology

Background:

• Regulatory volume decrease (RVD) involves KCl efflux mediated by ion channels.
• Previous studies implicated Ca(2+)-dependent K(+) and volume-sensitive Cl(-) channels in RVD.
• The specific type of K(+) channel involved in RVD in human intestinal cells remained unidentified.

Purpose of the Study:

• To identify the specific type of calcium-dependent potassium channel involved in regulatory volume decrease (RVD) in Intestine 407 cells.
• To investigate the role of intermediate conductance (IK), small conductance (SK), and large conductance (BK) potassium channels in this process.

Main Methods:

• RT-PCR was used to assess mRNA expression of different K(+) channel subtypes.
• Electrophysiological techniques, including whole-cell and inside-out patch-clamp recordings, were employed.
• Pharmacological agents (clotrimazole, charybdotoxin, apamin, iberiotoxin) were used to block specific K(+) channels.

Main Results:

• RT-PCR confirmed the expression of IK channel mRNA, but not SK1 or BK channel mRNA.
• Ionomycin and hypotonic stress activated K(+) currents sensitive to IK channel blockers (clotrimazole, charybdotoxin).
• Single-channel recordings identified a CLT-sensitive K(+) channel with intermediate conductance, activated by Ca(2+) and hypotonicity. RVD was inhibited by CLT.

Conclusions:

• The intermediate conductance potassium (IK) channel is expressed in Intestine 407 cells.
• The IK channel is activated by intracellular calcium and hypotonic stress.
• The IK channel plays a significant role in mediating KCl efflux during regulatory volume decrease (RVD) in human intestinal epithelial cells.