Eicosanoids modulate apical Ca(2+)-dependent K+ channels in cultured rabbit principal cells

Area of Science:

• Nephrology
• Cell Physiology
• Molecular Biology

Background:

• Maxi K channels are crucial for regulating ion transport in the kidney's principal cells.
• Phospholipase A2 (PLA2) metabolites are signaling molecules involved in various cellular processes.

Purpose of the Study:

• To investigate the effect of apical PLA2 metabolites on maxi K channels in rabbit cortical collecting tubule (CCT) principal cells.
• To determine the role of these channels and metabolites in principal cell volume regulation.

Main Methods:

• Patch clamp technology was used to measure single-channel activity of maxi K channels.
• Primary cultures of rabbit CCT principal cells were utilized.
• Apical application of PLA2 agonists (melittin, arachidonic acid, prostaglandin E2) and antagonists (quinacrine) was performed.
• Changes in cell volume and channel activity were monitored under different tonicity and calcium conditions.

Main Results:

• Apical application of melittin, arachidonic acid, and prostaglandin E2 significantly increased maxi K channel open probability (Po).
• Prostaglandin F2 alpha did not affect channel activity, while quinacrine decreased it.
• Reduced basolateral bath tonicity induced an initial rapid increase in channel activity (NPo), followed by a delayed phase.
• The initial swelling-induced channel activation was abolished by quinacrine, indomethacin, and thapsigargin, suggesting a role for PLA2 metabolites and intracellular calcium stores.

Conclusions:

• Apical PLA2 metabolites modulate maxi K channel activity in CCT principal cells.
• Maxi K channels and eicosanoids are involved in the rapid response of principal cells to osmotic stress.
• The initial phase of swelling-induced channel activation is dependent on PLA2 activity and intracellular calcium, but not extracellular calcium.