Ionic currents in intimal cultured synoviocytes from the rabbit.

Area of Science:

• Biophysics
• Cell Physiology
• Molecular Biology

Background:

• Hyaluronan, a key joint lubricant, is secreted by fibroblast-like synoviocytes.
• Secretion is regulated by calcium (Ca2+)-dependent protein kinase C.
• Understanding synoviocyte ion channels is vital for regulating Ca2+ dynamics and hyaluronan secretion.

Purpose of the Study:

• To identify and characterize membrane currents and ion channels in fibroblast-like synoviocytes.
• To investigate the role of these channels in regulating intracellular Ca2+ concentration.
• To link ion channel activity to hyaluronan secretion regulation.

Main Methods:

• Electrophysiological recordings (voltage clamp and current clamp) on synoviocytes.
• Pharmacological characterization of ion currents using specific channel blockers and activators.
• Analysis of Kv1 subtype mRNA expression in synoviocytes.
• Measurement of intracellular Ca2+ concentration changes.

Main Results:

• Synoviocytes exhibit voltage-dependent inward (L-type Ca2+) and outward (delayed rectifier K+) currents.
• Kv1.1 potassium channels were identified as critical for outward currents and membrane potential regulation.
• Blockade of Kv1.1 channels led to membrane depolarization and increased intracellular Ca2+.
• L-type Ca2+ currents were confirmed and modulated by activators and blockers.
• Depolarization increased intracellular Ca2+, an effect reduced by nifedipine, highlighting L-type Ca2+ channel involvement.

Conclusions:

• Fibroblast-like synoviocytes possess functional ion channels, including L-type Ca2+ and Kv1.1 K+ channels.
• These channels regulate membrane potential and Ca2+ permeability.
• The identified ion channels are likely integral to the regulation of hyaluronan secretion via Ca2+-dependent pathways.