Type

Journal Article

Authors

Noel G McHale
J.R. Levick
S. Bourke
Keith D. Thornbury
Gerard P Sergeant
Mark A Hollywood
Roddy J. Large

Subjects

Biochemistry

Topics
science kinetics protein kinase c cultured membrane potential ion channels 4 aminopyridine synovial fluid

Ionic currents in intimal cultured synoviocytes from the rabbit (2010)

Abstract Hyaluronan, a joint lubricant and regulator of synovial fluid content, is secreted by fibroblast-like synoviocytes lining the joint cavity, and secretion is greatly stimulated by Ca2+-dependent protein kinase C. This study aimed to define synoviocyte membrane currents and channels that may influence synoviocyte Ca2+ dynamics. Resting membrane potential ranged from −30 mV to −66 mV (mean −45 ± 8.60 mV, n = 40). Input resistance ranged from 0.54 GΩ to 2.6 GΩ (mean 1.28 ± 0.57 GΩ; ν = 33). Cell capacitance averaged 97.97 ± 5.93 pF. Voltage clamp using Cs+ pipette solution yielded a transient inward current that disappeared in Ca2+-free solutions and was blocked by 1 μM nifedipine, indicating an L-type calcium current. The current was increased fourfold by the calcium channel activator FPL 64176 (300 nM). Using K+ pipette solution, depolarizing steps positive to −40 mV evoked an outward current that showed kinetics and voltage dependence of activation and inactivation typical of the delayed rectifier potassium current. This was blocked by the nonspecific delayed rectifier blocker 4-aminopyridine. The synoviocytes expressed mRNA for four Kv1 subtypes (Kv1.1, Kv1.4, Kv1.5, and Kv1.6). Correolide (1 μM), margatoxin (100 nM), and α-dendrotoxin block these Kv1 subtypes, and all of these drugs significantly reduced synoviocyte outward current. The current was blocked most effectively by 50 nM κ-dendrotoxin, which is specific for channels containing a Kv1.1 subunit, indicating that Kv1.1 is critical, either as a homomultimeric channel or as a component of a heteromultimeric Kv1 channel. When 50 nM κ-dendrotoxin was added to current-clamped synoviocytes, the cells depolarized by >20 mV and this was accompanied by an increase in intracellular calcium concentration. Similarly, depolarization of the cells with high external potassium solution caused an increase in intracellular calcium, and this effect was greatly reduced by 1 μM nifedipine. In conclusion, fibroblast-like synoviocytes cultured from the inner synovium of the rabbit exhibit voltage-dependent inward and outward currents, including Ca2+ currents. They thus express ion channels regulating membrane Ca2+ permeability and electrochemical gradient. Since Ca2+-dependent kinases are major regulators of synovial hyaluronan secretion, the synoviocyte ion channels are likely to be important in the regulation of hyaluronan secretion.
Collections Ireland -> Dundalk IT -> Subject = Science
Ireland -> Dundalk IT -> Open Access DRIVERset
Ireland -> Dundalk IT -> Status = Published
Ireland -> Dundalk IT -> Type = Article

Full list of authors on original publication

Noel G McHale, J.R. Levick, S. Bourke, Keith D. Thornbury, Gerard P Sergeant, Mark A Hollywood, Roddy J. Large

Experts in our system

1
Noel G McHale
Dundalk IT
Total Publications: 35
 
2
Keith D. Thornbury
Dundalk IT
Total Publications: 27
 
3
Gerard P Sergeant
Dundalk IT
Total Publications: 24
 
4
Mark A Hollywood
Dundalk IT
Total Publications: 35
 
5
Roddy J. Large
Royal College of Surgeons in Ireland
Total Publications: 4