NDLI: Ionic currents in intimal cultured synoviocytes from the rabbit

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Large, R. J. Hollywood, M. A. Sergeant, G. P. Thornbury, K. D. Bourke, S. Levick, J. R. McHale, N. G.
Description	Country affiliation: Ireland Author Affiliation: Large RJ ( Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland.)
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 Ca(2+)-dependent protein kinase C. This study aimed to define synoviocyte membrane currents and channels that may influence synoviocyte Ca(2+) 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 C(s+) pipette solution yielded a transient inward current that disappeared in Ca(2+)-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 -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 Ca(2+) currents. They thus express ion channels regulating membrane Ca(2+) permeability and electrochemical gradient. Since Ca(2+)-dependent kinases are major regulators of synovial hyaluronan secretion, the synoviocyte ion channels are likely to be important in the regulation of hyaluronan secretion.
File Format	HTM / HTML
ISSN	03636143
e-ISSN	15221563
DOI	10.1152/ajpcell.00028.2010
Journal	American Journal of Physiology - Cell Physiology
Issue Number	5
Volume Number	299
Language	English
Publisher	American Physiological Society
Publisher Date	2010-11-01
Publisher Place	United States
Access Restriction	Open
Subject Keyword	Discipline Cell Biology Ion Channels Metabolism Ion Transport Physiology Synovial Membrane Cytology Animals Calcium Channel Blockers Calcium Channels, L-type Cells, Cultured Glucuronosyltransferase Genetics Hyaluronic Acid Membrane Potentials Nifedipine Patch-clamp Techniques Potassium Channel Blockers Potassium Channels Rabbits Shaker Superfamily Of Potassium Channels Research Support, Non-u.s. Gov't
Content Type	Text
Resource Type	Article
Subject	Cell Biology Physiology

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