Ca(2+)-activated Cl(-) current in sheep lymphatic smooth muscle.

Toland, H. M. and McCloskey, K. D. and Thornbury, Keith D. and McHale, Noel G. and Hollywood, Mark A. (2000) Ca(2+)-activated Cl(-) current in sheep lymphatic smooth muscle. Am J Physiol Cell Physiol., 279 (5). pp. 1327-1335.

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Freshly dispersed sheep mesenteric lymphatic smooth muscle cells were studied at 37 degrees C using the perforated patch-clamp technique with Cs(+)- and K(+)-filled pipettes. Depolarizing steps evoked currents that consisted of L-type Ca(2+) [I(Ca(L))] current and a slowly developing current. The slow current reversed at 1 +/- 1.5 mV with symmetrical Cl(-) concentrations compared with 23.2 +/- 1.2 mV (n = 5) and -34.3 +/- 3.5 mV (n = 4) when external Cl(-) was substituted with either glutamate (86 mM) or I(-) (125 mM). Nifedipine (1 microM) blocked and BAY K 8644 enhanced I(Ca(L)), the slow-developing sustained current, and the tail current. The Cl(-) channel blocker anthracene-9-carboxylic acid (9-AC) reduced only the slowly developing inward and tail currents. Application of caffeine (10 mM) to voltage-clamped cells evoked currents that reversed close to the Cl(-) equilibrium potential and were sensitive to 9-AC. Small spontaneous transient depolarizations and larger action potentials were observed in current clamp, and these were blocked by 9-AC. Evoked action potentials were triphasic and had a prominent plateau phase that was selectively blocked by 9-AC. Similarly, fluid output was reduced by 9-AC in doubly cannulated segments of spontaneously pumping sheep lymphatics, suggesting that the Ca(2+)-activated Cl(-) current plays an important role in the electrical activity underlying spontaneous activity in this tissue.

Item Type: Article
Uncontrolled Keywords: 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/pharmacology; Action Potentials/drug effects; Animals; Anthracenes/pharmacology; Calcium/metabolism; Calcium/physiology; Calcium Channel Agonists/pharmacology; Calcium Channel Blockers/pharmacology; Calcium Channels, L-Type/drug effects; Calcium Channels, L-Type/physiology; Chloride Channels/antagonists & inhibitors; Chloride Channels/physiology; Electric Conductivity; Female; Intracellular Membranes/metabolism; Ions; Lymphatic System/cytology; Lymphatic System/drug effects; Lymphatic System/metabolism; Male; Muscle, Smooth/cytology; Muscle, Smooth/drug effects; Muscle, Smooth/metabolism; Nifedipine/pharmacology; Patch-Clamp Techniques; Sheep
Subjects: Science
Research Centres: Smooth Muscle Research Centre
Depositing User: Concepta Woods
Date Deposited: 08 Mar 2012 13:31
Last Modified: 11 Nov 2014 16:10

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