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

H.M. Toland, Karen McCloskey, K.D. Thornbury, N.G. McHale, M.A. Hollywood

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Abstract

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. PMID: 11029279 [PubMed - indexed for MEDLINE]
Original languageEnglish
Pages (from-to)C1327-1335
Number of pages9
JournalAmerican Journal of Physiology - Cell Physiology
Volume279(5)
Publication statusPublished - 2000

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    Toland, H. M., McCloskey, K., Thornbury, K. D., McHale, N. G., & Hollywood, M. A. (2000). Ca(2+)-activated Cl(-) current in sheep lymphatic smooth muscle. American Journal of Physiology - Cell Physiology, 279(5), C1327-1335.