Characterization of outward K(+) currents in isolated smooth muscle cells from sheep urethra.

Hollywood, Mark A. and McCloskey, K. D. and McHale, Noel G. and Thornbury, Keith D. (2000) Characterization of outward K(+) currents in isolated smooth muscle cells from sheep urethra. Am J Physiol Cell Physiol. , 279 (2). pp. 420-428.

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Abstract

The perforated-patch technique was used to measure membrane currents in smooth muscle cells from sheep urethra. Depolarizing pulses evoked large transient outward currents and several components of sustained current. The transient current and a component of sustained current were blocked by iberiotoxin, penitrem A, and nifedipine but were unaffected by apamin or 4-aminopyridine, suggesting that they were mediated by large-conductance Ca(2+)-activated K(+) (BK) channels. When the BK current was blocked by exposure to penitrem A (100 nM) and Ca(2+)-free bath solution, there remained a voltage-sensitive K(+) current that was moderately sensitive to blockade with tetraethylammonium (TEA; half-maximal effective dose = 3.0 +/- 0.8 mM) but not 4-aminopyridine. Penitrem A (100 nM) increased the spike amplitude and plateau potential in slow waves evoked in single cells, whereas addition of TEA (10 mM) further increased the plateau potential and duration. In conclusion, both Ca(2+)-activated and voltage-dependent K(+) currents were found in urethral myocytes. Both of these currents are capable of contributing to the slow wave in these cells, suggesting that they are likely to influence urethral tone under certain conditions.

Item Type:	Article
Uncontrolled Keywords:	Animals; Calcium/pharmacology; Female; Male; Membrane Potentials/drug effects; Membrane Potentials/physiology; Muscle, Smooth/drug effects; Muscle, Smooth/physiology; Mycotoxins/pharmacology; Potassium Channels/drug effects; Potassium Channels/physiology; Sheep; Tetraethylammonium/pharmacology; Urethra/drug effects; Urethra/physiology
Subjects:	Science
Research Centres:	Smooth Muscle Research Centre
Depositing User:	Concepta Woods
Date Deposited:	08 Mar 2012 15:56
Last Modified:	11 Nov 2014 16:10
URI:	https://eprints.dkit.ie/id/eprint/204

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