K V2.1 and electrically silent K V channel subunits control excitability and contractility of guinea pig detrusor smooth muscle

Kiril L. Hristov, Muyan Chen, Rupal P. Soder, Shankar P. Parajuli, Qiuping Cheng, Whitney F. Kellett, Georgi Petkov

Research output: Contribution to journalArticle

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Abstract

Voltage-gated K + (K V) channels are implicated in detrusor smooth muscle (DSM) function. However, little is known about the functional role of the heterotetrameric K V channels in DSM. In this report, we provide molecular, electrophysiological, and functional evidence for the presence of K V2.1 and electrically silent K V channel subunits in guinea pig DSM. Stromatoxin-1 (ScTx1), a selective inhibitor of the homotetrameric K V2.1, K V2.2, and K V4.2 as well as the heterotetrameric K V2.1/6.3 and K V2.1/9.3 channels, was used to examine the role of these K V channels in DSM function. RT-PCR indicated mRNA expression of K V2.1, K V6.2- 6.3, K V8.2, and K V9.1-9.3 subunits in isolated DSM cells. K V2.1 protein expression was confirmed by Western blot and immunocytochemistry. Perforated whole cell patchclamp experiments revealed that ScTx1 (100 nM) inhibited the amplitude of the K V current in freshly isolated DSM cells. ScTx1 (100 nM) did not significantly change the steady-state activation and inactivation curves for K V current. However, ScTx1 (100 nM) decreased the activation time-constant of the K V current at positive voltages. Although our patch-clamp data could not exclude the presence of the homotetrameric K V2.1 channels, the biophysical characteristics of the ScTx1-sensitive current were consistent with the presence of heterotetrameric K V2.1/silent K V channels. Currentclamp recordings showed that ScTx1 (100 nM) did not change the DSM cell resting membrane potential. ScTx1 (100 nM) increased the spontaneous phasic contraction amplitude, muscle force, and muscle tone as well as the amplitude of the electrical field stimulationinduced contractions of isolated DSM strips. Collectively, our data revealed that K V2.1-containing channels are important physiological regulators of guinea pig DSM excitability and contractility.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume302
Issue number2
DOIs
StatePublished - Jan 1 2012

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Smooth Muscle
Guinea Pigs
Smooth Muscle Myocytes
Muscle Contraction
Membrane Potentials
Western Blotting
Immunohistochemistry
Cell Membrane
Muscles
Polymerase Chain Reaction
Messenger RNA

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cell Biology

Cite this

K V2.1 and electrically silent K V channel subunits control excitability and contractility of guinea pig detrusor smooth muscle. / Hristov, Kiril L.; Chen, Muyan; Soder, Rupal P.; Parajuli, Shankar P.; Cheng, Qiuping; Kellett, Whitney F.; Petkov, Georgi.

In: American Journal of Physiology - Cell Physiology, Vol. 302, No. 2, 01.01.2012.

Research output: Contribution to journalArticle

Hristov, Kiril L. ; Chen, Muyan ; Soder, Rupal P. ; Parajuli, Shankar P. ; Cheng, Qiuping ; Kellett, Whitney F. ; Petkov, Georgi. / K V2.1 and electrically silent K V channel subunits control excitability and contractility of guinea pig detrusor smooth muscle. In: American Journal of Physiology - Cell Physiology. 2012 ; Vol. 302, No. 2.
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AU - Parajuli, Shankar P.

AU - Cheng, Qiuping

AU - Kellett, Whitney F.

AU - Petkov, Georgi

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AB - Voltage-gated K + (K V) channels are implicated in detrusor smooth muscle (DSM) function. However, little is known about the functional role of the heterotetrameric K V channels in DSM. In this report, we provide molecular, electrophysiological, and functional evidence for the presence of K V2.1 and electrically silent K V channel subunits in guinea pig DSM. Stromatoxin-1 (ScTx1), a selective inhibitor of the homotetrameric K V2.1, K V2.2, and K V4.2 as well as the heterotetrameric K V2.1/6.3 and K V2.1/9.3 channels, was used to examine the role of these K V channels in DSM function. RT-PCR indicated mRNA expression of K V2.1, K V6.2- 6.3, K V8.2, and K V9.1-9.3 subunits in isolated DSM cells. K V2.1 protein expression was confirmed by Western blot and immunocytochemistry. Perforated whole cell patchclamp experiments revealed that ScTx1 (100 nM) inhibited the amplitude of the K V current in freshly isolated DSM cells. ScTx1 (100 nM) did not significantly change the steady-state activation and inactivation curves for K V current. However, ScTx1 (100 nM) decreased the activation time-constant of the K V current at positive voltages. Although our patch-clamp data could not exclude the presence of the homotetrameric K V2.1 channels, the biophysical characteristics of the ScTx1-sensitive current were consistent with the presence of heterotetrameric K V2.1/silent K V channels. Currentclamp recordings showed that ScTx1 (100 nM) did not change the DSM cell resting membrane potential. ScTx1 (100 nM) increased the spontaneous phasic contraction amplitude, muscle force, and muscle tone as well as the amplitude of the electrical field stimulationinduced contractions of isolated DSM strips. Collectively, our data revealed that K V2.1-containing channels are important physiological regulators of guinea pig DSM excitability and contractility.

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