Functional link between muscarinic receptors and large-conductance Ca2+-activated K+ channels in freshly isolated human detrusor smooth muscle cells

Shankar P. Parajuli, Kiril L. Hristov, Qiuping Cheng, John Malysz, Eric S. Rovner, Georgi Petkov

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Activation of muscarinic acetylcholine receptors (mAChRs) constitutes the primary mechanism for enhancing excitability and contractility of human detrusor smooth muscle (DSM). Since the large-conductance Ca2+-activated K+ (KCa1.1) channels are key regulators of human DSM function, we investigated whether mAChR activation increases human DSM excitability by inhibiting KCa1.1 channels. We used the mAChR agonist, carbachol, to determine the changes in KCa1.1 channel activity upon mAChR activation in freshly isolated human DSM cells obtained from open bladder surgeries using the perforated whole cell and single KCa1.1 channel patch-clamp recordings. Human DSM cells were collected from 29 patients (23 males and 6 females, average age of 65.9 ± 1.5 years). Carbachol inhibited the amplitude and frequency of KCa1.1 channel-mediated spontaneous transient outward currents and spontaneous transient hyperpolarizations, which are triggered by the release of Ca2+ from ryanodine receptors. Carbachol also caused membrane potential depolarization, which was not observed in the presence of iberiotoxin, a KCa1.1 channel inhibitor, indicating the critical role of the KCa1.1 channels. The potential direct carbachol effects on KCa1.1 channels were examined under conditions of removing the major cellular Ca2+ sources for KCa1.1 channel activation with pharmacological inhibitors (thapsigargin, ryanodine, and nifedipine). In the presence of these inhibitors, carbachol did not affect the single KCa1.1 channel open probability and mean KCa1.1 channel conductance (cell-attached configuration) or depolarization-induced whole cell steady-state KCa1.1 currents. The data support the concept that mAChR activation triggers indirect functional KCa1.1 channel inhibition mediated by intracellular Ca2+, thus increasing the excitability in human DSM cells.

Original languageEnglish (US)
Pages (from-to)665-675
Number of pages11
JournalPflugers Archiv European Journal of Physiology
Volume467
Issue number4
DOIs
StatePublished - Jan 1 2015

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Calcium-Activated Potassium Channels
Muscarinic Receptors
Carbachol
Smooth Muscle Myocytes
Muscle
Cells
Chemical activation
Smooth Muscle
Depolarization
Ryanodine
Ryanodine Receptor Calcium Release Channel
Thapsigargin
Clamping devices
Nifedipine
Membrane Potentials
Surgery
Urinary Bladder
Pharmacology
Membranes

All Science Journal Classification (ASJC) codes

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

Cite this

Functional link between muscarinic receptors and large-conductance Ca2+-activated K+ channels in freshly isolated human detrusor smooth muscle cells. / Parajuli, Shankar P.; Hristov, Kiril L.; Cheng, Qiuping; Malysz, John; Rovner, Eric S.; Petkov, Georgi.

In: Pflugers Archiv European Journal of Physiology, Vol. 467, No. 4, 01.01.2015, p. 665-675.

Research output: Contribution to journalArticle

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