Effects of the K+ channel blockers paspalitrem-C and paxilline on mammalian smooth muscle

DeFarias, Fernando P.; Carvalho, Márcia; Lee, Seok H.; Kaczorowski, Gregory J.; Suarez‐Kurtz, Guilherme

doi:10.1016/s0014-2999(96)00540-7

Cited by 38 publications

(24 citation statements)

References 17 publications

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“…10, A-C, show that the addition of 10 M paxilline to resting tissues subjected to organ culture for 0, 7, or 9 days increased the frequency and amplitude of spontaneous contractions. This is consistent with previous studies showing that inhibition of BK Ca channels with paxilline increased spontaneous contractions of resting smooth muscle strips (11,17). Our BSM preparation does not typically exhibit spontaneous activity (55,61).…”

Section: Quantification Of Rock-i and Pkg In Organ-cultured Bsm Tissuesupporting

confidence: 93%

“…After the equilibration period, the strips were incubated with the large-conductance calcium-activated potassium channel (BKCa) inhibitor paxilline (10 M) for 5 min. The paxilline concentration was chosen based on data from a previous study (17). After the inhibitor was added to the muscle bath, the frequency and magnitude of spontaneous contractions were recorded using a Grass FT.03 force transducer and AD Laboratory Chart 5 software for Windows.…”

Section: Methodsmentioning

confidence: 99%

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Bladder smooth muscle organ culture preparation maintains the contractile phenotype

Wang

Kendig

Chang

et al. 2012

American Journal of Physiology-Renal Physiology

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Smooth muscle cells, when subjected to culture, modulate from a contractile to a secretory phenotype. This has hampered the use of cell culture for molecular techniques to study the regulation of smooth muscle biology. The goal of this study was to develop a new organ culture model of bladder smooth muscle (BSM) that would maintain the contractile phenotype and aid in the study of BSM biology. Our results showed that strips of BSM subjected to up to 9 days of organ culture maintained their contractile phenotype, including the ability to achieve near-control levels of force with a temporal profile similar to that of noncultured tissues. The technical aspects of our organ culture preparation that were responsible, in part, for the maintenance of the contractile phenotype were a slight longitudinal stretch during culture and subjection of the strips to daily contraction-relaxation. The tissues contained viable cells throughout the cross section of the strips. There was an increase in extracellular collagenous matrix, resulting in a leftward shift in the passive length-tension relationship. There were no significant changes in the content of smooth muscle-specific α-actin, calponin, h-caldesmon, total myosin heavy chain, protein kinase G, Rho kinase-I, or the ratio of SM1 to SM2 myosin isoforms. Moreover the organ cultured tissues maintained functional voltage-gated calcium channels and large-conductance calcium-activated potassium channels. Therefore, we propose that this novel BSM organ culture model maintains the contractile phenotype and will be a valuable tool for the use in cellular/molecular biology studies of bladder myocytes.

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Section: Quantification Of Rock-i and Pkg In Organ-cultured Bsm Tissuesupporting

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Bladder smooth muscle organ culture preparation maintains the contractile phenotype

Wang

Kendig

Chang

et al. 2012

American Journal of Physiology-Renal Physiology

View full text Add to dashboard Cite

show abstract

“…2). In UBSM isolated from various species and humans, pharmacological inhibition of BK channels increases the amplitude, duration, and force of the spontaneous phasic contractions, as well as UBSM tone (21,35,37,51,56,58,60,61,65,109,119,134,152,153,155). In contrast, iberiotoxin had no effect on phasic and tonic contractions of UBSM strips isolated from mice that lacked the BK channel pore-forming ␣-subunit (21), which further confirmed the selectivity of iberiotoxin for UBSM BK channels.…”

Section: Ubsm Bk Channel Physiology and Pharmacologymentioning

confidence: 57%

Central role of the BK channel in urinary bladder smooth muscle physiology and pathophysiology

Petkov

2014

American Journal of Physiology-Regulatory, Integrative and Comp

133

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The physiological functions of the urinary bladder are to store and periodically expel urine. These tasks are facilitated by the contraction and relaxation of the urinary bladder smooth muscle (UBSM), also known as detrusor smooth muscle, which comprises the bladder wall. The large-conductance voltage- and Ca(2+)-activated K(+) (BK, BKCa, MaxiK, Slo1, or KCa1.1) channel is highly expressed in UBSM and is arguably the most important physiologically relevant K(+) channel that regulates UBSM function. Its significance arises from the fact that the BK channel is the only K(+) channel that is activated by increases in both voltage and intracellular Ca(2+). The BK channels control UBSM excitability and contractility by maintaining the resting membrane potential and shaping the repolarization phase of the spontaneous action potentials that determine UBSM spontaneous rhythmic contractility. In UBSM, these channels have complex regulatory mechanisms involving integrated intracellular Ca(2+) signals, protein kinases, phosphodiesterases, and close functional interactions with muscarinic and β-adrenergic receptors. BK channel dysfunction is implicated in some forms of bladder pathologies, such as detrusor overactivity, and related overactive bladder. This review article summarizes the current state of knowledge of the functional role of UBSM BK channels under normal and pathophysiological conditions and provides new insight toward the BK channels as targets for pharmacological or genetic control of UBSM function. Modulation of UBSM BK channels can occur by directly or indirectly targeting their regulatory mechanisms, which has the potential to provide novel therapeutic approaches for bladder dysfunction, such as overactive bladder and detrusor underactivity.

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“…Pharmacological inhibition of the BK channel with selective blockers, including peptides, such as iberiotoxin, or small molecules, such as paxilline, significantly increases DSM contractions (9,11,41). Enhancement of DSM contractility is a result of membrane depolarization, activation of Ca V channels, and increase in global intracellular Ca 2ϩ levels.…”

Section: Discussionmentioning

confidence: 99%

Large-conductance voltage- and Ca²⁺-activated K⁺ channel regulation by protein kinase C in guinea pig urinary bladder smooth muscle

Hristov

Smith

Parajuli

et al. 2014

American Journal of Physiology-Cell Physiology

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Large-conductance voltage- and Ca(2+)-activated K(+) (BK) channels are critical regulators of detrusor smooth muscle (DSM) excitability and contractility. PKC modulates the contraction of DSM and BK channel activity in non-DSM cells; however, the cellular mechanism regulating the PKC-BK channel interaction in DSM remains unknown. We provide a novel mechanistic insight into BK channel regulation by PKC in DSM. We used patch-clamp electrophysiology, live-cell Ca(2+) imaging, and functional studies of DSM contractility to elucidate BK channel regulation by PKC at cellular and tissue levels. Voltage-clamp experiments showed that pharmacological activation of PKC with PMA inhibited the spontaneous transient BK currents in native freshly isolated guinea pig DSM cells. Current-clamp recordings revealed that PMA significantly depolarized DSM membrane potential and inhibited the spontaneous transient hyperpolarizations in DSM cells. The PMA inhibitory effects on DSM membrane potential were completely abolished by the selective BK channel inhibitor paxilline. Activation of PKC with PMA did not affect the amplitude of the voltage-step-induced whole cell steady-state BK current or the single BK channel open probability (recorded in cell-attached mode) upon inhibition of all major Ca(2+) sources for BK channel activation with thapsigargin, ryanodine, and nifedipine. PKC activation with PMA elevated intracellular Ca(2+) levels in DSM cells and increased spontaneous phasic and nerve-evoked contractions of DSM isolated strips. Our results support the concept that PKC activation leads to a reduction of BK channel activity in DSM via a Ca(2+)-dependent mechanism, thus increasing DSM contractility.

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Effects of the K+ channel blockers paspalitrem-C and paxilline on mammalian smooth muscle

Cited by 38 publications

References 17 publications

Bladder smooth muscle organ culture preparation maintains the contractile phenotype

Bladder smooth muscle organ culture preparation maintains the contractile phenotype

Central role of the BK channel in urinary bladder smooth muscle physiology and pathophysiology

Large-conductance voltage- and Ca²⁺-activated K⁺ channel regulation by protein kinase C in guinea pig urinary bladder smooth muscle

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Effects of the K+ channel blockers paspalitrem-C and paxilline on mammalian smooth muscle

Cited by 38 publications

References 17 publications

Bladder smooth muscle organ culture preparation maintains the contractile phenotype

Bladder smooth muscle organ culture preparation maintains the contractile phenotype

Central role of the BK channel in urinary bladder smooth muscle physiology and pathophysiology

Large-conductance voltage- and Ca2+-activated K+ channel regulation by protein kinase C in guinea pig urinary bladder smooth muscle

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Product

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Large-conductance voltage- and Ca²⁺-activated K⁺ channel regulation by protein kinase C in guinea pig urinary bladder smooth muscle