Direct modulation of tracheal Cl−-channel activity by 5,6- and 11,12-EET

1998 ◽  
Vol 275 (3) ◽  
pp. L432-L441 ◽  
Author(s):  
Dany Salvail ◽  
Marc Dumoulin ◽  
Eric Rousseau
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Airway Smooth Muscle ◽  
Current Amplitude ◽  
Resting Membrane Potential ◽  
Channel Activity ◽  
Epoxyeicosatrienoic Acid ◽  
Open Probability ◽  
Direct Modulation ◽  
Cl Channel

Using microelectrode potential measurements, we tested the involvement of Cl− conductances in the hyperpolarization induced by 5,6- and 11,12-epoxyeicosatrienoic acid (EET) in airway smooth muscle (ASM) cells. 5,6-EET and 11,12-EET (0.75 μM) caused −5.4 ± 1.1- and −3.34 ± 0.95-mV hyperpolarizations, respectively, of rabbit tracheal cells (from a resting membrane potential of −53.25 ± 0.44 mV), with significant residual repolarizations remaining after the Ca2+-activated K+ channels had been blocked by 10 nM iberiotoxin. In bilayer reconstitution experiments, we demonstrated that the EETs directly inhibit a Ca2+-insensitive Cl− channel from bovine ASM; 1 μM 5,6-EET and 1.5 μM 11,12-EET lowered the unitary current amplitude by 40 ( n = 6 experiments) and 44.7% ( n = 4 experiments), respectively. Concentration-dependent decreases in channel open probability were observed, with estimated IC50 values of 0.26 μM for 5,6- and 1.15 μM for 11,12-EET. Furthermore, pharmacomechanical tension measurements showed that both regioisomers induced significant bronchorelaxations in epithelium-denuded ASM strips. These results suggest that 5,6- and 11,12-EET can act in ASM as epithelium-derived hyperpolarizing factors.

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

2014 ◽  
Vol 306 (5) ◽  
pp. C460-C470 ◽  
Author(s):  
Kiril L. Hristov ◽  
Amy C. Smith ◽  
Shankar P. Parajuli ◽  
John Malysz ◽  
Georgi V. Petkov
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Guinea Pig ◽  
Bk Channels ◽  
Bk Channel ◽  
K Channel ◽  
Channel Activity ◽  
Open Probability ◽  
Channel Regulation ◽  
Pkc Activation

Large-conductance voltage- and Ca2+-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 Ca2+ 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 Ca2+ sources for BK channel activation with thapsigargin, ryanodine, and nifedipine. PKC activation with PMA elevated intracellular Ca2+ 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 Ca2+-dependent mechanism, thus increasing DSM contractility.

Contraction and depolarization induced by fetal bovine serum in airway smooth muscle

1994 ◽  
Vol 266 (5) ◽  
pp. L528-L535 ◽  
Author(s):  
N. A. Abdullah ◽  
M. Hirata ◽  
K. Matsumoto ◽  
H. Aizawa ◽  
R. Inoue ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Airway Smooth Muscle ◽  
Bovine Serum ◽  
Fetal Bovine Serum ◽  
Muscle Tone ◽  
Smooth Muscles ◽  
Resting Membrane Potential ◽  
Fetal Bovine ◽  
Sustained Increase

We investigated the effects of fetal bovine serum (FBS) on the resting membrane potential and muscle tone of canine airway smooth muscles using tension recording and microelectrode methods. At concentrations < 0.1%, FBS induced a sustained increase in muscle tone. At concentrations < 1%, FBS depolarized the resting membrane potential of dog trachea in a dose-dependent manner. When FBS was dialyzed, it failed to induce a sustained increase in muscle tone or to depolarize the membrane, indicating that FBS contained factor(s) that induced contraction of dog airway smooth muscles. When FBS was dialyzed against distilled water, the outer solution which was freeze dried and then reconstituted (< 1% in original vol) induced a sustained increase in muscle tone, indicating that FBS contained dialyzable factor(s) that increased muscle tone and depolarized the resting membrane potential of dog airway smooth muscles. Methysergide (10(-6) M) or cyproheptadine (10(-6) M), nonspecific antagonists to serotonin receptors, 5-hydroxytryptamines (5-HT1 and 5-HT2), markedly reduced the FBS-induced increase in the muscle tone to approximately 20% of the original value but did not abolish the response. On the other hand, methysergide (10(-6) M) completely suppressed the increase in the muscle tone evoked by peak fractions obtained by application of the dialysate of FBS or 5-HT to a C18 reverse-phase column, indicating the peak fractions contained only 5-HT. These observations indicate that FBS contained 5-HT and an unknown factor(s) responsible for increase in the muscle tone of the airway smooth muscle induced by FBS.

Effect of IgG1 and its fragments on resting membrane potential of isolated tracheal myocytes

1993 ◽  
Vol 74 (4) ◽  
pp. 1948-1953 ◽  
Author(s):  
M. Souhrada ◽  
J. F. Souhrada
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Smooth Muscle Cells ◽  
Airway Smooth Muscle ◽  
Muscle Cells ◽  
Immune Serum ◽  
Resting Membrane Potential ◽  
Airway Smooth Muscle Cells ◽  
Type I ◽  
Trypan Blue Exclusion

We enzymatically isolated airway smooth muscle cells from the trachea of guinea pigs (400–600 g body wt). After removal of connective tissue, strips of trachealis muscle were cleaned under a dissecting microscope and incubated with collagenase (type I, 1 mg/ml) and elastase (type I, 15 U/ml) for 20 min. Cells were resuspended in Dulbecco's modified Eagle's medium and seeded on 1.5% gelatin-coated Petri dishes (35 mm). The viability of cells was assessed by trypan blue exclusion. Individual myocytes were impaled with glass microelectrodes (input resistance 90–100 M omega). Resting membrane potential (Em) was determined before and after administration of 1) immune serum, 2) highly purified specific immunoglobulin G1 (IgG1), and 3) enzymatically prepared fragments of IgG1-F(ab')2 and Fc. We found that 1) Em of isolated tracheal myocytes is -60.5 +/- 0.5 mV; 2) some myocytes exhibit spontaneous electrical rhythm with mean frequency of 16.9 +/- 12 min-1 and mean amplitude of 3.7 +/- 0.6 mV; 3) immune serum, IgG1, and Fc fragments induced a biphasic change in Em: the initial mean depolarization (-51.5 +/- 0.8 mV) was followed by a steady-state hyperpolarization (-68.3 +/- 0.6 mV); and 4) pretreatment of myocytes with amiloride (10(-5) M) or exposure of myocytes to a low-sodium environment prevented changes in Em induced by the passive in vitro sensitization. It is likely that airway smooth muscle cells have a low-affinity Fc receptor, the occupancy of which leads to activation of amiloride-sensitive sodium influx.

Respiratory epithelium-dependent inhibition of protein kinase C of airway smooth muscle cells

1991 ◽  
Vol 70 (5) ◽  
pp. 2137-2144 ◽  
Author(s):  
M. Souhrada ◽  
J. F. Souhrada
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Membrane Potential ◽  
Protein Kinase ◽  
Airway Smooth Muscle ◽  
Isometric Force ◽  
Respiratory Epithelium ◽  
Resting Membrane Potential ◽  
Induced Response ◽  
Kinase C

We have examined the effect of phorbol myristate acetate (PMA) on airway smooth muscle (ASM) in the presence and absence of respiratory epithelium (RE) and analyzed the dependence of this response on extracellular sodium, Na+/H+ exchange, calcium, and cyclooxygenase products; we determined both the resting membrane potential and isometric force developed by ASM preparations. Removal of RE had no effect on the values of the resting membrane potential of ASM cells. In the presence of RE in the preparation, both electrical and contractile responses to PMA (10(-5) M) were significantly different compared with the response of ASM to PMA without RE. When the RE was present, stimulation of protein kinase C caused only a biphasic response in both membrane potential and isometric force. In either the presence or absence of RE, amiloride (10(-5) M) and a low-sodium solution inhibited both electrical and contractile changes of ASM cells caused by PMA. In the presence or absence of RE, verapamil (10(-5) M) attenuated (P less than 0.05) both electrical and contractile responses of ASM cells as induced by PMA. Verapamil, however, had no effect on the last phase of PMA-induced response. Pretreatment of preparations with indomethacin (10(-6) M) changed the PMA-induced response of ASM with RE to a response usually observed in ASM without RE. Finally, the incubation of tracheal preparations without RE with prostaglandin E2 (10(-8) M) altered the response of these preparations in such a way that their electrical and contractile response to PMA was essentially identical to the PMA response observed in preparations with an intact RE.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental differences in Ca2+-activated K+ channel activity in ovine basilar artery

2003 ◽  
Vol 285 (2) ◽  
pp. H701-H709 ◽  
Author(s):  
Mike T. Lin ◽  
David A. Hessinger ◽  
William J. Pearce ◽  
Lawrence D. Longo
Keyword(s):  
Membrane Potential ◽  
Cerebral Arteries ◽  
Outward Current ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Channel Activity ◽  
Open Probability ◽  
Fetal Sheep ◽  
Voltage Gated ◽  
Maximal Activation

A primary determinant of vascular smooth muscle (VSM) tone and contractility is the resting membrane potential, which, in turn, is influenced heavily by K+ channel activity. Previous studies from our laboratory and others have demonstrated differences in the contractility of cerebral arteries from near-term fetal and adult animals. To test the hypothesis that these contractility differences result from maturational changes in voltage-gated K+ channel function, we compared this function in VSM myocytes from adult and fetal sheep cerebral arteries. The primary current-carrying, voltage-gated K+ channels in VSM myocytes are the large conductance Ca2+-activated K+ channels (BKCa) and voltage-activated K+ (KV) channels. We observed that at voltage-clamped membrane potentials of +60 mV in perforated whole cell studies, the normalized outward current densities in fetal myocytes were >30% higher than in those of the adult ( P < 0.05) and that these were predominately due to iberiotoxin-sensitive currents from BKCa channels. Excised, insideout membrane patches revealed nearly identical unitary conductances and Hill coefficients for BKCa channels. The plot of log intracellular [Ca2+] ([Ca2+]i) versus voltage for half-maximal activation ( V½) yielded linear and parallel relationships, and the change in V½ for a 10-fold change in [Ca2+] was also similar. Channel activity increased e-fold for a 19 ± 2-mV depolarization for adult myocytes and for an 18 ± 1-mV depolarization for fetal myocytes ( P > 0.05). However, the relationship between BKCa open probability and membrane potential had a relative leftward shift for the fetal compared with adult myocytes at different [Ca2+]i. The [Ca2+] for half-maximal activation (i.e., the calcium set points) at 0 mV were 8.8 and 4.7 μM for adult and fetal myocytes, respectively. Thus the increased BKCa current density in fetal myocytes appears to result from a lower calcium set point.

Evidence for a sodium electrogenic pump in airway smooth muscle

1981 ◽  
Vol 51 (2) ◽  
pp. 346-352 ◽  
Author(s):  
M. Souhrada ◽  
J. F. Souhrada ◽  
R. M. Cherniack
Keyword(s):  
Smooth Muscle ◽  
High Temperature ◽  
Membrane Potential ◽  
Guinea Pig ◽  
Airway Smooth Muscle ◽  
Specific Inhibitor ◽  
Resting Membrane Potential ◽  
Physiological Salt Solution ◽  
Electrogenic Pump ◽  
Free Solution

We tested the hypothesis that the resting membrane potential (Em) of guinea pig and bovine airway smooth muscle (ASM) (m. trachealis transversus) might be influenced by a Na+ electrogenic pump. To determine the Em of ASM, glass microelectrodes filled with 3 M KCI and offering an impedance between 40 and 80 M omega were used. After incubation a normal oxygenated physiological salt solution (PSS) [pH, 7.38 +/- 0.02 (SD); temp, 37 +/- 0.5 degrees C (SD)] for 60 min, the Em of guinea pig ASM was -62.5 +/- 1.25 (SE) mV (successful impalement of 437 cells of 37 tracheal preparations from 37 different animals) and that of bovine ASM was -60.0 +/- 1.5 mV (successful impalement of 306 cells of 26 tracheal preparations from 26 different animals). Tracheal preparation consisted of 10-mm-long segments of cervical or intrathoracic portions of the trachea. Approximately 30% of the cells of both species exhibited spontaneous electrical activity (slow waves). Studies to determine whether an electrogenic pump was present revealed that a) ouabain (10(-5) M), a specific inhibitor of the Na+ pump, causes depolarization of ASM in both species; b) exposure of ASM to a K+-free solution resulted in a similar depolarization followed by a hyperpolarization; c) exposure to normal PSS after "Na+ loading" resulted in significant hyperpolarization of ASM when these preparations were returned to normal PSS; and d) Em of ASM decreased on exposure to a low temperature (21, 25, and 29 degrees C) and increased at a high temperature (40 degrees C). It is concluded that an active electrogenic pump is present in guinea pig and bovine airway smooth muscle.

U46619, a thromboxane A2 agonist, inhibits KCa channel activity from pig coronary artery

1992 ◽  
Vol 262 (3) ◽  
pp. C708-C713 ◽  
Author(s):  
F. S. Scornik ◽  
L. Toro
Keyword(s):  
Smooth Muscle ◽  
Coronary Artery ◽  
Lipid Bilayers ◽  
Thromboxane A2 ◽  
Inhibitory Effect ◽  
Channel Activity ◽  
Open Probability ◽  
Control Value ◽  
Kca Channels ◽  
Internal Side

Thromboxane A2 (TxA2) is a potent vasoconstrictor derived from the metabolism of arachidonic acid. Because potassium channels are involved in the contraction of vascular smooth muscle, their blockade could contribute to the TxA2-induced contraction. To test this possibility, we studied the effect of the TxA2 stable analogue U46619 on calcium-activated potassium (KCa) channels from coronary artery reconstituted into lipid bilayers. Addition of U46619 (50-150 nM) to the external but not to the internal side of the channel decreased the channel open probability (Po) between 15 and 80% of the control value. The inhibitory effect of U46619 affected both the open and closed states of the channel and could be reversed by internal calcium. Thromboxane B2, the inactive hydrolysis derivative of TxA2, did not affect channel activity. SQ 29548, a TxA2 receptor antagonist, was able to prevent the inhibition by U46619. Furthermore, SQ 29548 added after U46619 could restore channel activity to near control values. These results suggest that TxA2 could be a regulatory factor of KCa channels from coronary smooth muscle and that this regulation could be related to its action as a vasoconstrictor.

Role of HERG-like K+ currents in opossum esophageal circular smooth muscle

1999 ◽  
Vol 277 (6) ◽  
pp. C1284-C1290 ◽  
Author(s):  
Hamid I. Akbarali ◽  
Hemant Thatte ◽  
Xue Dao He ◽  
Wayne R. Giles ◽  
Raj K. Goyal
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Smooth Muscle Cells ◽  
Single Cells ◽  
Circular Muscle ◽  
Muscle Cells ◽  
Resting Membrane Potential ◽  
Channel Blockers ◽  
Circular Smooth Muscle ◽  
Inward Currents

An inwardly rectifying K+ conductance closely resembling the human ether-a-go-go-related gene (HERG) current was identified in single smooth muscle cells of opossum esophageal circular muscle. When cells were voltage clamped at 0 mV, in isotonic K+ solution (140 mM), step hyperpolarizations to −120 mV in 10-mV increments resulted in large inward currents that activated rapidly and then declined slowly (inactivated) during the test pulse in a time- and voltage- dependent fashion. The HERG K+ channel blockers E-4031 (1 μM), cisapride (1 μM), and La3+ (100 μM) strongly inhibited these currents as did millimolar concentrations of Ba2+. Immunoflourescence staining with anti-HERG antibody in single cells resulted in punctate staining at the sarcolemma. At membrane potentials near the resting membrane potential (−50 to −70 mV), this K+ conductance did not inactivate completely. In conventional microelectrode recordings, both E-4031 and cisapride depolarized tissue strips by 10 mV and also induced phasic contractions. In combination, these results provide direct experimental evidence for expression of HERG-like K+ currents in gastrointestinal smooth muscle cells and suggest that HERG plays an important role in modulating the resting membrane potential.

Sign in / Sign up

Export Citation Format

Share Document