The endothelium inhibits activation by calcium of vascular neurotransmission

1989 ◽  
Vol 257 (6) ◽  
pp. H1871-H1877
Author(s):  
B. Tesfamariam ◽  
R. M. Weisbrod ◽  
R. A. Cohen
Keyword(s):  
Smooth Muscle ◽  
Electrical Stimulation ◽  
Electrical Field Stimulation ◽  
Bay K 8644 ◽  
Adrenergic Nerves ◽  
Inhibitory Influence ◽  
Free Medium ◽  
Voltage Dependent ◽  
The Difference

The role of calcium in the inhibition by the endothelium of adrenergic neurotransmission was studied in isolated rabbit carotid artery. Contractions induced by transmural electrical field stimulation (0.5-8 Hz), norepinephrine (10(-8)-3 X 10(-5) M), potassium depolarization (15-30 mM), or by readdition of calcium (0.15-2.4 mM) to a calcium-free medium containing potassium (15 mM) were significantly smaller in rings with compared with rings without endothelium. The voltage-dependent calcium channel activator, BAY K 8644 (10(-6) M), increased contractions to all contractile stimuli in rings with more than in rings without endothelium and thereby abolished the inhibitory influence of the endothelium. The inhibition of neurogenic contractions by the endothelium was also, in part, prejunctional, as indicated by decreased overflow of endogenous norepinephrine from superfused segments with compared with segments without endothelium evoked by electrical stimulation (2 Hz) or by reinfusion of calcium (2.5 mM) to calcium-free medium containing potassium (80 mM). BAY K 8644 (10(-6) M) enhanced the overflow of norepinephrine evoked by electrical stimulation or calcium from segments with more than from segments without endothelium and abolished the difference. Thus the endothelium inhibits activation by extracellular calcium of adrenergic nerves and vascular smooth muscle. The action of the endothelium is overcome by BAY K 8644, suggesting that voltage-dependent calcium channels are important in the inhibitory role of the endothelium in both adrenergic nerves and smooth muscle cells.

Contribution of Cav1.2 Ca2+ channels and store-operated Ca2+ entry to pig urethral smooth muscle contraction

2020 ◽  
Vol 318 (2) ◽  
pp. F496-F505
Author(s):  
Benjamin E. Rembetski ◽  
Kenton M. Sanders ◽  
Bernard T. Drumm
Keyword(s):  
Smooth Muscle ◽  
Electrical Field Stimulation ◽  
Smooth Muscle Contraction ◽  
Isometric Tension ◽  
Electrical Field ◽  
Voltage Dependent ◽  
Urethral Smooth Muscle ◽  
Evoked Contractions ◽  
Ca2 Channels

Urethral smooth muscle (USM) generates tone to prevent urine leakage from the bladder during filling. USM tone has been thought to be a voltage-dependent process, relying on Ca2+ influx via voltage-dependent Ca2+ channels in USM cells, modulated by the activation of Ca2+-activated Cl− channels encoded by Ano1. However, recent findings in the mouse have suggested that USM tone is voltage independent, relying on Ca2+ influx through Orai channels via store-operated Ca2+ entry (SOCE). We explored if this pathway also occurred in the pig using isometric tension recordings of USM tone. Pig USM strips generated myogenic tone, which was nearly abolished by the Cav1.2 channel antagonist nifedipine and the ATP-dependent K+ channel agonist pinacidil. Pig USM tone was reduced by the Orai channel blocker GSK-7975A. Electrical field stimulation (EFS) led to phentolamine-sensitive contractions of USM strips. Contractions of pig USM were also induced by phenylephrine. Phenylephrine-evoked and EFS-evoked contractions of pig USM were reduced by ~50–75% by nifedipine and ~30% by GSK-7975A. Inhibition of Ano1 channels had no effect on tone or EFS-evoked contractions of pig USM. In conclusion, unlike the mouse, pig USM exhibited voltage-dependent tone and agonist/EFS-evoked contractions. Whereas SOCE plays a role in generating tone and agonist/neural-evoked contractions in both species, this dominates in the mouse. Tone and agonist/EFS-evoked contractions of pig USM are the result of Ca2+ influx primarily through Cav1.2 channels, and no evidence was found supporting a role of Ano1 channels in modulating these mechanisms.

scholarly journals Knockout of Na+/Ca2+ exchanger in smooth muscle attenuates vasoconstriction and L-type Ca2+ channel current and lowers blood pressure

2010 ◽  
Vol 298 (5) ◽  
pp. H1472-H1483 ◽  
Author(s):  
Jin Zhang ◽  
Chongyu Ren ◽  
Ling Chen ◽  
Manuel F. Navedo ◽  
Laura K. Antos ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Smooth Muscle ◽  
Physiological Role ◽  
Bay K 8644 ◽  
Mesenteric Arteries ◽  
Channel Current ◽  
Dependent Inactivation ◽  
Voltage Dependent ◽  
The Difference ◽  
And Control

Mice with smooth muscle (SM)-specific knockout of Na+/Ca2+ exchanger type-1 (NCX1SM−/−) and the NCX inhibitor, SEA0400, were used to study the physiological role of NCX1 in mouse mesenteric arteries. NCX1 protein expression was greatly reduced in arteries from NCX1SM−/− mice generated with Cre recombinase. Mean blood pressure (BP) was 6–10 mmHg lower in NCX1SM−/− mice than in wild-type (WT) controls. Vasoconstriction was studied in isolated, pressurized mesenteric small arteries from WT and NCX1SM−/− mice and in heterozygotes with a global null mutation (NCX1Fx/−). Reduced NCX1 activity was manifested by a marked attenuation of responses to low extracellular Na+ concentration, nanomolar ouabain, and SEA0400. Myogenic tone (MT, 70 mmHg) was reduced by ∼15% in NCX1SM−/− arteries and, to a similar extent, by SEA0400 in WT arteries. MT was normal in arteries from NCX1Fx/− mice, which had normal BP. Vasoconstrictions to phenylephrine and elevated extracellular K+ concentration were significantly reduced in NCX1SM−/− arteries. Because a high extracellular K+ concentration-induced vasoconstriction involves the activation of L-type voltage-gated Ca2+ channels (LVGCs), we measured LVGC-mediated currents and Ca2+ sparklets in isolated mesenteric artery myocytes. Both the currents and the sparklets were significantly reduced in NCX1SM−/− (vs. WT or NCX1Fx/−) myocytes, but the voltage-dependent inactivation of LVGCs was not augmented. An acute application of SEA0400 in WT myocytes had no effect on LVGC current. The LVGC agonist, Bay K 8644, eliminated the differences in LVGC currents and Ca2+ sparklets between NCX1SM−/− and control myocytes, suggesting that LVGC expression was normal in NCX1SM−/− myocytes. Bay K 8644 did not, however, eliminate the difference in myogenic constriction between WT and NCX1SM−/− arteries. We conclude that, under physiological conditions, NCX1-mediated Ca2+ entry contributes significantly to the maintenance of MT. In NCX1SM−/− mouse artery myocytes, the reduced Ca2+ entry via NCX1 may lower cytosolic Ca2+ concentration and thereby reduce MT and BP. The reduced LVGC activity may be the consequence of a low cytosolic Ca2+ concentration.

Inhibition of dihydropyridine-sensitive calcium entry in hypoxic relaxation of airway smooth muscle

1995 ◽  
Vol 268 (2) ◽  
pp. L201-L206 ◽  
Author(s):  
C. Vannier ◽  
T. L. Croxton ◽  
L. S. Farley ◽  
C. A. Hirshman
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Bay K 8644 ◽  
O2 Concentration ◽  
Voltage Dependent ◽  
Progressive Hypoxia ◽  
Carbamyl Choline

Hypoxia dilates airways in vivo and reduces active tension of airway smooth muscle in vitro. To determine whether hypoxia impairs Ca2+ entry through voltage-dependent channels (VDC), we tested the ability of dihydropyridines to modulate hypoxia-induced relaxation of KCl- and carbamyl choline (carbachol)-contracted porcine bronchi. Carbachol- or KCl-contracted bronchial rings were exposed to progressive hypoxia in the presence or absence of 1 microM BAY K 8644 (an L-type-channel agonist). In separate experiments, rings were contracted with carbachol or KCl, treated with nifedipine (a VDC antagonist), and finally exposed to hypoxia. BAY K 8644 prevented hypoxia-induced relaxation in KCl-contracted bronchi. Nifedipine (10(-5) M) totally relaxed KCl- contracted bronchi. Carbachol-contracted bronchi were only partially relaxed by nifedipine but were completely relaxed when the O2 concentration of the gas was reduced from 95 to 0%. These data indicate that hypoxia can reduce airway smooth muscle tone by limiting entry of Ca2+ through a dihydropyridine-sensitive pathway, but that other mechanisms also contribute to hypoxia-induced relaxation of carbachol-contracted bronchi.

Release of epithelium-derived PGE2 from canine trachea after antigen inhalation

1998 ◽  
Vol 274 (2) ◽  
pp. L220-L225 ◽  
Author(s):  
I. McGrogan ◽  
L. J. Janssen ◽  
J. Wattie ◽  
P. M. O’Byrne ◽  
E. E. Daniel
Keyword(s):  
Smooth Muscle ◽  
Electrical Field Stimulation ◽  
Tracheal Smooth Muscle ◽  
Organ Bath ◽  
Field Stimulation ◽  
Electrical Field ◽  
Concentration Response Curve

To investigate the role of prostaglandin (PG) E2 in allergen-induced hyperresponsiveness, dogs inhaled either the allergen Ascaris suum or vehicle (Sham). Twenty-four hours after inhalation, some animals exposed to allergen demonstrated an increased responsiveness to acetylcholine challenge in vivo (Hyp-Resp), whereas others did not (Non-Resp). Strips of tracheal smooth muscle, either epithelium intact or epithelium denuded, were suspended on stimulating electrodes, and a concentration-response curve to carbachol (10−9 to 10−5 M) was generated. Tissues received electrical field stimulation, and organ bath fluid was collected to determine PGE2content. With the epithelium present, all three groups contracted similarly to 10−5 M carbachol, whereas epithelium-denuded tissues from animals that inhaled allergen contracted more than tissues from Sham dogs. In response to electrical field stimulation, Hyp-Resp tissues contracted less than Sham tissues in the presence of epithelium and more than Sham tissues in the absence of epithelium. PGE2release in the muscle bath was greater in Non-Resp tissues than in Sham or Hyp-Resp tissues when the epithelium was present. Removal of the epithelium greatly inhibited PGE2release. We conclude that tracheal smooth muscle is hyperresponsive in vitro after in vivo allergen exposure only when the modulatory effect of the epithelium, largely through PGE2 release, is removed.

Calcium channel activation in vascular smooth muscle by BAY K 8644

1984 ◽  
Vol 62 (11) ◽  
pp. 1401-1410 ◽  
Author(s):  
C. M. Su ◽  
V. C. Swamy ◽  
D. J. Triggle
Keyword(s):  
Smooth Muscle ◽  
Dose Response ◽  
Response Curve ◽  
Bay K 8644 ◽  
Rat Tail Artery ◽  
Channel Activation ◽  
Tail Artery ◽  
Voltage Dependent ◽  
Adrenoceptor Agonists ◽  
Rat Tail

BAY K 8644 (methyl-1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)pyridine-5-carboxylate) and CGP 28 392 (ethyl-4(2-difluoromethoxyphenyl)-1,4,5,7-tetrahydro-2-methyl-5-oxofuro-[3,4-b]pyridine-3-carboxylate) are closely related in structure to nifedipine and other 1,4-dihydropyridine Ca2+ channel antagonists. However, both BAY K 8644 and CGP 28 392 serve as activators of Ca2+ channels. In the rat tail artery, responses to BAY K 8644 are dependent upon [Formula: see text] and prior stimulation by K+ or by the α-adrenoceptor agonists, phenylephrine and BHT 920 (6-allyl-2-amino-5,6,7,8,-tetrahydro-4H-thiazolo[4,5-d]azepin dihydrochloride). Responses are blocked noncompetitively by the Ca2+ channel antagonists D-600 ((−)-D-600 > (+)-D-600) and diltiazem, but competitively by nifedipine (pA2 = 8.27). This suggests that activator and inhibitor 1,4-dihydropyridines interact at the same site. BAY K 8644 potentiates K+ responses and Ca2+ responses in K+-depolarizing media. The leftward shift of the K+ dose–response curve produced by BAY K 8644 suggests that this ligand facilitates the voltage-dependent activation of the Ca2+ channel. The pA2 value for nifedipine antagonism of BAY K 8644 responses is significantly lower than that for nifedipine antagonism of Ca2+ responses in K+ (25–80 mM) depolarizing media (9.4–9.6), suggesting that the state of the channel may differ according to the activating stimulus.

scholarly journals Attenuation of Canonical Transient Receptor Potential-Like Channel 6 Expression Specifically Reduces the Diacylglycerol-Mediated Increase in Intracellular Calcium in Human Myometrial Cells

Endocrinology ◽  
2010 ◽  
Vol 151 (1) ◽  
pp. 406-416 ◽  
Author(s):  
Daesuk Chung ◽  
Yoon-Sun Kim ◽  
Jennifer N. Phillips ◽  
Aida Ulloa ◽  
Chun-Ying Ku ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Transient Receptor Potential ◽  
Contractile Activity ◽  
Receptor Potential ◽  
Myometrial Cells ◽  
Canonical Transient Receptor Potential ◽  
Voltage Dependent ◽  
Transient Receptor ◽  
Entry Mechanism

Abstract An increase in intracellular Ca2+ ([Ca2+]i) as a result of release of Ca2+ from intracellular stores or influx of extracellular Ca2+ contributes to the regulation of smooth muscle contractile activity. Human uterine smooth muscle cells exhibit receptor-, store-, and diacylglycerol (OAG)-mediated extracellular Ca2+-dependent increases in [Ca2+]i (SRCE) and express canonical transient receptor potential-like channels (TRPC) mRNAs (predominantly TRPC1, -4, and -6) that have been implicated in SRCE. To determine the role of TRPC6 in human myometrial SRCE, short hairpin RNA constructs were designed that effectively targeted a TRPC6 mRNA reporter for degradation. One sequence was used to produce an adenovirus construct (TC6sh1). TC6sh1 reduced TRPC6 mRNA but not TRPC1, -3, -4, -5, or -7 mRNAs in PHM1-41 myometrial cells. Compared with uninfected cells or cells infected with empty vector, the increase in [Ca2+]i in response to OAG was specifically inhibited by TC6sh1, whereas SRCE responses elicited by either oxytocin or thapsigargin were not changed. Similar findings were observed in primary pregnant human myometrial cells. When PHM1-41 cells were activated by OAG in the absence of extracellular Na+, the increase in [Ca2+]i was partially reduced. Furthermore, pretreatment with nifedipine, an L-type calcium channel blocker, also partially reduced the OAG-induced [Ca2+]i increase. Similar effects were observed in primary human myometrial cells. These findings suggest that OAG activates channels containing TRPC6 in myometrial cells and that these channels act via both enhanced Na+ entry coupled to activation of voltage-dependent Ca2+ entry channels and a nifedipine-independent Ca2+ entry mechanism to promote elevation of intracellular Ca2+.

Delayed shortening and shrinkage of cochlear outer hair cells

1992 ◽  
Vol 263 (5) ◽  
pp. C1088-C1095 ◽  
Author(s):  
S. Ohnishi ◽  
M. Hara ◽  
M. Inoue ◽  
T. Yamashita ◽  
T. Kumazawa ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Hair Cells ◽  
Cytochalasin B ◽  
Electrical Field Stimulation ◽  
Outer Hair Cells ◽  
Disulfonic Acid ◽  
Free Medium ◽  
Electrical Field ◽  
Cl Channels ◽  
Stimulation Of

Slow shortening of cochlear outer hair cells has been speculated to modify cochlear sensitivity. Tetanic electrical field stimulation of isolated outer hair cells from guinea pigs shortened the cells for 2-3 min. Electrical stimulation reduced cell length and volume (-13.5 +/- 1.5 and -37.3 +/- 3.0% of initial values, respectively, n = 16) and decreased the intracellular Cl- concentration. Cytochalasin B (100 microM) inhibited electrical stimulation-induced shortening but not volume reduction. The following chemicals or manipulations inhibited the responses: 10 microM furosemide, 0.1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), 1 mM anthracene-9-carboxylic acid (AC9), 25 mM tetraethylammonium, 2.3 microM charybdotoxin (ChTX), 250 nM omega-conotoxin, and Ca(2+)-free medium. These findings suggest that both electrical stimulation-induced shortening and shrinkage of outer hair cells result not only from an actin-mediated contractile force, but also from Cl- efflux through furosemide-, DIDS-, and AC9-sensitive Cl- channels, and K+ efflux through ChTX-sensitive K+ channels.

Differential tachykinin receptor subtype activation in capsaicin and KCl contractions of guinea pig trachealis

1995 ◽  
Vol 269 (6) ◽  
pp. L837-L842
Author(s):  
R. W. Mitchell ◽  
I. M. Ndukwu ◽  
A. Herrnreiter ◽  
K. Uzendoski ◽  
B. Gitter ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Electrical Field Stimulation ◽  
Receptor Subtype ◽  
Nk1 Receptor ◽  
Electrical Field ◽  
Tachykinin Receptor ◽  
Nk1 Receptor Antagonist

We assessed the role of endogenously secreted tachykinins in mediating contraction caused by potassium chloride (KCl) in guinea pig tracheal smooth muscle (TSM) strips in vitro. Maximal isometric contraction was elicited with approximately 45 mM KCl and was 196 +/- 8% of the response to electrical field stimulation (% EFS) in the same tissues. Muscarinic receptor blockade with atropine modestly attenuated this contraction caused by KCl to 175 +/- 9 %EFS (P < 0.05), and treatment with a selective neurokinin subtype 1 (NK1) receptor antagonist, LY-297911, caused even greater inhibition of KCl-elicited contraction to 124 +/- 8 %EFS (P < 0.001). By contrast, SR-48968, a selective NK2 antagonist, had no effect on contraction caused by KCl (183 +/- 9 %EFS; P = NS vs. KCl alone). However, given together at the same concentration, SR-48968 augmented the inhibition of contraction caused by LY-297911 to 93 +/- 15 %EFS (P < 0.05 vs. LY-297911 alone). In contrast to the effect on KCl-induced contraction, LY-297911 caused only moderate inhibition of the contraction caused by capsaicin to 81 +/- 13 %EFS (P < 0.05 vs. control, 114 +/- 15 %EFS), whereas SR-48968 caused substantial attenuation of contraction caused by capsaicin to 23 +/- 5 %EFS (P < 0.005 vs. LY-297911). We demonstrate that a significant portion of the contraction caused by KCl, in addition to capsaicin, is elicited in guinea pig TSM through neurokinin secretion. However, NK1 receptors predominantly mediate contraction caused by KCl, and NK2 receptors predominantly mediate contraction elicited by capsaicin in guinea pig airway smooth muscle.

Role of phospholipase A2 (group I secreted) in the genesis of basal tone in the internal anal sphincter smooth muscle

2007 ◽  
Vol 293 (5) ◽  
pp. G979-G986 ◽  
Author(s):  
Márcio A. F. de Godoy ◽  
Satish Rattan
Keyword(s):  
Smooth Muscle ◽  
Anal Sphincter ◽  
Internal Anal Sphincter ◽  
Critical Role ◽  
Smooth Muscles ◽  
Electrical Field Stimulation ◽  
Group I ◽  
Basal Tone ◽  
Bromoenol Lactone

The role of phospholipase A2 (PLA2) in the genesis of basal tone in the internal anal sphincter (IAS) is not known. We determined the effects of PLA2 and inhibitors on the basal tone and intraluminal pressures (IASP) in the rat IAS vs. rectal smooth muscles (RSM). In addition, we determined the correlations between the IAS tone, PLA2 levels, and the actual enzymatic activity. Inhibition of PLA2 by 4-bromophenacyl bromide (universal inhibitor of PLA2) and MJ33 [selective inhibitor of secreted isoform of PLA2 (sPLA2)] caused concentration-dependent decrease in the IAS tone and in the IASP. Maximal decreases in the IAS tone and IASP by 4-bromophenacyl bromide and MJ33 were 58.8 ± 6.9 and 51.5 ± 6.3%, and 66.7 ± 5.1 and 79.8 ± 8.2%, respectively. The sPLA2 inhibitors were ∼100 times more potent in decreasing the IASP than the mean blood pressure. Conversely, the selective inhibitors of the cytosolic and calcium-independent PLA2 arachidonyl trifluoromethyl ketone and bromoenol lactone, respectively, produced no significant effect. The IAS had characteristically higher levels of sPLA2 activity (26.5 ± 4.9 μmol·min−1·ml−1) vs. the RSM (3.2 ± 0.4 μmol·min−1·ml−1), and higher levels of sPLA2 as shown by Western blot and RT-PCR. Interestingly, administration of sPLA2 transformed RSM into the tonic smooth muscle like that of the IAS: it developed basal tone and relaxed in response to the electrical field stimulation. From the present data, we conclude that sPLA2 plays a critical role in the genesis of tone in the IAS. PLA2 inhibitors may provide potential therapeutic target for treating anorectal motility disorders.

Role of l-Ca2+ channels in intestinal pacing in wild-type and W/WV mice

2005 ◽  
Vol 288 (3) ◽  
pp. G439-G446 ◽  
Author(s):  
Geoffrey Boddy ◽  
E. E. Daniel
Keyword(s):  
Smooth Muscle ◽  
Bay K 8644 ◽  
Wild Type ◽  
Uniform Contraction ◽  
Mouse Intestine ◽  
Cells Of Cajal ◽  
Channel Currents ◽  
Ca2 Channels ◽  
Frequency Gradient

Rhythmic contractions generating transit in the digestive tract are paced by a network of cells called interstitial cells of Cajal (ICC) found in the myenteric plexus (MP). ICC generate cyclic depolarizations termed “slow waves” that are passively transmitted to the smooth muscle to initiate contractions. The opening of l-Ca2+ channels are believed to be primarily responsible for the influx of calcium generating a contraction in smooth muscle. However, l-Ca2+ channels are not thought to be important in generating the pacing current found in ICC. Using intact segments of circular (CM) and longitudinal (LM) muscle from wild-type mice and mice lacking c-kit kinase (W/WV), we found that l-Ca2+ channel currents are required for pacing at normal frequencies to occur. Application of 1 μM nicardipine caused a significant decrease in contraction amplitude and frequency in LM and CM that was successfully blocked with BAY K 8644. Nicardipine also abolished the pacing gradient found throughout the intestines, resulting in a uniform contraction frequency of 30–40/minute. Stimulating l-Ca2+ channels with BAY K 8644 neither removed nor recovered the pacing gradient. W/WV mice, which lack ICC-MP, also exhibited a pacing gradient in LM. Application of nicardipine to LM segments of W/WV mouse intestine did not reduce pacing frequency, and in jejunum, resulted in a slight increase. BAY K 8644 did not affect pacing frequency in W/WV tissue. In conclusion, we found that l-Ca2+ channel activity was required for normal pacing frequencies and to maintain the pacing frequency gradient found throughout the intestines in wild-type but not in W/WV mouse intestine.

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