The vaso-contractile action of zooxanthellatoxin-B from a marine dinoflagellate is mediated via Ca2+ influx in the rabbit aorta

2001 ◽  
Vol 79 (12) ◽  
pp. 1030-1035 ◽  
Author(s):  
Takahiro Moriya ◽  
Ken-Ichi Furukawa ◽  
Hideshi Nakamura ◽  
Akio Murai ◽  
Yasushi Ohizumi
Keyword(s):  
Channel Blocker ◽  
Rabbit Aorta ◽  
Simultaneous Recording ◽  
Channel Blockers ◽  
Dependent Manner ◽  
Free Solution ◽  
Half Maximum ◽  
Concentration Dependent Manner ◽  
Time Required

We previously showed that zooxanthellatoxin-B, isolated from dinoflagellate, caused a sustained contraction of the aorta in an external Ca2+-dependent manner. To clarify the role of Ca2+ in this action, we examined the effects of zooxanthellatoxin-B as well as a depolarizing stimulus (60 mM KCl), using the simultaneous recording for cytosolic Ca2+ level (fura-2) and developed tension in the rabbit aorta. KCl (60 mM) elicited a rapid cytosolic Ca2+ elevation followed by a pronounced contraction, and time required for half-maximum contraction was 2 min. Zooxanthellatoxin-B caused an increase in cytosolic Ca2+ followed by a gradual contraction, with a time for half-maximum contraction of 5–10 min in a concentration-dependent manner. We found a strong correlation between Ca2+ elevation and the contraction in zooxanthellatoxin-B action. In a Ca2+-free solution, zooxanthellatoxin-B caused neither the contraction nor the increase in cytosolic Ca2+. Furthermore, both pre- and post-treatment with verapamil, a voltage-operated Ca2+-channel blocker, partially suppressed both an increase in cytosolic Ca2+ and the contraction by zooxanthellatoxin-B. Zooxanthellatoxin-B-induced contraction was also inhibited by other voltage-operated Ca2+-channel blockers: nifedipine or diltiazem. These results suggest that zooxanthellatoxin-B-elicited contraction is caused by a Ca2+ influx into the smooth muscle cells, partially via voltage-operated Ca2+ channels.Key words: zooxanthellatoxin, Ca2+ imaging, rabbit aorta, contraction, voltage-operated Ca2+-channels.

Ca dependence of Na influx during treatment of rabbit aorta with NE and high K solutions

1988 ◽  
Vol 254 (1) ◽  
pp. C75-C83 ◽  
Author(s):  
P. I. Aaronson ◽  
A. W. Jones
Keyword(s):  
Rabbit Aorta ◽  
Dependent Manner ◽  
Free Solution ◽  
Concentration Dependent Manner ◽  
High K ◽  
Ca Antagonist ◽  
Intracellular Ca ◽  
Isolated Rabbit Aorta ◽  
Ca Agonist

Cellular influx of 24Na was measured in isolated rabbit aorta during stimulation with 10 microM norepinephrine (NE) or depolarization with 80 mM K solution, using a pulse-labeling, cold-wash technique. NE caused a two- to threefold increase in Na influx; a smaller but significant increase was also observed in depolarized tissues. Basal and NE-induced fluxes at 1 min were significantly increased by a 20-min preincubation in a Ca-free solution containing 2 mM EGTA; elevation of [Mg] in this solution reduced these effects. The high K-induced influx was prevented by a combination of low Ca (30 microns) and elevated Mg (10 mM). The Ca agonist, BAY-K 8644, increased 24Na influx. The Ca antagonist, diltiazem, inhibited the depolarization-stimulated 24Na influx in a concentration-dependent manner, but was less effective in blocking the response to NE. Extension of the preincubation in NE plus Ca-free medium from 30 s to 15 min decreased the influx response and contraction. After exposure to NE in Ca-free solution, 24Na influx remained elevated 10 min after washing out NE in the continued absence of Ca. A second exposure to NE at that time did not increase influx. We propose that a component of 24Na influx during excitation depends directly on a rise in intracellular [Ca]. The role of an indirect effect of [Ca] on metabolic H+ production with subsequent stimulation of the Na+-H+ exchange may also be a factor.

Effect of disulfonic stilbene anion-channel blockers on the guinea-pig myocardium

1985 ◽  
Vol 63 (8) ◽  
pp. 912-917 ◽  
Author(s):  
Arda-E-Viraf M. Minocherhomjee ◽  
Basil D. Roufogalis ◽  
John H. McNeill
Keyword(s):  
Guinea Pig ◽  
Anion Channel ◽  
Channel Blockers ◽  
Dependent Manner ◽  
Maximal Inhibition ◽  
Concentration Dependent Manner ◽  
Covalent Interaction ◽  
Disulfonic Stilbene ◽  
Frequency Of Stimulation

The role of anions in the maintenance of tension in electrically driven left atria isolated from guinea pigs has been examined. The disulfonic stilbene anion-channel blockers SITS (4-acetamido-4′-isothiocyanostilbene 2′-disulfonate) and DIDS (4,4′-diisothiocyano-2,2′-stilbene disulfonate) decreased the contractile force developed in a time- and concentration-dependent manner. As in the red cell anion channel, DIDS was more potent than SITS, but the maximal inhibition of tension produced by N-(4-azido-2-nitrophenyl)-2-aminoethyl sulfonate (NAP-taurine) was considerably lower than the near maximal inhibition produced by SITS and DIDS. The inhibition by SITS and DIDS was irreversible, suggesting a covalent interaction, and could not be overcome by increasing the calcium concentration or the frequency of stimulation. Consistent with a requirement for chloride anion, substitution of chloride and bicarbonate by the impermeant anion gluconate did not support contraction, while only partial tension was maintained with the lipophilic anions acetate and thiocyanate. Incubation of atria with 400 μM SITS blocked both 36Cl and 45Ca uptake to a similar extent, whereas the efflux of both these ions was not affected by incubation of the atria with SITS. The blockade by disulfonic stilbene anion-channel blockers of the contraction of the guinea pig myocardium may result from impairment of excitation–contraction coupling.

scholarly journals The Role of K+, Ca2+ channels and Endothelial Hyperpolarizing Factors in Vasorelaxation Induced by Tribulus terrestris

2021 ◽  
Vol 2 (1) ◽  
pp. 94-100
Author(s):  
Thamer M. Bashir ◽  
Omar A.M. Al-Habib
Keyword(s):  
Methanolic Extract ◽  
K Channel ◽  
Tribulus Terrestris ◽  
Channel Blockers ◽  
Dependent Manner ◽  
The Novel ◽  
Concentration Dependent Manner ◽  
Relaxant Effect ◽  
Calcium Ion Channels

The present study focused on the relaxant effect of themethanolic extract (ME) of Tribulus terristris on rats’ thoracic aortae and included the study of underlying vasorelaxation mechanisms. The methanolic extract produced concentration-dependent relaxation in rats’ aorta. The methanolic extract produced concentration-dependent relaxation in the aortic rings. The use of different K+ channel blockers (BaCl2, 4-AP, GLIB, and TEA) indicated that Kv, KATP, KIR, and KCa and L-type Ca channels played no role in the methanolic extractinduced relaxation. However, with respect to endothelium-derived hyperpolarizing factors, PGI2 and sGC produced a mild inhibition in the relaxation response to ME while NO produced no effect at all. Based on the novel results of the current study, it can be concluded that T. terrestris methanolic extract (ME) mediated relaxation in isolated rat aortic tissues in a concentration-dependent manner. Moreover, we discovered that ME-mediated relaxation is endothelium-dependent and that potassium and calcium ion channels play no role in this relaxation with a limited role of PGI2 and sGC.

TEA inhibits ACh-induced EDRF release: endothelial Ca(2+)-dependent K+ channels contribute to vascular tone

1994 ◽  
Vol 267 (3) ◽  
pp. H1135-H1141 ◽  
Author(s):  
E. Demirel ◽  
J. Rusko ◽  
R. E. Laskey ◽  
D. J. Adams ◽  
C. van Breemen
Keyword(s):  
Endothelial Cells ◽  
Patch Clamp ◽  
Outward Current ◽  
Rabbit Aorta ◽  
K Channel ◽  
Channel Blockers ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
K Channels ◽  
Donor Segment

The effects of K(+)-channel blockers on the acetylcholine (ACh)-induced relaxation of vascular smooth muscle, intracellular free Ca2+ concentration ([Ca2+]i) elevation, and ACh-evoked outward K+ current of endothelial cells of rabbit aorta were studied using bioassay, spectrofluorimetry, and patch-clamp techniques, respectively. In bioassay experiments, ACh caused relaxation of endothelium-denuded aortic rings in a concentration-dependent manner when perfused through an endothelium-intact donor segment of aorta but not when perfused directly onto the recipient aortic ring. ACh-induced relaxation was inhibited by perfusion of tetraethylammonium ions (TEA; 5 mM) through the donor but not by perfusion directly onto the recipient segment. Glibenclamide had no effect on ACh-induced relaxation of the bioassay ring in either situation. ACh increased [Ca2+]i at the endothelial surface of aortic strips but not at the adventitial surface. TEA inhibited ACh-induced [Ca2+]i elevation, whereas glibenclamide had no effect. In patch-clamp experiments with freshly isolated endothelial cells, ACh evoked a biphasic outward current which was completely abolished by TEA (3 mM). It is concluded that Ca(2+)-dependent K+ channels are important for increasing [Ca2+]i during agonist stimulation and consequently for the synthesis/release of endothelium-derived relaxing factors (EDRFs). Furthermore, endothelial ATP-sensitive K+ channels do not contribute to ACh-induced relaxation or evoke an increase in endothelial [Ca2+]i of rabbit thoracic aorta.

Vasorelaxing Activity of Stilbenoid and Phenanthrene Derivatives from Brasiliorchis porphyrostele: Involvement of Smooth Muscle CaV1.2 Channels

Planta Medica ◽  
2020 ◽  
Vol 86 (09) ◽  
pp. 631-642
Author(s):  
Watcharee Waratchareeyakul ◽  
Fabio Fusi ◽  
Miriam Durante ◽  
Amer Ahmed ◽  
Walter Knirsch ◽  
...  
Keyword(s):  
Channel Blocker ◽  
Antihypertensive Agents ◽  
Dependent Manner ◽  
Vascular Effects ◽  
Concentration Dependent Manner ◽  
Spasmolytic Activity ◽  
Depth Analysis ◽  
Cav1.2 Channels ◽  
Vasorelaxant Activity

AbstractFive compounds, 3,4′-dihydroxy-3′,5,5′-trimethoxydihydrostilbene, 1; 3,4′-ihydroxy-3′,5′-dimethoxydihydrostilbene, 2; 3,4′-dihydroxy-5,5′-dimethoxydihydrostilbene, 3; 9,10-dihydro-2,7-dihydroxy-4,6-dimethoxyphenanthrene, 4; and the previously unreported 1,2,6,7-tetrahydroxy-4-methoxyphenanthrene, 5 were isolated from the South American orchid, Brasiliorchis porphyrostele. An in-depth analysis of their vascular effects was performed on in vitro rat aorta rings and tail main artery myocytes. Compounds 1 – 4 were shown to possess vasorelaxant activity on rings pre-contracted by the α 1 receptor agonist phenylephrine, the CaV1.2 stimulator (S)-(−)-Bay K 8644, or depolarized with high K+ concentrations. However, compound 5 was active solely on rings stimulated by 25 mM but not 60 mM K+. The spasmolytic activity of compounds 1 and 4 was significantly affected by the presence of an intact endothelium. The KATP channel blocker glibenclamide and the KV channel blocker 4-aminopyridine significantly antagonized the vasorelaxant activity of compounds 4 and 1, respectively. In patch-clamp experiments, compounds 1 – 4 inhibited Ba2+ current through CaV1.2 channels in a concentration-dependent manner, whereas neither compound 4 nor compound 1 affected K+ currents through KATP and KV channels, respectively. The present in vitro, comprehensive study demonstrates that Brasiliorchis porphyrostele may represent a source of vasoactive agents potentially useful for the development of novel antihypertensive agents that has now to be validated in vivo in animal models of hypertension.

The P-element-induced silencing effect of KP transposons is dose dependent in Drosophila melanogaster

Genome ◽  
2011 ◽  
Vol 54 (9) ◽  
pp. 752-762 ◽  
Author(s):  
Alireza Sameny ◽  
John Locke
Keyword(s):  
Drosophila Melanogaster ◽  
Critical Role ◽  
Mutagenic Effect ◽  
P Element ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
P Elements ◽  
Single Well ◽  
Dose Dependent

Transposable elements are found in the genomes of all eukaryotes and play a critical role in altering gene expression and genome organization. In Drosophila melanogaster, transposable P elements are responsible for the phenomenon of hybrid dysgenesis. KP elements, a deletion-derivative of the complete P element, can suppress this mutagenic effect. KP elements can also silence the expression of certain other P-element-mediated transgenes in a process called P-element-dependent silencing (PDS), which is thought to involve the recruitment of heterochromatin proteins. To explore the mechanism of this silencing, we have mobilized KP elements to create a series of strains that contain single, well-defined KP insertions that show PDS. To understand the quantitative role of KP elements in PDS, these single inserts were combined in a series of crosses to obtain genotypes with zero, one, or two KP elements, from which we could examine the effect of KP gene dose. The extent of PDS in these genotypes was shown to be dose dependent in a logarithmic rather than linear fashion. A logarithmic dose dependency is consistent with the KP products interacting with heterochromatic proteins in a concentration-dependent manner such that two molecules are needed to induce gene silencing.

Protein kinase C potentiates cAMP-stimulated mouse duodenal mucosal bicarbonate secretion in vitro

2004 ◽  
Vol 286 (5) ◽  
pp. G814-G821 ◽  
Author(s):  
Bi-Guang Tuo ◽  
Jimmy Y. C. Chow ◽  
Kim E. Barrett ◽  
Jon I. Isenberg
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Duodenal Mucosa ◽  
Bicarbonate Secretion ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Ussing Chambers ◽  
Duodenal Bicarbonate Secretion

PKC has been shown to regulate epithelial Cl- secretion in a variety of models. However, the role of PKC in duodenal mucosal bicarbonate secretion is less clear. We aimed to investigate the role of PKC in regulation of duodenal mucosal bicarbonate secretion. Bicarbonate secretion by murine duodenal mucosa was examined in vitro in Ussing chambers using a pH-stat technique. PKC isoform expression and activity were assessed by Western blotting and in vitro kinase assays, respectively. PMA (an activator of PKC) alone had no effect on duodenal bicarbonate secretion or short-circuit current ( Isc). When PMA and dibutyryl-cAMP (db-cAMP) were added simultaneously, PMA failed to alter db-cAMP-stimulated duodenal bicarbonate secretion or Isc ( P > 0.05). However, a 1-h preincubation with PMA potentiated db-cAMP-stimulated duodenal bicarbonate secretion and Isc in a concentration-dependent manner (from 10-8 to 10-5M) ( P < 0.05). PMA preincubation had no effects on carbachol- or heat-stable toxin-stimulated bicarbonate secretion. Western blot analysis revealed that PKCα, -γ, -ϵ, -θ, -μ, and -ι/λ were expressed in murine duodenal mucosa. Ro 31–8220 (an inhibitor active against PKCϵ, -α, -β, and -γ), but not Gö 6983 (an inhibitor active against PKCα, -γ, -β, and -δ), reversed the potentiating effect of PMA on db-cAMP-stimulated bicarbonate secretion. PMA also time- and concentration-dependently increased the activity of PKCϵ, an effect that was prevented by Ro 31–8220 but not Gö 6983. These results demonstrate that activation of PKC potentiates cAMP-stimulated duodenal bicarbonate secretion, whereas it does not modify basal secretion. The effect of PKC on cAMP-stimulated bicarbonate secretion is mediated by the PKCϵ isoform.

scholarly journals Sec1p directly stimulates SNARE-mediated membrane fusion in vitro

2004 ◽  
Vol 167 (1) ◽  
pp. 75-85 ◽  
Author(s):  
Brenton L. Scott ◽  
Jeffrey S. Van Komen ◽  
Hassan Irshad ◽  
Song Liu ◽  
Kirilee A. Wilson ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Fusion ◽  
Membrane Trafficking ◽  
Snare Complex ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Bud Neck ◽  
Precise Role

Sec1 proteins are critical players in membrane trafficking, yet their precise role remains unknown. We have examined the role of Sec1p in the regulation of post-Golgi secretion in Saccharomyces cerevisiae. Indirect immunofluorescence shows that endogenous Sec1p is found primarily at the bud neck in newly budded cells and in patches broadly distributed within the plasma membrane in unbudded cells. Recombinant Sec1p binds strongly to the t-SNARE complex (Sso1p/Sec9c) as well as to the fully assembled ternary SNARE complex (Sso1p/Sec9c;Snc2p), but also binds weakly to free Sso1p. We used recombinant Sec1p to test Sec1p function using a well-characterized SNARE-mediated membrane fusion assay. The addition of Sec1p to a traditional in vitro fusion assay moderately stimulates fusion; however, when Sec1p is allowed to bind to SNAREs before reconstitution, significantly more Sec1p binding is detected and fusion is stimulated in a concentration-dependent manner. These data strongly argue that Sec1p directly stimulates SNARE-mediated membrane fusion.

scholarly journals Citrus bergamiaRisso Elevates Intracellular Ca2+in Human Vascular Endothelial Cells due to Release of Ca2+from Primary Intracellular Stores

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Purum Kang ◽  
Seung Ho Han ◽  
Hea Kyung Moon ◽  
Jeong-Min Lee ◽  
Hyo-Keun Kim ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Channel Blocker ◽  
Vascular Endothelial Cells ◽  
Umbilical Vein ◽  
Dependent Manner ◽  
Vascular Endothelial ◽  
Concentration Dependent Manner ◽  
Carbonyl Cyanide ◽  
Intracellular Ca ◽  
Umbilical Vein Endothelial Cells

The purpose of the present study is to examine the effects of essential oil ofCitrus bergamiaRisso (bergamot, BEO) on intracellular Ca2+in human umbilical vein endothelial cells. Fura-2 fluorescence was used to examine changes in intracellular Ca2+concentration[Ca2+]i. In the presence of extracellular Ca2+, BEO increased[Ca2+]i, which was partially inhibited by a nonselective Ca2+channel blocker La3+. In Ca2+-free extracellular solutions, BEO increased[Ca2+]iin a concentration-dependent manner, suggesting that BEO mobilizes intracellular Ca2+. BEO-induced[Ca2+]iincrease was partially inhibited by a Ca2+-induced Ca2+release inhibitor dantrolene, a phospholipase C inhibitor U73122, and an inositol 1,4,5-triphosphate (IP3)-gated Ca2+channel blocker, 2-aminoethoxydiphenyl borane (2-APB). BEO also increased[Ca2+]iin the presence of carbonyl cyanide m-chlorophenylhydrazone, an inhibitor of mitochondrial Ca2+uptake. In addition, store-operated Ca2+entry (SOC) was potentiated by BEO. These results suggest that BEO mobilizes Ca2+from primary intracellular stores via Ca2+-induced and IP3-mediated Ca2+release and affect promotion of Ca2+influx, likely via an SOC mechanism.

Metabotropic glutamate receptor agonist-induced hyperpolarizations in rat basolateral amygdala neurons: receptor characterization and ion channels

1996 ◽  
Vol 76 (5) ◽  
pp. 3059-3069 ◽  
Author(s):  
K. H. Holmes ◽  
N. B. Keele ◽  
V. L. Arvanov ◽  
P. Shinnick-Gallagher
Keyword(s):  
Dicarboxylic Acid ◽  
Glutamate Receptor ◽  
Basolateral Amygdala ◽  
Metabotropic Glutamate Receptor ◽  
Outward Current ◽  
Channel Blockers ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Metabotropic Glutamate ◽  
Outward Currents

1. Metabotropic glutamate receptor (mGluR)-agonist-induced hyperpolarizations and corresponding outward currents were analyzed in basolateral amygdala (BLA) neurons in rat brain slice preparations with current-clamp and single-electrode voltage-clamp recording to characterize the mGluR subtype(s) and the ion channel(s) mediating this response. 2. The mGluR agonist (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) induced a membrane hyperpolarization or outward current in BLA neurons in a concentration-dependent manner (median effective concentration = 34 microM; range = 10-200 microM); the 1S,3R-ACPD hyperpolarizations are recorded in 89% of neurons that accommodate or cease firing in response to a 400-ms depolarizing current injection (0.5 nA). 3. mGluR agonists elicited hyperpolarizations or outward currents in a concentration-dependent manner in the following rank order of potency: (2S,3S,4S)-alpha-(carboxycyclopropyl)glycine (L-CCG-I) > 1S,3R-ACPD > (s)-4-carboxyphenylglycine = (RS)-4-carboxy-3-hydroxyphenylglycine (4C3HPG) > L-aminophosphonobutyric acid > (1S,3S)-1-amino-cyclopentane-1,3-dicarboxylic acid. In contrast, the mGluR agonists quisqualate and ibotenate induced only depolarizations in the presence of D-2-amino-5-phosphonovalerate and 6-cyano-7-nitroquinoxaline-2,3-dione in BLA neurons. 4. The 1S,3R-ACPD-induced outward current is mediated through a large-conductance calcium-dependent potassium (BK) conductance. The BK channel blockers iberiotoxin and charybdotoxin blocked the response, as did the potassium channel blockers tetraethylammonium and 4-aminopyridine; the small-conductance calcium-activated potassium channel blocker apamin did not affect the response. 5. The mGluR-agonist-induced hyperpolarization is blocked in amygdala slices from animals pretreated with pertussis toxin (PTX). 1S,3R-ACPD hyperpolarizations were recorded in neurons contralateral but not ipsilateral to the site of PTX injection. 6. The antagonist (+/-)-alpha-methyl-4-carboxyphenylglycine (MCPG, 500 microM) reduced significantly the 1S,3R-ACPD-induced hyperpolarization. 7. In conclusion, the relative potency of L-CCG-I and 4C3HPG in evoking only hyperpolarizations (outward currents) in accommodating neurons, and the observation that MCPG (500 microM) reduces the hyperpolarization, suggest that a group-II-like mGluR underlies the hyperpolarizing response. The mGluR-induced response is sensitive to iberiotoxin and to pretreatment with PTX, suggesting activation of BK channels through a group II mGluR linked to a PTX-sensitive G protein in BLA neurons.

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