scholarly journals Effect of sphingosine derivatives on calcium fluxes in thyroid FRTL-5 cells

1994 ◽  
Vol 299 (1) ◽  
pp. 213-218 ◽  
Author(s):  
K Törnquist ◽  
E Ekokoski
Keyword(s):  
Elevated Level ◽  
Channel Blocker ◽  
Thyroid Stimulating Hormone ◽  
Thyroid Cell ◽  
Dependent Manner ◽  
Myristate Acetate ◽  
Permeabilized Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Dose Dependent ◽  
In Cells

The effects of sphingosine derivatives on Ca2+ fluxes were investigated in thyroid FRTL-5 cells labelled with Fura 2. Addition of sphingosylphosphocholine (SPC) or sphingosine (SP) increased intracellular free Ca2+ ([Ca2+]i) in a dose-dependent manner. At the highest dose tested (30 microM), the response was biphasic: a rapid transient increase in [Ca2+]i, followed by a new, elevated, level of [Ca2+]i. Both phases of the SPC-evoked increase in [Ca2+]i were dependent on extracellular Ca2+, whereas only the SP-evoked elevated level of [Ca2+]i was dependent on the influx of Ca2+. Both compounds released sequestered Ca2+ from thapsigargin- and inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ pools. In addition, the increase in [Ca2+]i in response to SPC, but not to SP, was attenuated in cells treated with phorbol myristate acetate or with the putative Ca(2+)-channel blocker SKF 96365, and in cells pretreated with pertussis toxin for 24 h. SPC did not activate the production of IP3. Furthermore, both SPC and SP released sequestered Ca2+ from permeabilized cells. We observed that SPC, but not SP, stimulated release of [3H]arachidonate from cells prelabelled with [3H]arachidonate for 24 h. Both SPC and SP stimulated the incorporation of [3H]thymidine into DNA in cells grown in the absence of thyroid-stimulating hormone (TSH). The results suggest that sphingosine derivatives are putative regulators of Ca2+ fluxes in FRTL-5 cells, and that SP and SPC may act on [Ca2+]i via different mechanisms. Furthermore, both SP and SPC may be of importance in modulating thyroid-cell proliferation.

scholarly journals Role of leukemia inhibitor factor (LIF) in decidualisation of murine uterine stromal cells in vitro

2004 ◽  
Vol 181 (3) ◽  
pp. 477-492 ◽  
Author(s):  
AA Fouladi Nashta ◽  
CV Andreu ◽  
N Nijjar ◽  
JK Heath ◽  
SJ Kimber
Keyword(s):  
In Vitro Culture ◽  
Stromal Cells ◽  
Control Level ◽  
Calf Serum ◽  
Prostaglandin E ◽  
Dependent Manner ◽  
Alp Activity ◽  
Dose Dependent ◽  
In Cells

Decidualisation of uterine stromal cells is a prerequisite for implantation of the embryo in mice. Here we have used an in vitro culture system in which stromal cells decidualise as indicated by a number of markers, including an increase in alkaline phosphatase (ALP) activity. The latter was used as a quantitative marker of decidualisation in the presence of low (2%) fetal calf serum. Prostaglandin E(2) (PGE(2)), which is known to induce decidualisation, increased ALP activity, and this effect was blocked in a dose-dependent manner by indomethacin. Leukemia inhibitory factor (LIF) was then examined, but it had no effect on PGE(2) secretion. However, LIF suppressed ALP activity in a dose-dependent manner in the presence of 2% serum, while an inhibitor of LIF that competes for binding to its receptor reversed the effect of LIF and increased ALP activity above the control level. In serum-free cultures, stromal cells differentiated rapidly, and no differences were observed between LIF-treated and untreated cultures. Stromal cells produce LIF during in vitro culture, and this peaked at 48 h. Freshly collected stromal cells from both day-2 and -4 pregnant mice expressed mRNA for the LIF receptor, and the transcript level was higher in cells isolated on day 4. However, no differences were observed in the relative levels of transcripts in cells from day 2 and day 4 after culture, nor were there differences between the LIF-treated cultures and controls. Therefore, in this study, we have shown that LIF suppresses decidualisation of murine uterine stromal cells in the presence of serum, this is not due to the regulation of PGE(2) secretion by stromal cells.

scholarly journals Endogenous H2S is required for hypoxic sensing by carotid body glomus cells

2012 ◽  
Vol 303 (9) ◽  
pp. C916-C923 ◽  
Author(s):  
Vladislav V. Makarenko ◽  
Jayasri Nanduri ◽  
Gayatri Raghuraman ◽  
Aaron P. Fox ◽  
Moataz M. Gadalla ◽  
...  
Keyword(s):  
Carotid Body ◽  
Time Course ◽  
Channel Blocker ◽  
Primary Site ◽  
Dependent Manner ◽  
Free Medium ◽  
Adult Rats ◽  
Glomus Cells ◽  
Dose Dependent ◽  
Carotid Body Glomus Cells

H2S generated by the enzyme cystathionine-γ-lyase (CSE) has been implicated in O2 sensing by the carotid body. The objectives of the present study were to determine whether glomus cells, the primary site of hypoxic sensing in the carotid body, generate H2S in an O2-sensitive manner and whether endogenous H2S is required for O2 sensing by glomus cells. Experiments were performed on glomus cells harvested from anesthetized adult rats as well as age and sex-matched CSE+/+ and CSE−/− mice. Physiological levels of hypoxia (Po2 ∼30 mmHg) increased H2S levels in glomus cells, and dl-propargylglycine (PAG), a CSE inhibitor, prevented this response in a dose-dependent manner. Catecholamine (CA) secretion from glomus cells was monitored by carbon-fiber amperometry. Hypoxia increased CA secretion from rat and mouse glomus cells, and this response was markedly attenuated by PAG and in cells from CSE−/− mice. CA secretion evoked by 40 mM KCl, however, was unaffected by PAG or CSE deletion. Exogenous application of a H2S donor (50 μM NaHS) increased cytosolic Ca2+ concentration ([Ca2+]i) in glomus cells, with a time course and magnitude that are similar to that produced by hypoxia. [Ca2+]i responses to NaHS and hypoxia were markedly attenuated in the presence of Ca2+-free medium or cadmium chloride, a pan voltage-gated Ca2+ channel blocker, or nifedipine, an L-type Ca2+ channel inhibitor, suggesting that both hypoxia and H2S share common Ca2+-activating mechanisms. These results demonstrate that H2S generated by CSE is a physiologic mediator of the glomus cell's response to hypoxia.

Altering the cellular mechanical force balance results in integrated changes in cell, cytoskeletal and nuclear shape

1992 ◽  
Vol 103 (4) ◽  
pp. 1215-1222 ◽  
Author(s):  
J.R. Sims ◽  
S. Karp ◽  
D.E. Ingber
Keyword(s):  
Shape Control ◽  
Nuclear Shape ◽  
Force Balance ◽  
Dependent Manner ◽  
Integrin Receptors ◽  
Permeabilized Cells ◽  
Capillary Endothelial Cells ◽  
Shape Determination ◽  
Dose Dependent

Studies were carried out with capillary endothelial cells cultured on fibronectin (FN)-coated dishes in order to analyze the mechanism of cell and nuclear shape control by extracellular matrix (ECM). To examine the role of the cytoskeleton in shape determination independent of changes in transmembrane osmotic pressure, membranes of adherent cells were permeabilized with saponin (25 micrograms/ml) using a buffer that maintains the functional integrity of contractile microfilaments. Real-time videomicroscopic studies revealed that addition of 250 microM ATP resulted in time-dependent retraction and rounding of permeabilized cells and nuclei in a manner similar to that observed in intact living cells following detachment using trypsin-EDTA. Computerized image analysis confirmed that permeabilized cells remained essentially rigid in the absence of ATP and that retraction was stimulated in a dose-dependent manner as the concentration of ATP was raised from 10 to 250 microM. Maximal rounding occurred by 30 min with projected cell and nuclear areas being reduced by 69 and 41%, respectively. ATP-induced rounding was also accompanied by a redistribution of microfilaments resulting in formation of a dense net of F-actin surrounding retracted nuclei. Importantly, ATP-stimulated changes in cell, cytoskeletal, and nuclear form were prevented in permeabilized cells using a synthetic myosin peptide (IRICRKG) that has been previously shown to inhibit actomyosin filament sliding in muscle. In contrast, both the rate and extent of cell and nuclear rounding were increased in permeabilized cells exposed to ATP when the soluble FN peptide, GRGDSP, was used to dislodge immobilized FN from cell surface integrin receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Rat Prl and TSH secretion are regulated differently by K(+)-channel blockers

1994 ◽  
Vol 266 (1) ◽  
pp. E39-E43 ◽  
Author(s):  
X. Wang ◽  
T. Inukai ◽  
M. A. Greer ◽  
S. E. Greer
Keyword(s):  
Channel Blocker ◽  
Cell Types ◽  
Inhibitory Effect ◽  
Thyroid Stimulating Hormone ◽  
K Channel ◽  
Channel Blockers ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
K Channels ◽  
Tsh Secretion

All four different K(+)-channel blockers [tetraethylammonium (TEA), a nonselective K(+)-channel blocker; tolbutamide, an ATP-sensitive K(+)-channel blocker; quinine and 4-aminopyridine, both primarily voltage-dependent K(+)-channel blockers] stimulated prolactin (Prl) secretion by acutely dispersed anterior pituitary cells but had no effect on thyroid-stimulating hormone (TSH) secretion. TEA stimulated Prl secretion in a dose-dependent manner between 1 microM and 20 mM, but even as high as 20 mM, TEA did not induce TSH secretion. Valinomycin (2 microM), a K+ ionophore, inhibited both basal and TEA-induced Prl secretion. TEA-stimulated Prl secretion was abolished by using a Ca(2+)-depleted medium or adding 10 microM dopamine. TEA did not reverse the inhibitory effect of dopamine on thyrotropin-releasing hormone-induced Prl secretion. Our data indicate that K+ channels may play a role in the secretion of adenohypophysial hormones that is idiosyncratic for each hormone. Differences in the role of K+ channels may reflect differences between the various pituitary cell types in plasma membrane ion channel composition, membrane potential, or the mechanism of exocytosis.

Oxytocin-induced changes in single cell K+ currents and smooth muscle contraction of guinea-pig gastric antrum

1997 ◽  
Vol 136 (5) ◽  
pp. 531-538 ◽  
Author(s):  
Dessislava B Duridanova ◽  
Milena D Nedelcheva ◽  
Hristo S Gagov
Keyword(s):  
Smooth Muscle ◽  
Cell Membrane ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Gastric Antrum ◽  
Dependent Manner ◽  
Response Curves ◽  
Dose Dependent ◽  
In Cells

Abstract To study the effects of oxytocin on both spontaneous phasic contractions and K+ outward currents (IK) of the so-called 'non-target' smooth muscle cells, physiological concentrations of oxytocin ranging between 10−12 mol/l and 10−8 mol/l were applied to smooth muscle preparations and single voltage-clamped cells isolated from the circular layer of the guinea-pig gastric antrum. Oxytocin (10−12mol/l to 10−8 mol/l) suppressed, in a dose-dependent manner, the tetrodotoxin- and atropine-resistant spontaneous phasic contractions and shifted rightward the dose–response curves of 10−7 mol/l charybdotoxin and 10−3mol/l BaCl2. In cells with preloaded intracellular Ca2+ stores, oxytocin (10−12 mol/l to 10−9 mol/l) caused a dose-dependent activation of the charybdotoxin-blockable non-inactivating component of IK (IK(s1)) of single voltage-clamped cells, which was accompanied by hyperpolarization of the cell membranes. 8Lys-vasopressin and 8arg-vasopressin failed to mimic the effects of oxytocin on both contraction and K+ currents. Further, the oxytocin-induced activation of IK(s1) was effectively antagonized by 5× 10−8 mol/l U-73122 or 5× 10−6 mol/l 2-nitro-4-carboxyphenyl N,N-diphenylcarbamate (inhibitors of the cell membrane phospholipase C), as well as by intracellularly applied heparin (selective inhibitor of inositol-1,4,5-trisphosphate (IP3)-induced Ca2+ release channels). In cells incubated in the absence of Ca2+ entry throughout the study, oxytocin (10−9 mol/l) caused a slight and transient increase of IK(s1) amplitudes. Neither ryanodine (10−6 mol/l nor cyclopiazonic acid (10−6 mol/l) were able to restore the IK-activating effect of oxytocin in these cells. The data obtained suggest (i) that selective oxytocin receptors are present on the membranes of guinea-pig antral smooth muscle cells, (ii) that the oxytocin-related relaxation may result from the activation of Ca2+-sensitive K+ conductivity via activation of IP3-induced release of Ca from the submembrane located cisternae of the sarcoplasmic reticulum Ca2+ stores and (iii) in turn, this evokes a non-inactivating component of IK, hyperpolarizing the cell membrane. European Journal of Endocrinology 136 531–538

scholarly journals Thrombin stimulates wortmannin-inhibitable phosphoinositide 3-kinase and membrane blebbing in CHRF-288 cells

1996 ◽  
Vol 314 (3) ◽  
pp. 805-810 ◽  
Author(s):  
Geeta S. VEMURI ◽  
Jin ZHANG ◽  
Rusong HUANG ◽  
James H. KEEN ◽  
Susan E. RITTENHOUSE
Keyword(s):  
G Protein ◽  
Morphological Changes ◽  
Shape Change ◽  
Specific Inhibitor ◽  
Thrombin Receptor ◽  
Dependent Manner ◽  
Permeabilized Cells ◽  
Phosphoinositide 3 Kinase ◽  
Change Response ◽  
Dose Dependent

We have investigated thrombin-stimulated morphological changes and the activation of phosphoinositide 3-kinase (PI 3-K), as manifested by the accumulation of PtdIns(3,4)P2 and PtdIns(3,4,5)P3 (labelled with 32P or myo-[3H]inositol), in CHRF-288 cells, a leukaemic cell line derived from a platelet progenitor cell. We report that these cells, when exposed to thrombin or SFLLRN (the peptide Ser-Phe-Leu-Leu-Arg-Asn, a thrombin-receptor ligand) rapidly change shape, forming membrane ‘blebs’, detectable by differential interference contrast or confocal microscopy, as well as labelled 3-phosphorylated phosphoinositides. The ‘blebs’ are distinguishable from ‘ruffles’ or lamellae, since they do not contain phalloidin-detectable actin. Studies with permeabilized cells indicate that PI 3-K is activated synergistically by thrombin+guanosine 5´-[γ-thio]triphosphate. Two forms of PI 3-K, i.e. PI 3-K(γ) and p85/PI 3-K, regulated by Gβγ subunits of heterotrimeric G-protein and the small G-protein Rho, respectively, are present in these cells, as is true for platelets. Wortmannin, a known potent and specific inhibitor of PI 3-K activities, inhibits thrombin-stimulated accumulation of 3-phosphorylated phosphoinositides in a dose-dependent manner (IC50 ~ 10nM), without affecting phospholipase C activation. Pretreatment of CHRF-288 cells with either wortmannin (100 nM) or an unrelated synthetic PI 3-K inhibitor, LY294002 (50 μM), abolishes thrombin-receptor-stimulated blebbing. These results suggest that thrombin-stimulated accumulation of 3-phosphorylated phosphoinositide(s) is required for the shape-change response in CHRF-288 cells.

scholarly journals Anticonvulsant effect of lercanidipine against pentylenetetrazole induced kindling in mice

2017 ◽  
Vol 6 (9) ◽  
pp. 2134
Author(s):  
Nitya Selvaraj ◽  
Deepa Kameswari ◽  
Ramya Gandhi ◽  
Meher Ali Raja Mohamad
Keyword(s):  
Calcium Channel ◽  
High Voltage ◽  
Scoring System ◽  
Channel Blocker ◽  
Anticonvulsant Effect ◽  
Dependent Manner ◽  
Mice Model ◽  
Dihydropyridine Calcium Channel Blocker ◽  
Dose Dependent

Background: Emerging evidence has demonstrated the role of high-voltage -sensitive activated dihydropyridine (L-type, CaV1.x) channels in the development of epilepsy. Based on that we hypothesized that lercanidipine, a dihydropyridine calcium channel blocker, would protect against Pentylenetetrazole (PTZ) induced kindling in mice model of epilepsy.Methods: Kindling was induced in Swiss albino mice with PTZ in subconvulsive dose (30 mg/kg i.p.) thrice a week for nine weeks and the effect was scored using ‘4 point scoring system’. Rechallenging on the 3rd and 10th day with the same dose of PTZ was carried out after the last chronic dose.Results: The data of the present study demonstrated that pretreatment with lercanidipine (½ h before PTZ, in doses of 1 and 3 mg/kg i.p. daily) alone and in combination with diazepam (2mg/kg i.p.) had decreased the incidence and severity of seizure as well as prolonged the onset of kindling in a dose-dependent manner (p <0.05). On rechallenging, lercanidipine resulted in reduction of seizure score (p <0.05) and increased the seizure latency.Conclusions: The present study suggested that lercanidipine offered neuroprotection against PTZ induced kindling in mice.

scholarly journals Lipoxygenase metabolites of arachidonic acid modulate hematopoiesis

Blood ◽  
1986 ◽  
Vol 67 (6) ◽  
pp. 1675-1679 ◽  
Author(s):  
DS Snyder ◽  
JF Desforges
Keyword(s):  
Arachidonic Acid ◽  
Mononuclear Cells ◽  
Nordihydroguaiaretic Acid ◽  
Cell Types ◽  
Dependent Manner ◽  
Myristate Acetate ◽  
Human Erythropoietin ◽  
Dose Dependent

Abstract Lipoxygenase (LPO) metabolites of arachidonic acid participate in the activation and/or proliferation of a variety of cell types. In this study, we examined the role of LPO metabolites in controlling myelopoiesis and erythropoiesis in vitro. Monocyte depleted cells (MDC) prepared from human whole blood or whole mononuclear cells from human bone marrow were cultured in methylcellulose in the presence of various growth factors. Conditioned media containing human colony stimulating factors (CSF) or the tumor-promoting phorbol ester, phorbol myristate acetate (PMA), were added to induce myelopoiesis. Semipurified human erythropoietin (EPO) was added along with an endogenous source of burst- promoting activity (BPA) to induce erythropoiesis. The LPO inhibitor BW755C blocked all types of colony formation in a dose-dependent manner, with ID50 of 20 and 5 micrograms/mL for myeloid and erythroid colonies, respectively. MDC depleted of T cells were similarly inhibited by BW755C. Similar results were seen with two other LPO inhibitors, 1-phenyl-3-pyrazolidone and butylated hydroxyanisole. A fourth LPO inhibitor, nordihydroguaiaretic acid, inhibited at higher concentrations. Indomethacin, at concentrations that inhibit cyclooxygenase, had no significant effect, either alone or in combination with the LPO inhibitors. These results suggest that certain LPO products may be important mediators of both CSF- and PMA-induced myelopoiesis, and of BPA/EPO-induced erythropoiesis.

Sphingosine 1-phosphate stimulates Na+/H+ exchange in thyroid FRTL-5 cells

1997 ◽  
Vol 272 (3) ◽  
pp. C1052-C1057 ◽  
Author(s):  
K. Tornquist
Keyword(s):  
Phosphatidic Acid ◽  
Phospholipase D ◽  
Mechanism Of Action ◽  
Cell Types ◽  
Dependent Manner ◽  
Tetraacetic Acid ◽  
Sphingosine 1 Phosphate ◽  
Dose Dependent ◽  
Dependent Mechanism ◽  
In Cells

Sphingosine derivatives are potent mitogens in several cell types. Many mitogens activate the Na+/H+ exchange, although the interrelationships between Na+/H+ exchange and mitogenesis are unclear. The present investigation in thyroid FRTL-5 cells shows that sphingosine 1-phosphate (SPP) activates Na+/H+ exchange in a dose-dependent manner in acid-loaded cells. The effect of SPP was abolished in a Na+-free buffer and by pretreatment of the cells with ethylisopropylamiloride. SPP did not affect basal intracellular pH (pHi). SPP stimulated the release of sequestered Ca2+ and a substantial entry of Ca2+. The effect of SPP on pH(i) was abolished in cells incubated in a Ca2+-free buffer, and in cells loaded with the intracellular Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Furthermore, the effect of SPP was abolished in pertussis toxin (PTX)-treated cells. PTX decreased Ca2+ entry only, without affecting the release from intracellular stores. Phosphatidic acid (PA) did not activate Na+/H+ exchange, suggesting that the effect of SPP was not mediated via activation of phospholipase D and the production of PA. Thus one mechanism of action of SPP in FRTL-5 cells appears to be to activate Na+/H+ exchange. This action is mediated via a G protein-dependent mechanism and requires an increase in intracellular free Ca2+.

Isoflurane-induced Dilation of Porcine Coronary Microvessels Is Endothelium Dependent and Inhibited by Glibenclamide

2002 ◽  
Vol 96 (6) ◽  
pp. 1465-1471 ◽  
Author(s):  
A. Kurt Gamperl ◽  
Travis W. Hein ◽  
Lih Kuo ◽  
Brian A. Cason
Keyword(s):  
Potassium Channel ◽  
Sodium Nitroprusside ◽  
Adenosine Triphosphate ◽  
Channel Blocker ◽  
Minimum Alveolar Concentration ◽  
Channel Blockers ◽  
Dependent Manner ◽  
Presence And Absence ◽  
Dose Dependent

Background Isoflurane has been reported to cause dose-dependent constriction in isolated coronary microvessels. However, these results are inconsistent with data from in situ and in vivo heart preparations which show that isoflurane dilates the coronary vasculature. To clarify the direct effects of isoflurane on coronary tone, we measured the response of isolated porcine resistance arterioles (ID, 75 +/- 4.0 microm; range, 41-108 microm) to isoflurane in the presence and absence of adenosine triphosphate-sensitive and Ca2+-activated potassium channel blockers and also after endothelial removal. Methods Subepicardial arterioles were isolated, cannulated, and pressurized to 45 mmHg without flow in a 37 degrees C vessel chamber filled with MOPS buffer (pH = 7.4). After all vessels developed spontaneous (intrinsic) tone, dose-dependent (0.17-0.84 mm; approximately 0.5-2.5 minimum alveolar concentration) isoflurane-mediated effects on vessel ID were studied in the presence and absence of extraluminal glibenclamide (1 microm; an adenosine triphosphate-sensitive channel blocker) or iberiotoxin (100 nm; a Ca2+-activated potassium channel blocker) or before and after endothelial denudation using the nonionic detergent CHAPS (0.4%). Vessel ID was measured using an inverted microscope and videomicrometer, and vasomotor responses were analyzed by normalizing changes in arteriole ID to the dilation observed after exposure to 10-4 m sodium nitroprusside, which causes maximal dilation. Results Isoflurane caused dose-dependent dilation of all coronary arterioles. This vasodilation was 6.0 +/- 0.7 microm at an isoflurane concentration of 0.16 mm (approximately 0.5 minimum alveolar concentration) and 25.3 +/- 2.1 microm at 0.75 mm (approximately 2.5 minimum alveolar concentration). These values represent 18.1 +/- 1.7% and 74.1 +/- 3.3%, respectively, of that observed with 10-4 sodium nitroprusside (34 +/- 3 microm). Glibenclamide, but not iberiotoxin, exposure affected arteriolar dilation in response to isoflurane. Glibenclamide caused a downward displacement of the isoflurane dose-response curve, reducing isoflurane-mediated dilation by an average of 36%. Denuded arterioles showed a marked (approximately 70%) reduction in their ability to dilate in response to isoflurane. Conclusions The authors conclude that isoflurane dilates coronary resistance arterioles in a dose-dependent manner, and that this dilation is partially mediated by adenosine triphosphate-sensitive channels and is highly dependent on the presence of a functioning endothelium.

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