Erg K+ channels modulate contractile activity in the bovine epididymal duct

2008 ◽  
Vol 294 (3) ◽  
pp. R895-R904 ◽  
Author(s):  
Marco Mewe ◽  
Iris Wulfsen ◽  
Anna M. E. Schuster ◽  
Ralf Middendorff ◽  
Günter Glassmeier ◽  
...  
Keyword(s):  
Calcium Release ◽  
Calcium Influx ◽  
Contractile Activity ◽  
Physiological Role ◽  
Inhibitory Effect ◽  
Isometric Tension ◽  
Channel Blockers ◽  
Current Increase ◽  
Epididymal Duct

The expression and functional role of ether-à-go-go-related gene (erg) K+ channels were examined in the bovine epididymal duct. Sperm transit through the epididymal duct relies on spontaneous phasic contractions (SC) of the peritubular smooth muscle wall. Isometric tension studies revealed SC-enhancing effects of the erg channel blockers E-4031, dofetilide, cisapride, and haloperidol and SC-suppressing effects of the activator NS-1643. In the corpus epididymidis, EC50 values of 32 nM and 8.3 μM were determined for E-4031 and NS-1643, respectively. E-4031 was also able to elicit contraction in epithelium-denuded corpus segments, which lacked SC. In the cauda region, E-4031 and NS-1643 exerted effects on agonist-induced contraction similar to those observed in the proximal duct. Experiments with nifedipine and thapsigargin suggested that the excitatory effects of E-4031 depended mainly on external calcium influx and not on intracellular calcium release. Western blot and RT-PCR assays revealed the expression of both, erg1a and erg1b, in all duct regions. Because erg1b appears to predominate in the epididymal duct, patch-clamp experiments were performed on heterologously expressed erg1b channels to investigate the sensitivity of this splice variant to NS-1643. In contrast to its effects on erg1a, NS-1643 induced a concentration-dependent current increase mainly due to a marked leftward shift in erg1b channel activation by ∼30 mV at 10 μM, explaining the inhibitory effect of the drug on epididymal SC. In summary, these data provide strong evidence for a physiological role of erg1 channels in regulating epididymal motility patterns.

scholarly journals Involvement of Alternative Calcium Conductance on Human Myometrial Contractile and Pharmacological Properties

2018 ◽  
Vol 1 (1) ◽  
pp. 100-110
Author(s):  
Éric Rousseau ◽  
Karine Labelle ◽  
Laurence Massenavette
Keyword(s):  
Contractile Activity ◽  
Physiological Role ◽  
Rhythmic Activity ◽  
Isometric Tension ◽  
Human Myometrium ◽  
Trpc Channels ◽  
Tone Frequency ◽  
Experimental Conditions ◽  
Resting Tone

Objective: This study aimed to investigate the physiological role of alternative calcium conduct once contractions triggered by oxytocin and PGF? in human myometrium. This conductance, supported by TRPC and TRPV channels, may provide alternative pathways to control either free intracellular and/or submembrane Ca2+ - concentrations, which in turn will modulate membrane polarization and contractile responses. Study design: Uterine biopsies were obtained from consenting women undergoing elective caesarian delivery at term without labor (N = 29). Isometric tension measurements were performed on uterine strips (n = 174). Amplitudes, frequencies and areas under the curve (AUC) of phasic contractions as well as resting tone were measured under various experimental conditions. Norgestimate, which has been shown to inhibit TRPC isoforms, was added to isolated organ baths to delineate their putative functional involvement. In order to assess the role of TRPV4 channels, rhythmic activity triggered by uterotonic drugs was determined in the absence and presence of either 1 ?M HC-067047 (TRPV4 antagonist) or 100 nM GSK1016790A (TRPV4 agonist). Addition of 50 nM iberiotoxin (IbTX) as well as of 10 ?M NS-1619 was also used to assess the involvement of GKCa channels in controlling uterine reactivity and contractility.Results: Micromolar concentrations of norgestimate consistently decreased the resting tone, frequency and maximal amplitude of oxytocin - and PGF2? - induced contractions. In contrast, the TRPV4 agonist GSK1016790A abolished the rhythmic contractions, resulting in a strong and reversible tocolytic effect. Addition of iberiotoxin (a GKCa blocker) reversed the effects of GSK1016790A, while NS1619 mimicked the rapid tocolytic effects of the TRPV4 agonist. Conclusion: Acute pharmacological inhibition of TRPC channels by norgestimate had minor effects on contractile parameters although resting - tone was lowered. In contrast, selectiveTRPV4 activation led to GKCa activation, which in turn hyperpolarized the myometrial cell membrane, inactivating Ca2+ channels and efficiently abrogated contractile activity. Collectively, these data suggest that alternative calcium conduct ance may play a physiological role in the modulation of myometrial reactivity prior to delivery. A rapid switch from phasic contractions to quiescence by this new class of tocolytics may potentially be of interest in delaying parturition in preterm labor.

scholarly journals New Insights on the Role of TRP Channels in Calcium Signalling and Immunomodulation: Review of Pathways and Implications for Clinical Practice

2021 ◽  
Author(s):  
Saied Froghi ◽  
Charlotte R. Grant ◽  
Radhika Tandon ◽  
Alberto Quaglia ◽  
Brian Davidson ◽  
...  
Keyword(s):  
Immune System ◽  
Calcium Release ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Calcium Influx ◽  
Calcium Signalling ◽  
Chronic Fatigue ◽  
Diverse Range ◽  
Immune System Activation

AbstractCalcium is the most abundant mineral in the human body and is central to many physiological processes, including immune system activation and maintenance. Studies continue to reveal the intricacies of calcium signalling within the immune system. Perhaps the most well-understood mechanism of calcium influx into cells is store-operated calcium entry (SOCE), which occurs via calcium release-activated channels (CRACs). SOCE is central to the activation of immune system cells; however, more recent studies have demonstrated the crucial role of other calcium channels, including transient receptor potential (TRP) channels. In this review, we describe the expression and function of TRP channels within the immune system and outline associations with murine models of disease and human conditions. Therefore, highlighting the importance of TRP channels in disease and reviewing potential. The TRP channel family is significant, and its members have a continually growing number of cellular processes. Within the immune system, TRP channels are involved in a diverse range of functions including T and B cell receptor signalling and activation, antigen presentation by dendritic cells, neutrophil and macrophage bactericidal activity, and mast cell degranulation. Not surprisingly, these channels have been linked to many pathological conditions such as inflammatory bowel disease, chronic fatigue syndrome and myalgic encephalomyelitis, atherosclerosis, hypertension and atopy.

Abstract 579: Increased Role of COX-derived Prostanoids in Regulating Ang II Induced Uterine Artery Contraction at Early Pregnancy in a Transgenic Model of Preeclampsia

Hypertension ◽  
2014 ◽  
Vol 64 (suppl_1) ◽  
Author(s):  
Victor M Pulgar ◽  
Liliya M Yamaleyeva ◽  
Jasmina Varagic ◽  
Carolynne M McGee ◽  
Michael Bader ◽  
...  
Keyword(s):  
Uterine Artery ◽  
Inhibitory Effect ◽  
Isometric Tension ◽  
Late Gestation ◽  
Female Rat ◽  
Ang Ii ◽  
Sprague Dawley ◽  
Vascular Control ◽  
Human Renin

The balance between vasodilatory and vasoconstrictor prostanoids contributes to vascular control during pregnancy. Alterations in this balance are involved in the development of hypertensive pregnancy. The transgenic female rat containing the human angiotensinogen (hAGN) gene mated with the male transgenic containing human renin (hREN) is a model of preeclampsia (TgA), and shows hypertension and proteinuria at late gestation. We investigated the role COX-derived mediators have on contractility of the uterine artery (UA) in TgA rats before the hypertensive phenotype develops. UA were isolated from transgenic TgA (n=9) and Sprague-Dawley (n=7) control rats at 7 days of gestation. UA were mounted in a wire myograph for determinations of isometric tension (DMT USA, 620M). Responses to acetylcholine (ACh), phenylephrine (Phe) and sodium nitroprusside (SNP) were measured in control conditions and after preincubation with indomethacin (Indo, 10-5M). Data were fitted to a dose response curve, vasodilatation was expressed as percent of pre-constriction and sensitivity as pD2 (pD2= -Log [EC50]). Responses to ACh reached similar maximal relaxations (64±8 vs 75±6%, p>0.05), and an increased contraction in TgA UA at ACh >10μM (p<0.05) was eliminated by Indo. Contraction to Phe was similar in both groups with an inhibitory effect of Indo on TgA UA (p<0.05). Relaxation to SNP was lower in TgA vs SD UA (92±2 vs 74±5%, p<0.05), this difference was abolished by Indo. Thus, inhibition of COX enzymes had a greater effect on TgA UA suggesting an imbalance towards an increased prostanoids-derived constrictor tone in TgA UA. This imbalance appears before the hypertensive phenotype is established.

scholarly journals Sodium/Calcium Exchangers Selectively Regulate Calcium Signaling in Mouse Taste Receptor Cells

2010 ◽  
Vol 104 (1) ◽  
pp. 529-538 ◽  
Author(s):  
Steven A. Szebenyi ◽  
Agnieszka I. Laskowski ◽  
Kathryn F. Medler
Keyword(s):  
Calcium Release ◽  
Calcium Influx ◽  
Taste Receptor ◽  
Physiological Role ◽  
Cytosolic Calcium ◽  
Calcium Signals ◽  
Sodium Calcium ◽  
Signaling Mechanisms ◽  
Taste Cells ◽  
Mouse Taste

Taste cells use multiple signaling mechanisms to generate appropriate cellular responses to discrete taste stimuli. Some taste stimuli activate G protein coupled receptors (GPCRs) that cause calcium release from intracellular stores while other stimuli depolarize taste cells to cause calcium influx through voltage-gated calcium channels (VGCCs). While the signaling mechanisms that initiate calcium signals have been described in taste cells, the calcium clearance mechanisms (CCMs) that contribute to the termination of these signals have not been identified. In this study, we used calcium imaging to define the role of sodium-calcium exchangers (NCXs) in the termination of evoked calcium responses. We found that NCXs regulate the calcium signals that rely on calcium influx at the plasma membrane but do not significantly contribute to the calcium signals that depend on calcium release from internal stores. Our data indicate that this selective regulation of calcium signals by NCXs is due primarily to their location in the cell rather than to the differences in cytosolic calcium loads. This is the first report to define the physiological role for any of the CCMs utilized by taste cells to regulate their evoked calcium responses.

scholarly journals Mechanism of inhibitory action of TMB-8 [8-(NN-diethylamino)octyl-3,4,5-trimethoxybenzoate] on aldosterone secretion in adrenal glomerulosa cells

1985 ◽  
Vol 232 (1) ◽  
pp. 87-92 ◽  
Author(s):  
I Kojima ◽  
K Kojima ◽  
H Rasmussen
Keyword(s):  
Protein Kinase C ◽  
Angiotensin Ii ◽  
Protein Kinase ◽  
Calcium Release ◽  
Calcium Influx ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Aldosterone Secretion ◽  
Kinase C ◽  
Glomerulosa Cells

The mechanism of 8-(NN-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) action was evaluated in isolated adrenal glomerulosa cells. TMB-8 inhibits both angiotensin II- and K+-stimulated aldosterone secretion in a dose-dependent manner. The ID50 for angiotensin II- and K+-stimulated aldosterone secretion is 46 and 28 microM, respectively. In spite of the fact that 100 microM-TMB-8 inhibits angiotensin II-stimulated aldosterone secretion almost completely, TMB-8 (100 microM) does not inhibit angiotensin II-induced 45Ca2+ efflux from prelabelled cells nor does it affect inositol 1,4,5-trisphosphate-induced calcium release from non-mitochondrial pool(s) in saponin-permeabilized cells. TMB-8 has no inhibitory effect on A23187-induced aldosterone secretion, but 12-O-tetradecanoylphorbol 13-acetate-induced aldosterone secretion is completely abolished. TMB-8 effectively inhibits both angiotensin II- and K+-induced increases in calcium influx but has no effect on A23187-induced calcium influx. TMB-8 inhibits the activity of protein kinase C dose-dependently. These results indicate that TMB-8 inhibits aldosterone secretion without inhibiting mobilization of calcium from an intracellular pool. The inhibitory effect of TMB-8 is due largely to an inhibition of plasma membrane calcium influx, but this drug also inhibits the activity of protein kinase C directly.

scholarly journals Patterns of sarcomere activation, temperature dependence, and effect of ryanodine in chemically skinned cardiac fibers.

1986 ◽  
Vol 87 (6) ◽  
pp. 885-905 ◽  
Author(s):  
A Lundblad ◽  
H Gonzalez-Serratos ◽  
G Inesi ◽  
J Swanson ◽  
P Paolini
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Temperature Dependence ◽  
Calcium Release ◽  
Contractile Activity ◽  
The Other ◽  
Calcium Blockers ◽  
Calcium Accumulation ◽  
Contractile Activation

Functionally skinned and electrochemically shunted myocytes were prepared by perfusing rat hearts with collagenase in order to obtain a technically improved measurement of sarcomere dynamics and to evaluate the role of sarcoplasmic reticulum in situ with respect to contractile activation. In the presence of micromolar calcium, the myocytes exhibited phasic and propagated contraction waves beginning at one end and proceeding along the myocyte. Beating rates, the propagation velocity of the activation wave, and single sarcomere shortening and relaxation velocities were obtained by manual or automated analysis of 16-mm film recorded at 170 frames/s from a camera attached to a microscope that was equipped with a temperature-controlled stage. In parallel experiments, calcium accumulation by the sarcoplasmic reticulum of the myocytes in situ was measured by direct isotopic tracer methods. The frequency (10-38 min-1) of spontaneous contractions, the velocity (1.9-7.4 microns . s-1) of sarcomere shortening, and the velocity (1.7-6.8 microns . s-1) of sarcomere relaxation displayed identical temperature dependences (Q10 = 2.2), which are similar to that of the calcium pump of sarcoplasmic reticulum and are consistent with a rate limit imposed by enzyme-catalyzed mechanisms on all these parameters. On the other hand, the velocity (77-159 microns . s-1) of sequential sarcomere activation displayed a lower temperature dependence (Q10 = 1.5), which is consistent with a diffusion-limited and self-propagating release of calcium from one sarcomere to the other. The phasic contractile activity of the dissociated myocytes was inhibited by 10(-8)-10(6) M ryanodine (and not by myolemmal calcium blockers) under conditions in which calcium accumulation by sarcoplasmic reticulum in situ was demonstrated to proceed optimally. The effect of ryanodine is attributed to an interaction of this drug with sarcotubular structures, producing inhibition of calcium release from the sarcoplasmic reticulum. The consequent lack of sarcomere activation underlines the role of sarcoplasmic reticulum uptake and release in the phasic contractile activation of the electrochemically shunted myocytes.

scholarly journals Role of PKC in the Regulation of the Human Kidney Chloride Channel ClC-Ka

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Andrea Gerbino ◽  
Roberta De Zio ◽  
Daniela Russo ◽  
Luigi Milella ◽  
Serena Milano ◽  
...  
Keyword(s):  
Physiological Role ◽  
Renal Medulla ◽  
Human Kidney ◽  
Inhibitory Effect ◽  
Hek293 Cells ◽  
Whole Cell Patch Clamp ◽  
New Information ◽  
Intracellular Ca ◽  
Accessory Subunit

Abstract The physiological role of the renal ClC-Ka/ClC-K1 channels is to confer a high Cl- permeability to the thin Ascending Limb of Henle (tAL), which in turn is essential for establishing the high osmolarity of the renal medulla that drives water reabsorption from collecting ducts. Here, we investigated by whole-cell patch-clamp measurements on HEK293 cells co-expressing ClC-Ka (tagged with GFP) and the accessory subunit barttin (tagged with m-Cherry) the effect of a natural diuretic extract from roots of Dandelion (DRE), and other compounds activating PKC, such as ATP, on ClC-Ka activity and its membrane localization. Treatment with 400 µg/ml DRE significantly inhibited Cl- currents time-dependently within several minutes. Of note, the same effect on Cl- currents was obtained upon treatment with 100 µM ATP. Pretreatment of cells with either the intracellular Ca2+ chelator BAPTA-AM (30 μM) or the PKC inhibitor Calphostin C (100 nM) reduced the inhibitory effect of DRE. Conversely, 1 µM of phorbol meristate acetate (PMA), a specific PKC activator, mimicked the inhibitory effect of DRE on ClC-Ka. Finally, we found that pretreatment with 30 µM Heclin, an E3 ubiquitin ligase inhibitor, did not revert DRE-induced Cl- current inhibition. In agreement with this, live-cell confocal analysis showed that DRE treatment did not induce ClC-Ka internalization. In conclusion, we demonstrate for the first time that the activity of ClC-Ka in renal cells could be significantly inhibited by the activation of PKC elicited by classical maneuvers, such as activation of purinergic receptors, or by exposure to herbal extracts that activates a PKC-dependent pathway. Overall, we provide both new information regarding the regulation of ClC-Ka and a proof-of-concept study for the use of DRE as new diuretic.

A fluorometric study of the possible role of calcium in synchronizing substrate metabolism with contractile performance in rabbit papillary muscle

1983 ◽  
Vol 61 (10) ◽  
pp. 1185-1193 ◽  
Author(s):  
T. Russell Snow
Keyword(s):  
Papillary Muscle ◽  
Coupling Coefficient ◽  
Mechanical Performance ◽  
Contractile Activity ◽  
Tca Cycle ◽  
Isometric Tension ◽  
Rabbit Papillary Muscle ◽  
The Tca Cycle ◽  
Contractile Performance

Based on the hypothesis that Ca2+ plays an important role in coordinating the rates of substrate catabolism with those of mechanical power utilization, experiments were designed to answer two questions. First, to what extent do the separate Ca2+ pools (e.g., Na+–Ca2+ exchange, sarcoplasmic reticulum (SR)) contribute to this messenger Ca2+ pool; and second, are the three catabolic pathways (glycolysis, β-oxidation, and tricarboxylic acid (TCA)) equally sensitive to regulation by Ca2+. To answer these questions, an assessment of the dynamic relation between metabolism and mechanical performance in rabbit papillary muscle was employed which used the slope (coupling coefficient: Mc) of the linear relation between the maximum oxidation of NADH accompanying an increase in contractile activity and the product of the peak isometric tension times the stimulation rate. Except for ketones, changes in superfusate [Ca2+] significantly decreased the coupling coefficient, suggesting a greater sensitivity of metabolism to mechanical requirement. Studies using ouabain indicated that this response was not attributable to Na+–Ca2+ exchange. Experiments with theophylline yielded two important results. First, the redox response of the respiratory chain can be significantly influenced by the available substrate. Second, the glycogenoltic complex associated with the SR may play an important role in ensuring adequate supplies of reducing equivalents and therefore may be a prime site for coordinating metabolism with mechanical performance. The data also suggest that glycolysis and β-oxidation are more sensitive to regulation by messenger Ca24 than the TCA cycle.

The Sarcoplasmic Reticulum in Muscle Fatigue and Disease: Role of the Sarco(endo)plasmic Reticulum Ca2+-ATPase

2004 ◽  
Vol 29 (3) ◽  
pp. 308-329 ◽  
Author(s):  
A. Russell Tupling
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Contractile Activity ◽  
Muscle Relaxation ◽  
Low Frequency ◽  
Free Calcium ◽  
Cellular Mechanisms ◽  
Plasmic Reticulum ◽  
Low Frequency Fatigue

Skeletal muscles induced to contract repeatedly respond with a progressive loss in their ability to generate a target force or power. This condition is known simply as fatigue. Commonly, fatigue may persist for prolonged periods of time, particularly at low activation frequencies, which is called low-frequency fatigue. Failure to activate the contractile apparatus with the appropriate intracellular free calcium ([Ca2+]f) signal contributes to fatigue but the precise mechanisms involved are unknown. The sarcoplasmic reticulum (SR) is the major organelle in muscle that is responsible for the regulation of [Ca2+]f, and numerous studies have shown that SR function, both Ca2+ release and Ca2+ uptake, is impaired following fatiguing contractile activity. The major aim of this review is to provide insight into the various cellular mechanisms underlying the alterations in SR Ca2+ cycling and cytosolic [Ca2+]f that are associated both with the development of fatigue during repeated muscle contraction and with low-frequency or long-lasting fatigue. The primary focus will be on the role of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) in normal muscle function, fatigue, and disease. Key words: calcium release, calcium uptake, muscle relaxation, low-frequency fatigue, Brody disease

Avian shell gland contractility: interaction of PGF2 alpha and arginine vasotocin with Ca2+

1983 ◽  
Vol 244 (3) ◽  
pp. C150-C157 ◽  
Author(s):  
D. M. Olson ◽  
F. Hertelendy
Keyword(s):  
Longitudinal Muscle ◽  
Contractile Activity ◽  
Arginine Vasotocin ◽  
Channel Blockers ◽  
Shell Gland ◽  
Free Solution ◽  
Potassium Depolarization ◽  
Prostaglandin F2 Alpha ◽  
Tension Generation

The effects of prostaglandin F2 alpha (PGF2 alpha) and arginine vasotocin (AVT) on the isometric contractile activity of avian shell gland longitudinal muscle strips were studied in relation to the role of extracellular Ca2+. PGF2 alpha and AVT stimulated contractile tension in a dose-related manner. This was attenuated when either of the Ca2+ channel blockers verapamil or R33956 was added to the muscle chamber baths. Ca2+-free solution containing 1 mM ethyleneglycol-bis (beta-aminoethylether)-N,N'-tetraacetic acid completely prevented contraction in response to increasing doses of PGF2 alpha or AVT. Washing of the strips with Ca2+-free solution eliminated spontaneous contractile activity, but replenishment of CaCl2 to the medium (0.1-5.0 mM) restored it. Addition of PGF2 alpha to the Ca2+-free medium enhanced contractile tension during Ca2+ replenishment, whereas AVT had no effect on tension generation at low extracellular Ca2+ concentration (0.1-0.5 mM) but increased it at higher extracellular Ca2+ concentration (1.0-5.0 mM). PGF2 alpha stimulation was sensitive to extracellular Na+ concentration, whereas AVT-induced activity was not. Potassium depolarization (20 mM K) potentiated PGF2 alpha-stimulated activity, whereas the response to AVT was unaffected. At 127.5 mM K, AVT-stimulated activity was inhibited. PGF2 alpha-enhanced Ca2+-dependent tension generation was right shifted in a dose-related manner by AVT. These results suggest that extracellular Ca2+ is necessary for the full expression of PGF2 alpha- and AVT-stimulated muscle contraction and suggest that each agonist has a different mechanism of action.

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