Involvement of ceramide in inhibitory effect of IL-1 beta on L-type Ca2+ current in adult rat ventricular myocytes

1997 ◽  
Vol 272 (6) ◽  
pp. H2591-H2598 ◽  
Author(s):  
K. D. Schreur ◽  
S. Liu
Keyword(s):  
Ventricular Myocytes ◽  
Biological Effects ◽  
Inhibitory Effect ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Channel Current ◽  
Whole Cell Patch Clamp ◽  
Dependent Inhibition ◽  
Ceramide 1 ◽  
Ceramide Production

Interleukin (IL)-1 beta has previously been shown to decrease the L-type Ca2+ channel current (ICa,L). Because ceramide has been suggested to mediate many biological effects of IL-1 beta, we examined whether ceramide was involved in the IL-1 beta-induced suppression of ICa,L in adult rat ventricular myocytes. Exposure of myocytes to 5 ng/ml IL-1 beta elicited a 140% increase in ceramide production within 2 min, as measured with 32P phosphorylation. Whole cell patch-clamp techniques were used to measure ICa,L in myocytes internally dialyzed and externally perfused with Na(+)- and K(+)-free solutions. C2 ceramide (1 nM-1 microM), a membrane-permeable analog of ceramide, caused a concentration-dependent inhibition of ICa,L and increased the rate of ICa,L inactivation without altering its gating properties. An inactive ceramide analog failed to inhibit ICa,L. At submaximal concentrations, effects of C2 ceramide and IL-1 beta on ICa,L were additive and saturable. In the presence of a maximally effective concentration of IL-1 beta, C2 ceramide had no further effect on ICa,L. These results suggest that ceramide mediates IL-1 beta-induced suppression of cardiac ICa,L.

scholarly journals Inhibitory Effect of Cinobufagin on L-Type Ca2+Currents, Contractility, and Ca2+Homeostasis of Isolated Adult Rat Ventricular Myocytes

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Pinya Li ◽  
Qiongtao Song ◽  
Tao Liu ◽  
Zhonglin Wu ◽  
Xi Chu ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Concentration Dependent Manner ◽  
Cell Contractility ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Time To Peak ◽  
Whole Cell Patch Clamp

Cinobufagin (CBG), a major bioactive ingredient of the bufanolide steroid compounds of Chan Su, has been widely used to treat coronary heart disease. At present, the effect of CBG on the L-type Ca2+current (ICa-L) of ventricular myocytes remains undefined. The aim of the present study was to characterize the effect of CBG on intracellular Ca2+([Ca2+]i) handling and cell contractility in rat ventricular myocytes. CBG was investigated by determining its influence onICa-L, Ca2+transient, and contractility in rat ventricular myocytes using the whole-cell patch-clamp technique and video-based edge-detection and dual-excitation fluorescence photomultiplier systems. The dose of CBG (10−8 M) decreased the maximal inhibition of CBG by 47.93%. CBG reducedICa-Lin a concentration-dependent manner with an IC50of 4 × 10−10 M, upshifted the current-voltage curve ofICa-L, and shifted the activation and inactivation curves ofICa-Lleftward. Moreover, CBG diminished the amplitude of the cell shortening and Ca2+transients with a decrease in the time to peak (Tp) and the time to 50% of the baseline (Tr). CBG inhibited L-type Ca2+channels, and reduced[Ca2+]iand contractility in adult rat ventricular myocytes. These findings contribute to the understanding of the cardioprotective efficacy of CBG.

1,2-Dioctanoyl-sn-glycerol depresses cardiac L-type Ca2+ current: independent of protein kinase C activation

1996 ◽  
Vol 270 (2) ◽  
pp. C655-C662 ◽  
Author(s):  
K. D. Schreur ◽  
S. Liu
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Ventricular Myocytes ◽  
Inhibitory Effect ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Kinase C ◽  
Whole Cell Patch Clamp ◽  
Steady State Inactivation ◽  
Slope Factor

The present study examines the effect of 1,2-dioctanoyl-sn-glycerol (DiC8), a diacylglycerol analogue, on L-type Ca2+ current (ICa,L) in adult rat ventricular myocytes using whole cell patch-clamp techniques. Extracellular application of DiC8 (1-10 microM) resulted in a concentration-dependent inhibition of peak ICa,L (half-maximum inhibitory concentration = 2.2 microM). Results obtained from the current-voltage relationship showed that DiC8 decreased the slope conductance. In addition, DiC8 increased the rate of Ba2+ current inactivation and caused a hyperpolarizing shift in the steady-state inactivation by 6 mV and a decrease in the slope factor. The DiC8-induced inhibition of ICa,L was neither mimicked by activation of protein kinase C (PKC) with 100 nM phorbol 12-myristate 13-acetate (PMA) no prevented by inhibition of PKC with 30 microM H-7, 100 nM staurosporine, or 24-h pretreatment with PMA. These results suggest that in rat ventricular myocytes 1) 1,2-sn-diacylglycerol (DAG) inhibits ICa,L, possibly by facilitating channel inactivation and decreasing channel availability and 2) this inhibitory effect of DAG is independent of PKC activation.

Fluid pressure modulates L-type Ca2+ channel via enhancement of Ca2+-induced Ca2+ release in rat ventricular myocytes

2008 ◽  
Vol 294 (4) ◽  
pp. C966-C976 ◽  
Author(s):  
Sunwoo Lee ◽  
Joon-Chul Kim ◽  
Yuhua Li ◽  
Min-Jeong Son ◽  
Sun-Hee Woo
Keyword(s):  
Ventricular Myocytes ◽  
Fluid Pressure ◽  
Inhibitory Effect ◽  
Cellular Mechanism ◽  
Confocal Imaging ◽  
Rat Ventricular Myocytes ◽  
Whole Cell Patch Clamp ◽  
Current Voltage ◽  
Intracellular Ca ◽  
High Concentrations

This study examines whether fluid pressure (FP) modulates the L-type Ca2+ channel in cardiomyocytes and investigates the underlying cellular mechanism(s) involved. A flow of pressurized (∼16 dyn/cm2) fluid, identical to that bathing the myocytes, was applied onto single rat ventricular myocytes using a microperfusion method. The Ca2+ current ( ICa) and cytosolic Ca2+ signals were measured using a whole cell patch-clamp and confocal imaging, respectively. It was found that the FP reversibly suppressed ICa (by 25%) without altering the current-voltage relationships, and it accelerated the inactivation of ICa. The level of ICa suppression by FP depended on the level and duration of pressure. The Ba2+ current through the Ca2+ channel was only slightly decreased by the FP (5%), suggesting an indirect inhibition of the Ca2+ channel during FP stimulation. The cytosolic Ca2+ transients and the basal Ca2+ in field-stimulated ventricular myocytes were significantly increased by the FP. The effects of the FP on the ICa and on the Ca2+ transient were resistant to the stretch-activated channel inhibitors, GsMTx-4 and streptomycin. Dialysis of myocytes with high concentrations of BAPTA, the Ca2+ buffer, eliminated the FP-induced acceleration of ICa inactivation and reduced the inhibitory effect of the FP on ICa by ≈80%. Ryanodine and thapsigargin, abolishing sarcoplasmic reticulum Ca2+ release, eliminated the accelerating effect of FP on the ICa inactivation, and they reduced the inhibitory effect of FP on the ICa. These results suggest that the fluid pressure indirectly suppresses the Ca2+ channel by enhancing the Ca2+-induced intracellular Ca2+ release in rat ventricular myocytes.

Alpha 1b-adrenoceptor-mediated stimulation of Na-K pump current in adult rat ventricular myocytes

1993 ◽  
Vol 264 (4) ◽  
pp. H1315-H1318 ◽  
Author(s):  
A. P. Williamson ◽  
R. H. Kennedy ◽  
E. Seifen ◽  
J. P. Lindemann ◽  
J. R. Stimers
Keyword(s):  
Adrenergic Receptors ◽  
Ventricular Myocytes ◽  
Pump Current ◽  
Peak Effect ◽  
Patch Clamp Technique ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Whole Cell Patch Clamp ◽  
Dose Dependent ◽  
Stimulation Of

The purpose of this study was to determine if myocardial alpha 1a-and/or alpha 1b-adrenoceptors are involved in the increase in Na-K pump current (Ip) elicited by alpha 1-adrenergic agonists. Single rat ventricular myocytes were isolated by enzymatic disaggregation. The whole cell patch-clamp technique was used to examine dose-dependent effects of phenylephrine (PE) on holding current (Ih) and to determine whether observed actions were mediated via alpha 1a-or alpha 1b-adrenergic receptors. To minimize the contribution of transsar-colemmal currents other than Ip to Ih, membrane voltage was held constant -40 mV, and cells were maintained in a Ca-free perfusate containing 1 mM Ba and 0.1 mM Cd. All experiments were conducted in the presence of 3 microM nadolol. PE elicited dose-dependent increases in Ih, with a peak effect of 0.57 +/- 0.03 pA/pF observed at 30 microM. The response to PE was dose dependently inhibited by prazosin and chloroethylclonidine and was totally eliminated by 1 mM ouabain. When used at doses selective for the alpha 1a-subtype, WB4101 failed to significantly antagonize the action of PE. These data suggest that the observed alpha 1-adrenoceptor-mediated increase in Ih in isolated rat ventricular myocytes is the result of an increase in Ip effected via stimulation of alpha 1b-adrenergic receptors.

The effect of adrenomedullin on the L-type calcium current in myocytes from septic shock rats: signaling pathway

2007 ◽  
Vol 293 (5) ◽  
pp. H2888-H2893 ◽  
Author(s):  
Xiao-Hui Zhang ◽  
Gui-Rong Li ◽  
Jean-Pierre Bourreau
Keyword(s):  
Septic Shock ◽  
Calcium Current ◽  
Cardiac Tissue ◽  
Ventricular Myocytes ◽  
Adult Rats ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Mediated Effects ◽  
Whole Cell Patch Clamp ◽  
Cox 2

Adrenomedullin (ADM) is upregulated in cardiac tissue under various pathophysiological conditions, particularly in septic shock. The intracellular mechanisms involved in the effect of ADM on adult rat ventricular myocytes are still to be elucidated. Ventricular myocytes were isolated from adult rats 4 h after an intraperitoneal injection of lipopolysaccharide (LPS, 10 mg/kg). Membrane potential and L-type calcium current ( ICa,L) were determined using whole cell patch-clamp methods. APD in LPS group was significantly shorter than control values (time to 50% repolarization: LPS, 169 ± 2 ms; control, 257 ± 2 ms, P < 0.05; time to 90% repolarization: LPS, 220 ± 2 ms; control, 305 ± 2 ms, P < 0.05). ICa,L density was significantly reduced in myocytes from the LPS group (−3.2 ± 0.8 pA/pF) compared with that of control myocytes (−6.7 ± 0.3 pA/pF, P < 0.05). The ADM antagonist ADM-(22-52) reversed the shortened APD and abolished the reduction of ICa,L in shock myocytes. In myocytes from control rats, incubating with ADM for 1 h induced a marked decrease in peak ICa,L density. This effect was reversed by ADM-(22-52). The Gi protein inhibitor, pertussis toxin (PTX), the protein kinase A (PKA) inhibitor, KT-5720, and the specific cyclooxygenase 2 (COX-2) inhibitor, nimesulide, reversed the LPS-induced reduction in peak ICa,L. The results suggest a COX-2-involved PKA-dependent switch from Gs coupled to PTX-sensitive Gi coupling by ADM in adult rat ventricular myocytes. The present study delineates the intracellular pathways involved in ADM-mediated effects on ICa,L in adult rat ventricular myocytes and also suggests a role of ADM in sepsis.

G protein-mediated suppression of L-type Ca2+ current by interleukin-1 beta in cultured rat ventricular myocytes

1995 ◽  
Vol 268 (2) ◽  
pp. C339-C349 ◽  
Author(s):  
S. Liu ◽  
K. D. Schreur
Keyword(s):  
G Protein ◽  
Voltage Dependence ◽  
Ventricular Myocytes ◽  
Interleukin 1 ◽  
Signal Transduction Pathway ◽  
Interleukin 1 Beta ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Whole Cell Patch Clamp ◽  
Steady State Inactivation

The effect and possible signal transduction pathway of interleukin-1 beta (IL-1 beta) on the L-type Ca2+ current (ICa,L) in cultured adult rat ventricular myocytes were examined using whole cell patch-clamp techniques. When myocytes were internally dialyzed with a solution containing GTP, IL-1 beta caused a concentration-dependent decrease in the peak ICa,L (Ba2+ as the charge carrier). IL-1 beta did not significantly alter the voltage dependence of the peak ICa,L nor the steady-state inactivation and activation, but did slightly slow the rate of inactivation. In myocytes dialyzed with solutions without GTP or including guanosine 5'-O-(2-thiodiphosphate) to replace GTP, IL-1 beta had no effect on ICa,L. In contrast, when guanosine 5'-O-(3-thiotriphosphate) was used to replace GTP, the suppression of ICa,L induced by IL-1 beta remained. Preincubation of myocytes with pertussis toxin (PTX), which completely abolished the acetylcholine effect on isoproterenol-stimulated ICa,L, had no effect on the inhibitory action of IL-1 beta on ICa,L. We conclude that in cultured rat ventricular myocytes, IL-1 beta suppresses ICa,L via a PTX-insensitive G protein.

Inhibition of L-type Ca2+ channel current and negative inotropy induced by arachidonic acid in adult rat ventricular myocytes

2007 ◽  
Vol 293 (5) ◽  
pp. C1594-C1604 ◽  
Author(s):  
Shi J. Liu
Keyword(s):  
Arachidonic Acid ◽  
Ventricular Myocytes ◽  
Contractile Function ◽  
Nordihydroguaiaretic Acid ◽  
Patch Clamp Technique ◽  
Maximum Slope ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Channel Current ◽  
Voltage Dependent

We have previously shown an increase in arachidonic acid (AA) release in response to proinflammatory cytokines in adult rat ventricular myocytes (ARVM). AA is known to alter channel activities; however, its effects on cardiac L-type Ca2+ channel current ( ICa,L) and excitation-contraction coupling remain unclear. The present study examined effects of AA on ICa,L, using the whole cell patch-clamp technique, and on cell shortening (CS) and the Ca2+ transient of ARVM. ICa,L was monitored in myocytes held at −70 mV and internally equilibrated and externally perfused with Na+- and K+-free solutions. Exposure to AA caused a voltage-dependent block of ICa,L concentration dependently (IC50 8.5 μM). The AA-induced inhibition of ICa,L is consistent with its hyperpolarizing shift in the voltage-dependent properties and reduction in maximum slope conductance. In the presence of AA, BSA completely blocked the AA-induced suppression of ICa,L and CS. Intracellular load with AA had no effect on the current density but caused a small depolarizing shift in the ICa,L activation curve, suggesting a site-specific action of AA. Moreover, intracellular AA had no effect on the extracellular AA-induced decrease in ICa,L. Pretreatment with indomethacin, an inhibitor of cyclooxygenase, or addition of nordihydroguaiaretic acid, an inhibitor of lipoxygenase, had no effect on AA-induced changes in ICa,L. Furthermore, AA suppressed CS and Ca2+ transients of intact ARVM with no significant effect on SR function and myofilament Ca2+ sensitivity. Therefore, these results suggest that AA inhibits contractile function of ARVM, primarily due to its direct inhibition of ICa,L at an extracellular site.

Suppression of β-adrenergic responsiveness of L-type Ca2+ current by IL-1β in rat ventricular myocytes

1999 ◽  
Vol 276 (1) ◽  
pp. H141-H148 ◽  
Author(s):  
Shi J. Liu ◽  
Weiguo Zhou ◽  
Richard H. Kennedy
Keyword(s):  
Patch Clamp ◽  
Ventricular Myocytes ◽  
Adenylyl Cyclase Activity ◽  
Camp Content ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Camp Analog ◽  
Whole Cell Patch Clamp ◽  
Independent Mechanism ◽  
Cgp 12177

The possible mechanism by which interleukin-1β (IL-1β) affects β-adrenergic responsiveness of L-type Ca2+ current ( I Ca,L) was examined in adult rat ventricular myocytes by use of whole cell patch-clamp techniques. In the presence of isoproterenol (Iso), exposure for 3 min to IL-1β suppressed the Iso-activated I Ca,L. In the presence of IL-1β, the response of I Ca,L to Iso was decreased, and the EC50 for Iso stimulation was increased. However, IL-1β had no effect on [3H]CGP-12177 binding, displacement of [3H]CGP-12177 binding by Iso, or on basal and Iso-enhanced cAMP content. When I Ca,L was activated by extracellular application of forskolin or 8-(4-chlorophenylthio)-cAMP, a membrane-permeable cAMP analog, or by intracellular dialysis with cAMP, IL-1β had little effect on I Ca,L. In contrast, in the presence of cAMP, IL-1β still suppressed the Iso-enhanced I Ca,L. These results show that the IL-1β-induced decrease in β-adrenergic responsiveness of I Ca,L does not result from inhibition of β-adrenoceptor binding, adenylyl cyclase activity, or cAMP-mediated pathways, suggesting a cAMP-independent mechanism.

Effect of tetramethyl pyrazine on L-type calcium channel in rat ventricular myocytes

2001 ◽  
Vol 79 (7) ◽  
pp. 621-626 ◽  
Author(s):  
Lu-Yun Zou ◽  
Xue-Mei Hao ◽  
Guang-Qing Zhang ◽  
Mei Zhang ◽  
Ji-Hong Guo ◽  
...  
Keyword(s):  
Time Course ◽  
Ventricular Myocytes ◽  
Antagonistic Effect ◽  
Patch Clamp Technique ◽  
Inactivation Curve ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Whole Cell Patch Clamp ◽  
Steady State Inactivation ◽  
Ionic Mechanisms

To elucidate possible ionic mechanisms of antimyocardial ischemia and antiarrythmia of tetramethyl pyrazine (TP), we studied L-type Ca2+ currents (ICa.L) in adult rat ventricular myocytes using the whole-cell patch-clamp technique. The results showed: (i) under physiological conditions, 0.25 mmol/L TP decreased amplitude of ICa.L to 60.6% and this inhibition was increased with increasing concentration of TP. ID50 was 0.20 mmol/L. (ii) The Ca2+-antagonistic effect of TP was voltage-dependent. A marked negative shift of the steady-state inactivation curve was observed with long (10 s) conditioning prepulses, but not with short (350 ms) ones. (iii) The time course of inhibition during TP treatment was increased with an increase in drug concentration, and recovery from TP-induced inactivation of ICa.L was slower than in control cases. (iv) Tonic block and use-dependent block with TP treatment, which was induced by increasing the frequency of stimulation, occurred. We suggest that TP inhibits the ICa.L mainly by binding to inactivated Ca2+ channels. The high affinity of TP for the inactivated state of ICa.L may play an important role in developing therapies for pathological conditions.Key words: Tetramethyl pyrazine, L-type calcium current, rat ventricular myocytes.

PKC-independent inhibition of cardiac L-type Ca2+ channel current by phorbol esters

1996 ◽  
Vol 270 (2) ◽  
pp. H620-H627 ◽  
Author(s):  
T. Asai ◽  
L. M. Shuba ◽  
D. J. Pelzer ◽  
T. F. McDonald
Keyword(s):  
Protein Kinase C ◽  
Phorbol Esters ◽  
Ventricular Myocytes ◽  
Inhibitory Effect ◽  
Independent Action ◽  
Independent Manner ◽  
Channel Current ◽  
Kinase C ◽  
Channel Currents ◽  
Stimulation Of

Active and inactive phorbol esters were applied to guinea pig ventricular myocytes to study the responses of L-type Ca2+ (ICa,L) and L-type Na+ (INa,L) currents. Phorbol 12-myristate 13-acetate (PMA) (10-100 rM) never stimulated ICa,L or INa,L and frequently depressed them by 5-30% in a voltage-independent manner. However, the phorbol ester consistently activated delayed-rectifying K+ (IK) and Cl- currents. The inhibition of ICa,L occurred approximately 3 times faster than comonitored stimulation of IK, and ICa,L and INa,L were unaffected by two interventions that suppressed IK stimulation [pretreatment with 50 microM 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) and dialysis with pCa 11 versus standard pCa 9 solution]. Inactive phorbol esters 4 alpha-phorbol 12,13-didecanoate (alpha-PDD) and 4 alpha-phorbol had little effect on IK, but alpha-PDD had a PMA-like inhibitory effect on Ca2+ channel currents. We conclude that, unlike the stimulation of IK by PMA, inhibition of Ca2+ channel current by phorbol esters is a protein kinase C-independent action.

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