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OBJECTIVE@#To investigate the effect of ferulic acid, a natural compound, on pancreatic beta cell viability, Ca2+ channels, and insulin secretion.@*METHODS@#We studied the effects of ferulic acid on rat insulinoma cell line viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide viability assay. The whole-cell patch-clamp technique and enzyme-linked immunosorbent assay were also used to examine the action of ferulic acid on Ca2+ channels and insulin secretion, respectively.@*RESULTS@#Ferulic acid did not affect cell viability during exposures up to 72 h. The electrophysiological study demonstrated that ferulic acid rapidly and concentration-dependently increased L-type Ca2+ channel current, shifting its activation curve in the hyperpolarizing direction with a decreased slope factor, while the voltage dependence of inactivation was not affected. On the other hand, ferulic acid have no effect on T-type Ca2+ channels. Furthermore, ferulic acid significantly increased insulin secretion, an effect inhibited by nifedipine and Ca2+-free extracellular fluid, confirming that ferulic acid-induced insulin secretion in these cells was mediated by augmenting Ca2+ influx through L-type Ca2+ channel. Our data also suggest that this may be a direct, nongenomic action.@*CONCLUSION@#This is the first electrophysiological demonstration that acute ferulic acid treatment could increase L-type Ca2+ channel current in pancreatic β cells by enhancing its voltage dependence of activation, leading to insulin secretion.
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Rats , Animals , Insulin Secretion , Insulin/pharmacology , Insulin-Secreting Cells/metabolism , Coumaric Acids/metabolism , Calcium/metabolismABSTRACT
Background: Obesity is associated with many functional gastrointestinal disorders, such as gastrointestinal motility disorder. Previous studies showed that adipose tissue-derived adipokine visfatin (VF), which increased in obesity, might impair myometrial contractility and cause vascular smooth muscle relaxation. Aims: To investigate the effect of VF on contractility of colonic smooth muscle in rats and its underlying mechanism. Methods: Segments of distal colon from normal Sprague-Dawley (SD) rats were dissected into strips (0.3 cm × 0.8 cm), and the effect of VF on contractility of muscle strips was measured by biological signal collection system. In in vitro study, colonic smooth muscle cells (SMCs) from neonatal SD rats were cultured and treated with VF; phosphorylation of myoglobulin light chain (MLC) and expression of calcium channel protein Cav1.2 (α1 subunit) were assessed by Western blotting. Cultured in buffer solution with or without calcium, the acetylcholine-stimulated intracellular Ca2+ level in SMCs was detected by confocal laser scanning microscopy. Results: In muscle strip contractility assay, VF (200 ng/mL) significantly inhibited the contractility of colonic smooth muscle strip from normal adult rats (P<0.05). In cultured colonic SMCs, VF (200 ng/mL) down-regulated the calcium channel protein Cav1.2 expression and reduced the intracellular Ca2+ level and MLC phosphorylation (P<0.05). Conclusions: VF may down-regulate the expression of calcium channel protein Cav1.2 on the membrane of colonic SMCs and cause colonic dysmotility by interfering with Ca2+ signaling and smooth muscle contractility.
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Objective To explore the effects of L?type calcium channel (LTCC) α1C and β3 subunits on that magnesium inhibited thoracic aortic calcification induced by β?glycerophosphate (β?GP). Methods Vascular smooth muscle cells (VSMCs) and aortic rings from rat aortic were cultured, then divided into control group, high phosphorus group (10 mmol/L β?GP), magnesium group (10 mmol/L β?GP+3 mmol/L MgSO4) and 2?APB (an inhibitor of magnesium transporter) group (10 mmol/L β?GP+3 mmol/L MgSO4+0.1 mmol/L 2?APB). Calcium deposition of VSMCs and aortic rings were respectively measured by alizarin red staining and Von Kossa staining, meanwhile the quantification of their calcium was tested by OCPC. The mRNA expressions of Runx2, LTCCα1C andβ3 in VSMCs were detected by RT?PCR, and their protein expressions were detected by Western blotting. Intracellular calcium ion of VSMCs was tested by fluorescence probe and alkaline phosphatase (ALP)activity was measured by ELISA. The Runx2 expression of aortic rings was detected by immunohistochemistry. Results After VSMCs stimulated for 7 days, calcium, ALP, mRNA and protein expressions of LTCCα1C, LTCCβ3 and Runx2, and intracellular calcium ion in high phosphorus group were higher than those in control group (all P0.05). Conclusion Magnesium may down?regulate expressions of LTCCα1C andβ3 subunit, prevent calcium influx and then inhibit osteogenic differentiation so as to reduce β?glycerophosphate?induced VSMCs calcification.
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Objective To evaluate the role of calcium channel in the mechanism of the generation and maintenance of bursting firing of substantia nigra pars compacta (SNc) dopaminergic neurons in rats.Methods Using the patch clamp technique,we observed the firing pattern switching features after adding 10 μmol/L N-methyl-D-aspartic acid (NMDA),compared the changes of whole-calcium current and L-type calcium current with or without NMDA,and analyzed the correlation between the generation of burst firing and L-type calcium channel activation.Results After NMDA treatment,the firing pattern of SNc dopaminergic neurons changed to burst firing,which was compromised by a charastistic high plateau potential and series of action potential on it.The current density of L-type calcium current increased significantly after adding NMDA,which,from (2.86 ±0.26) pA/pF (n =28),significantly increased to (3.75 ± 0.18) pA/pF (n =34 ; t =7.52,P =0.002 8).The high plateau potential was almost abolished with the application of verapamil,a specific antagonist of L-type calcium channel.Consiusion NMDA could induce the firing pattern changed to burst firing in SNc dopaminergic neurons,while L-type calcium channel contributes to the process of generation and maintenance of burst firing.
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BACKGROUND:Calcium channel abnormalities can damage myocardium. Heroin can directly affect calcium ion channel, and alter myocardial structure. OBJECTIVE:To study the changes of heroin-induced myocardial ultrastructure, L-type calcium channel current and action potential of myocardial cel s after rat cardiac arrhythmia. METHODS:Sprague-Dawley rats were randomly divided into control group and model group. In the model group, rats were administered heroin at initial dose of 5 mg/kg?d. The daily dose escalation method was used (increasing dose:2.5 mg/kg?d) to replicate rat models of heroin addiction. At 20 days, models of heroin addiction were successful y established. At 30 days after increasing the dose, rat models of heroin addiction-induced arrhythmias were further established. RESULTS AND CONCLUSION:Compared with the control group, the electron microscopy demonstrated that myocardial structure changes mainly presented nuclear membrane shrinkage, nuclear condensation, nuclei became smal , chromatin assembled into blocks, mitochondria disordered and disappeared, sarcomeres disordered, focal fracture, and unclear myofilament in rat models of heroin addiction. Electric current-voltage curve of myocardial cel L-type calcium channel current showed the increasing trends. The 90%repolarization action potential was significantly shortened. These data indicated that heroin can directly lead to the pathological change of myocardial structure. Calcium channel current change is one of the main reasons for myocardial injury.
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Objective To observe the influence of Simvastatin on the ATP-sensitive K+Channels and L-type Ca2+ Channels in mouse pancreatic beta cell line MIN6.Methods MIN6 cells were divided into 0.05 ％ dimethyl sulfoxide (DMSO) group,normal control group and low-,middle-,high-concentration of Simvastatin treatment groups,that were cultured for 48 h with high-glucose DMEM containing 15％ fetal bovine serum plus 0.05％ dimethyl sulfoxide,0,2,5 and 10 μmol/Lsimvastatin,respectively.Whole-cell patch-clamp technology was used to record the currents of ATP-sensitive K+ channels and L-type Ca2+ channels in MIN6 cells.Results The mean potassium current density in normal external solution perfusion group was (92.81 ±4.10) pA/pF.Compared with normal external solution perfusion control group,2,5 and 10 μmol/L Simvastatin treatments markedly enhanced the current density of ATP-sensitive K+ Channels,reaching to (117.94 ± 3.67)pA/pF,(153.91±12.38) pA/pF,(307.01±6.40) pA/pF (all P＜0.01),respectively.The current density in L-type Ca2+ Channels was (-21.03 ± 0.55) pA/pF in glucose external solution group.Compared with glucose external solution group,the current density in 2,5 and 10 μmol/L Simvastatin treatment groups were decreased to (16.31±0.51) pA/pF,(-10.75±0.71) pA/pF,(-3.30±0.46) pA/pF (all P＜0.01),respectively.Conclusions Simvastatin inhibits insulin secretion and glycometabolism in mouse pancreatic beta cell line MIN6 via enhancing the current density of ATP-sensitive K+ Channels and inhibiting the current density of L-type Ca2+ Channels.
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Objective To investigate the effects of motilin on the voltage dependent potassium channel and L-type calcium channel currents in rat proximal colon smooth muscle cells (PCSM) and to explore its mechanism in increasing colonic motility.Methods PCSM were isolated by collagenase.The voltage dependent potassium channel transit outward current (IKA ) and delayed rectifier current (IKdr) and L-type calcium currents (ICa(L)) were measured by whole cell patch clamp technique.Groups were analyzed by paired t-test.Results There was no significant effect of motilin on IKA and IKdr.L-type calcium channel was dose-dependently activated by motilin from 0.5 × 105 mmol/L to 10.0 ×10-5 mmol/L.At 6 × 10-5 mmol/L motilin and under - 10,0 and 10 mV stimulating voltage,maximum current density increased by 154.61％,62.69％ and 21.02％ respectively and activation kinetics curve obviously left shifted.Half activation voltage decreased from (2.740±1.211) mV prior administration to ( - 25.290 ± 0.614) mV (t =8.534,P =0.007 ) and there was no significant difference in slope factor. Conclusions Motilin increases colonic smooth muscle contraction by promoting calcium influx. However the frequency of colonic smooth muscle contraction could not change with frequency of equilibrium potential and action potential of colonic smooth muscle.
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Dendroaspis natriuretic peptide (DNP), a new member of the natriuretic peptide family, is structurally similar to atrial, brain, and C-type natriuretic peptides. However, the effects of DNP on the cardiac function are poorly defined. In the present study, we examined the effect of DNP on the cardiac L-type Ca2+ channels in rabbit ventricular myocytes. DNP inhibited the L-type Ca2+ current (ICa,L) in a concentration dependent manner with a IC50 of 25.5 nM, which was blocked by an inhibitor of protein kinase G (PKG), KT5823 (1 microM). DNP did not affect the voltage dependence of activation and inactivation of ICa,L. The alpha1c subunit of cardiac L-type Ca2+ channel proteins was phosphorylated by the treatment of DNP (1 microM), which was completely blocked by KT5823 (1 microM). Finally, DNP also caused the shortening of action potential duration in rabbit ventricular tissue by 22.3 +/- 4.2% of the control (n = 6), which was completely blocked by KT5823 (1 microM). These results clearly indicate that DNP inhibits the L-type Ca2+ channel activity by phosphorylating the Ca2+ channel protein via PKG activation.
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Animals , Rabbits , Action Potentials/drug effects , Biological Transport/drug effects , Calcium/metabolism , Calcium Channels, L-Type/metabolism , Carbazoles/pharmacology , Cells, Cultured , Cyclic GMP-Dependent Protein Kinases/antagonists & inhibitors , Elapid Venoms/metabolism , Enzyme Activation , Heart , Heart Ventricles/drug effects , Myocytes, Cardiac/drug effects , Patch-Clamp Techniques , Peptides/metabolism , Phosphorylation/drug effectsABSTRACT
FUNDAMENTO: O tramadol é um analgésico de ação central cujo mecanismo de ação envolve a ativação de um receptor opioide. Anteriormente, mostramos que o tramadol e seus enantiômeros apresentavam um efeito inotrópico negativo sobre o músculo papilar no qual o (+)-enantiômero era mais potente que (-)- e (±)-tramadol. OBJETIVO: No presente trabalho, investigamos os efeitos do tramadol e seus enantiômeros na corrente de cálcio tipo L (I Ca-L). MÉTODOS: Os experimentos foram realizados em miócitos ventriculares isolados de ratos Wistar utilizando a técnica de patch-clamp com configuração de célula inteira. RESULTADOS: O tramadol (200 µM) reduziu a amplitude de pico do I Ca-L em potenciais de 0 a +50 mV. Em 0 mV, a I Ca-L foi reduzida em 33,7 ± 7,2 por cento. (+)- e (-)-tramadol (200 µM) produziram uma inibição semelhante da I Ca-L, na qual a amplitude do pico foi reduzida em 64,4 ± 2,8 por cento e 68,9 ± 5,8 por cento, respectivamente a 0 mV (P > 0,05). O tramadol, (+)- e (-)-tramadol mudaram a inativação de estado estacionário de I Ca-L para potenciais de membrana mais negativos. Além disso, tramadol e (+)-tramadol alteraram significativamente a curva de recuperação dependente de tempo da I Ca-L para a direita e reduziram a recuperação de I Ca-L da inativação. A constante de tempo foi aumentada de 175,6 ± 18,6 a 305,0 ± 32,9 ms (P < 0,01) para o tramadol e de 248,1 ± 28,1 ms para 359,0 ± 23,8 ms (P < 0,05) para o (+)-tramadol. O agonista do receptor µ-opioide (DAMGO) não tem nenhum efeito na I Ca-L. CONCLUSÃO: A inibição da I Ca-L induzida por tramadol e seus enantiômeros não teve relação com a ativação de receptores opioides e poderia explicar, pelo menos em parte, seu efeito inotrópico negativo cardíaco.
BACKGROUND: Tramadol is a centrally acting analgesic, whose mechanism of action involves opioid-receptor activation. Previously, we have shown that tramadol and its enantiomers had a negative inotropic effect on the papillary muscle in which the (+)-enantiomer is more potent than (-)- and (±)-tramadol. OBJECTIVE: In this study, we investigated the effects of tramadol and its enantiomers on L-type calcium current (I Ca-L). RESULTS: Tramadol (200 µM) reduced the peak amplitude of I Ca-L at potentials from 0 to +50 mV. At 0 mV, I Ca-L was reduced by 33.7 ± 7.2 percent. (+)- and (-)-tramadol (200 µM) produced a similar inhibition of I Ca-L, in which the peak amplitude was reduced by 64.4 ± 2.8 percent and 68.9 ± 5.8 percent, respectively at 0 mV (p > 0.05). Tramadol, (+)- and (-)-tramadol shifted the steady-state inactivation of I Ca-L to more negative membrane potentials. Also, tramadol and (+)-tramadol markedly shifted the time-dependent recovery curve of I Ca-L to the right and slowed down the recovery of I Ca-L from inactivation. The time constant was increased from 175.6 ± 18.6 to 305.0 ± 32.9 ms (p < 0.01) for tramadol and from 248.1 ± 28.1 ms to 359.0 ± 23.8 ms (p < 0.05) for (+)-tramadol. The agonist of µ-opioid receptor DAMGO had no effect on the I Ca-L. CONCLUSION: The inhibition of I Ca-L induced by tramadol and its enantiomers was unrelated to the activation of opioid receptors and could explain, at least in part, their negative cardiac inotropic effect.
Subject(s)
Animals , Male , Rats , Analgesics, Opioid/pharmacology , Calcium Channels, L-Type/drug effects , Myocardial Contraction/drug effects , Myocytes, Cardiac/drug effects , Papillary Muscles/drug effects , Tramadol/pharmacology , Analysis of Variance , Depression, Chemical , Models, Animal , Patch-Clamp Techniques , Rats, Wistar , Tramadol/analogs & derivativesABSTRACT
Objective To investigate the effects of calcitonin gene-related peptide (CGRP) combined with norepinephrine (NE) on L-type calcium current (LCa-l) in rat ventricular myocytes. Methods Ventricular myocytes were isolated from SD rats (weighing 260-280 g) by retrograde perfusion of the heart via the aorta with an enzyme-containing solution as previously described. Whole-cell patch-clamp recording was made using Axopatch 200B amplifier. The cells were perfused for 1 min with Tyrode solution containing CGRP 1 × 10-7 mol/L (group CGRP) , NE 1 × 10-6 mol/L (group NE), or CGRP 1 × 10-7 mol/L + NE 1 × 10-6 mol/L (group CN) and again washed with Tyrode solution. ICa-L was recorded 1 min before and 1 min after the cells were perfused and 1 min after the cells were washed. I-V curve of ICa-L was made after the cells were perfused with solution containing CGRP or NE alone. Results CGRP significantly inhibited the peak of ICa-L, while NE significantly promoted the peak of ICa-L(P < 0.05) . The peak of ICa-L was significantly decreased 1 min after the cells were perfused in group CGRP,while increased 1 min after the cells were perfused in group NE compared with group CN ( P < 0.05). CGRP made the I-V curve of ICa-L move up-ward, while NE made the I-V curve of ICa-L move down-ward. Conclusion CGRP can weaken the promotion of ICa-L induced by NE in rat ventricular myocytes.
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ObjectiveTo evaluate the effect of naloxone on L-type calcium current (ICa-L) in isolated rat ventricular myocytes.MethodsAdult SD rats of both sexes aged 8 weeks weighing 200-250 g were used in this study.Single cardiac ventricular myocytes were enzymatically isolated from SD rats.ICa-L was measured in ventricular myocytes and recorded using whole cell patch-clamp technique.Different concentrations (20 and 100 μg/ml) of naloxone were added to the cardiomyocytes.The effect of naloxone on ICa-L was evaluated.ResultsThe peak current of ICa-L Was inhibited by naloxone in a concentration-dependent manner.Naloxone had no significant effect on steady-state activation curve.ConclusionNaloxone inhibits the L-type calcium channel of ventricular myocytes and exerts negative effect on ventricular muscle function.
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Objective To observe the effect of amylin on the islet β-cells voltage-gated L-calcium channels in rats. Method Patch clamp technique was employed in the observation of the features and changes of electric current of islet β-cells voltage-gated L-calcium channels before and after using amylin. Results In the glucose environment of 5. 5 mmoL/L, the electric current of rat islet β-cells voltage-gated L-calcium channels was activated at-40 mV and reached the peak at about +20 mV, with a peak value of about-120 pA and the insulin secretion level was(0. 76±0. 12) μg/L. Under the stimulation of glucose of 16. 7 mmol/L, the peak current voltage moved to the left and increased up to-140 pA and the level of insulin secretion measured (1.78±0. 13) μg/L. Hatch islet β-cells in amylin at the concentrations of 0. 5, 1.0, 5.0 and 10.0 μmol/L, respectively. It was observed that in the 0. 5 μmol/L and 1.0 μmol/L groups,there was no remarkable change in the peak potential activation voltage, current, and insulin secretion volume in comparison with the control group. However, in the environment of 5.5 mmol/L glucose, the increase of activation voltage of the 5.0 and 10.0 μmol/L groups was-30 mV, with the peak current reduced to approximately-80 pA and-60 pA and the insulin secretion decreased to (0. 49±0. 11) μg/L and (0. 36±0. 12) μg/L respectively. Under the concentration of 16. 7 mmol/L glucose, the activation voltage increased from-40 mV up to-30 mV and the peak current reduced to-80 pA and-40 pA. In the meantime, the insulin secretion decreased respectively to (1.20±0. 13) μg/L and (0. 89±0. 14) μg/L, which is of significance. Conclusion The secretion of insulin is synchronized with the opening of the islet β-cells voltage-gated L-calcium channels at the stimulation of glucose. The amylin inhibition of the insulin secretion is also synchronized with the opening of islet β-cells voltage-gated L-calcium channels and it's in a positive concentration-dependent manner.
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Total aralosides of Aralia elata (Miq) Seem (TASAES) from Chinese traditional herb Longya Aralia chinensis L was found to improve cardiac function. The present study was to determine the protective effects of TASAES on diabetic cardiomyopathy, and the possible mechanisms. Therefore, a single dose of streptozotocin was used to induce diabetes in Wister rats. Diabetic rats were immediately treated with low, medium and high doses of TASAES at 4.9, 9.8 mg/kg and 19.6 mg/kg body weight by gavage, respectively, for eight weeks. Cardiac function was evaluated by in situ hemodynamic measurements, and patch clamp for the L-type Ca2+ channel current (ICa2+-L) and transient outward K+ channel current (Ito). Histopathological changes were observed under light and electron microscope. The expression of pro-fibrotic factor, connective tissue growth factor (CTGF) was monitored using immunohistochemistry staining. Compared with diabetic group, medium and high doses, but not low dose, of TASAES showed a significant protection against diabetes-induced cardiac dysfunction, shown by increased absolute value of left ventricular systolic pressure (LVSP) and maximum rates of pressure development (+/-dp/dt(max)), and enhanced amplitude of ICa2+-L (P < 0.05). Histological staining indicated a significant inhibition of diabetes-caused pathological changes and up-regulation of CTGF expression (P < 0.05). The results suggest that TASAES prevents diabetes-induced cardiac dysfunction and pathological damage through up-regulating ICa2+-L in cardiac cells and decreasing CTGF expression.
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Animals , Male , Rats , Aralia/chemistry , Calcium Channels, L-Type/physiology , Cardiomyopathies/drug therapy , Connective Tissue Growth Factor/metabolism , Diabetes Mellitus, Experimental/complications , Drugs, Chinese Herbal/chemistry , Heart/drug effects , Hemodynamics , Myocardium/pathology , Oleanolic Acid/analogs & derivatives , Patch-Clamp Techniques , Potassium Channels/physiology , Rats, Wistar , Saponins/therapeutic use , Treatment OutcomeABSTRACT
Angiotensin II (AngII) is a crucial hormone that affects vasoconstriction and exerts hypertrophic effects on vascular smooth muscle cells. Here, we showed that phosphatidylinositol 3-kinase-dependent calcium mobilization plays pivotal roles in AngII-induced vascular constriction. Stimulation of rat aortic vascular smooth muscle cell (RASMC)-embedded collagen gel with AngII rapidly induced contraction. AngII-induced collagen gel contraction was blocked by pretreatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor (LY294002) whereas ERK inhibitor (PD98059) was not effective. AngII-induced collagen gel contraction was significantly blocked by extracellular calcium depletion by EGTA or by nifedipine which is an L-type calcium channel blocker. In addition, AngII-induced calcium mobilization was also blocked by nifedipine and EGTA, whereas intracellular calcium store-depletion by thapsigargin was not effective. Finally, pretreatment of rat aortic ring with LY294002 and nifedipine significantly reduced AngII-induced constriction. Given these results, we suggest that PI3K-dependent activation of L-type calcium channels might be involved in AngII-induced vascular constriction.
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Animals , Rats , Phosphatidylinositol 3-Kinase/metabolism , Angiotensin II/metabolism , Aorta, Thoracic/drug effects , Calcium Channels, L-Type/drug effects , Muscle Contraction/drug effects , Muscle, Smooth, Vascular/drug effects , Rats, Sprague-Dawley , Signal Transduction/drug effects , Specific Pathogen-Free Organisms , Vasoconstriction/drug effectsABSTRACT
OBJECTIVE To understand what role of the L-type calcium channels play in the mechanism of salicylate-induced tinnitus. METHODS The effects of salicylate on L-type calcium channels in freshly dissociated inferior colliculus neurons of rats were studied using the whole-cell voltage clamp method. RESULTS Salicylate blocked L-type calcium channel current (ICa,L) in concentration-dependent manner. The half-blocking concentration of salicylate was 1.99 mmol/L. Salicylate did not affect the conductance-voltage curve and the steady-state activation curve of ICa,L, shifted the steady-state inactivation curve of ICa,L by about 8 mV in the hyperpolarizing direction, and delayed the recovery from inactivation of ICa,L. CONCLUSION Our results suggest that salicylate’s blocking of L-type calcium channels may contribute to salicylate-induced tinnitus by decreasing the release of ?-aminobutyric acid in the inferior colliculus.
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AIM To study the effect of genistein (GST), a protein tyrosine kinases inhibitor, on L-type calcium channel currents (Iba,L or Ica,L, dependent on permeating ion used) in freshly dispersed colon smooth muscle cells from guinea-pig. METHODS Single colon smooth muscle cells were enzymatically dissociated from guinea-pig. L-type calcium currents were measured by conventional whole-cell patch-clamp techniques. RESULTS The peak amplitudes of Iba,L elicited to 10 mV test potential from a holding potential of -80 mV, were reversibly and dose-dependently reduced by GST (10-100 μmol·L-1) with an IC50 value of (39.9±3.6)μmol·L-1. Bath application of GST shifted the steady-state inactivation curves of Iba,L in a hyperpolarized direction (about 10 mV, P＜0.01) without altering their slopes. The peak amplitudes of Iba,L were also inhibited but to a less extent by daidzein, an inactive analogue of GST. Sodium orthovanadate 1 mmol·L-1, a potent inhibitor of protein tyrosine phosphatases, blocked GST-induced inhibition of Ica,L. CONCLUSION GST can block L-type calcium channel activity in guinea-pig colon smooth muscle cells via tyrosine kinase pathway.
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0.05). Conclusions Oxytocin, misoprostol or nimodipine can induce or inhibit labor through regulating expressions of VDCC L ? 1 and VDCC L ? 2 mRNA in the rat uterine myometrium and it may not have an adverse effect on heart function of normal pregnant rats. VDCC L may be the common channel of labor induced by internal or external factors.
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Obiective To investigate the influence of rapid atrial pacing(RAP)on the expression of ?1c subunit of L-type calcium channel,and the protective effect of verapamil.Methods 30 rabbits were randomly assigned into RAP group and verapamil pre-conditioned group.Each group was further divided into 5 subgroups(n=3 for each subgroup).Electrode was embedded in the right atrium through right external jugular vein.Pacing was performed for 6h,12h,24h and 48h in different subgroups.No pacing in the sham operation group.For verapamil pre-conditioned group,the drug was intravenously administered(0.2mg/kg)30 minutes before the initiation of rapid atrial pacing.Right atrium tissue was harvested for determination of mRNA and protein expression of L-type calcium channel subunits by reverse transcription polymerase chain reaction(RT-PCR)and Western blot.Results The mRNA level of ?1c subunit started to be reduced 6h after rapid atrial pacing(RAP)and continued to decline as pacing continued,and the expression of protein was parallel with mRNA.Otherwise,the mRNA level of ?1c subunit started to decrease 24h after RAP and continued to decline while pacing continued,and the expression of protein paralleled with that of mRNA in verapamil pre-conditioned group.Verapamil can attenuate the down-regulation of L-type calcium channel of the atrium induced by RAP only at 24h after RAP,but the effect was less intent.Conclusion mRNA and protein expression level of L-type calcium channel subunits decreased after RAP,The calcium channel blocker verapamil can attenuate the down-regulation of L-type calcium channel of atrium induced by RAP resulting in a decrease or postponement of calcium overload in atrial myocytes,thus exerting protective effects on atrial electrical remodeling,but such effects vanished after prolonged pacing.
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【Objective】 The effect of pretreatment with Buyang Huanwu Decoction(BHD) on L-type calcium channels of cortical neurons in rats with global cerebral ischemia was observed,thus to explore the molecular therapeutic mechanism of BHD for cerebral ischemia as well as the pathogenic mechanism of Ca2+ message in ischemic injury of neurons.【Methods】SD rats were randomized into pseudo-operation group,model groups and BHD groups.And the model groups and BHD groups were divided into six groups according to the time points after reperfusion(2nd,12th,24th,48th and 72nd hour after reperfusion respectively).BHD groups received 0.64g/kg BHD by gastric infusion,bid,for 5 continuous days.Except the rats in pseudo-operation groups,the rats in other groups were induced global cerebral ischemia by modified Pulsinelli's four-vessel occlusion.Cerebral cortical neurons in rats were isolated promptly in 2nd,12th,24th,48th and 72nd hour after reperfusion.The recorded single-channel current was amplified by the EPC-9 patch-clamping amplifier,and then input into the computer by Pulse+Pulsefit.The analytical software TAC was used to detect the opening time and opening probability of the L-type Ca2+ channels in rats at different time points after reperfusion.【Results】In the model groups,the opening time of the L-type Ca2+ channels was prolonged after reperfusion as compared with that in the pseudo-operation group,and the opening probability of the L-type Ca2+ channels arrived at the peaks in 2nd and 24th hour after reperfusion.In BHD groups,the opening time in 72nd hour after reperfusion was decreased(P
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AIM: To study the effect of chronic hypoxia(CH) on the intracellular calcium([Ca~(2+)]i) in pulmonary artery smooth muscle cells(PASMCs) and the role of L-type calcium channel and calcium store. METHODS: The rat chronic hypoxia model was set up and intervene the PASMCs with normal PSS,calcium-free PSS,nifedipine,and heparine respectively.The resting [Ca~(2+)]i was determined with the Fura-2/AM calcium imaging technique.RESULTS:(1) The [Ca~(2+)]i in CH group in normal PSS was higher than that in control group in normal PSS(P