Humans ; Sodium-Calcium Exchanger ; Carrier Proteins ; Pain ; Calcium/metabolism*

The aim of the present paper was to study the role of sodium calcium exchanger (NCX) in the generation of action potentials (APs) in cardiomyocytes during early developmental stage (EDS). The precisely dated embryonic hearts of C57 mice were dissected and enzymatically dissociated to single cells. The changes of APs were recorded by whole-cell patch-clamp technique before and after administration of NCX specific blockers KB-R7943 (5 μmol/L) and SEA0400 (1 μmol/L). The results showed that, both KB-R7943 and SEA0400 had potent negative chronotropic effects on APs of pacemaker-like cells, while such effects were only observed in some ventricular-like cardiomyocytes. The negative chronotropic effect of KB-R7943 on ventricular-like cardiomyocytes was accompanied by shortening of AP duration (APD), whereas such an effect of SEA0400 was paralleled by decrease in velocity of diastolic depolarization (Vdd). From embryonic day 9.5 (E9.5) to E10.5, the negative chronotropic effects of KB-R7943 and SEA0400 on ventricular-like APs of embryonic cardiomyocytes gradually disappeared. These results suggest that, in the short-term development of early embryo, the function of NCX may experience developmental changes as evidenced by different roles of NCX in autorhythmicity and APs generation, indicating that NCX function varies with different conditions of cardiomyocytes.
Action Potentials ; Animals ; Calcium/metabolism* ; Mice ; Myocytes, Cardiac/metabolism* ; Sodium/metabolism* ; Sodium-Calcium Exchanger ; Thiourea/pharmacology*

BACKGROUND: Phenylephrine (PE) produces tonic contraction through involvement of various calcium channels such as store-operated calcium channels (SOCCs) and voltage-operated calcium channels (VOCCs). However, the relative contribution of each calcium channel to PE-induced contraction has not been investigated in isolated rat aorta of early acute myocardial infarction (AMI). METHODS: Endothelium-denuded rat aortic rings from rats 3 days after AMI or sham-operated (SHAM) rats were prepared in an organ chamber with Krebs-Ringer bicarbonate solution for isometric tension recording. We assessed the PE dose-response relationships in 2.5 mM calcium medium for both groups. The same procedure was repeated using rings pretreated with the SOCC inhibitor 2-aminoethoxydiphenyl borate, sarco/endoplasmic-reticulum calcium ATPase inhibitor thapsigargin (TG), diacyl glycerol lipase inhibitor RHC80267, and sodium-calcium exchanger inhibitor 3,4-dichlorobenzamil hydrochloride for 30 minutes before addition of calcium. When ongoing tonic contraction was sustained, dose-response curves to the VOCC inhibitor nifedipine were obtained to assess the relative contribution of each calcium channel under various conditions. RESULTS: The effect of SOCC induction with TG pretreatment on PE-induced contraction was significantly lower in the AMI group compared to the SHAM group. In addition, there were significant decreases in the sensitivity and efficacy of the VOCC inhibitor nifedipine on PE-induced contraction in the AMI group. CONCLUSIONS: Results suggest that the change of vascular reactivity of PE in rat aorta 3 days after AMI is characterized by a decreased contribution of L-type VOCCs. The enhanced VOCC-independent calcium entry mechanisms after AMI can be mediated by enhanced capacitative calcium entry through the activation of SOCCs.
Animals ; Aorta* ; Calcium Channels* ; Calcium* ; Calcium-Transporting ATPases ; Glycerol ; Lipase ; Myocardial Infarction* ; Nifedipine ; Phenylephrine ; Rats* ; Sodium-Calcium Exchanger ; Thapsigargin

Sodium calcium exchanger (NCX), which is widely expressed in the plasma membrane, mitochondrial membrane and secretory vesicles in diverse kinds of cells, belongs to a type of cation translocators. NCX works in two modes, the forward mode and reverse mode, to regulate the intracellular Ca(2+) concentration bi-directionally. In the forward mode, NCX carries Ca(2+) out of the cell against its electrochemical gradients coupled to the influx of Na(+) down its electrochemical gradients; alternatively, Ca(2+) enters through the reverse mode of NCX, and Na(+) is carried out of the cell. Exactly through the two-way modes, NCX can regulate intracellular Ca(2+) concentration fleetly and accurately, and plays a critical role in a series of physiological processes including intracellular signal transduction, growth and development of cells, excitation and its coupled functions of excitable cells. NCX are acknowledged to be involved in myofiber contraction, neurotransmission, migration and differentiation of neurogliocyte, activation of immune cells, secretion of cytokines and hormones etc. Moreover, abnormal activation of the reverse mode of NCX plays a vital role in many pathological processes including cell apoptosis, ischemia-reperfusion injury, insulin secretion, tumor etc. Here we reviewed the research status about the NCX's participation in some physiological and pathophysiological processes, so as to provide comprehensive understanding about its functions.
Animals ; Apoptosis ; Calcium ; physiology ; Humans ; Ion Transport ; Reperfusion Injury ; physiopathology ; Signal Transduction ; Sodium ; physiology ; Sodium-Calcium Exchanger ; physiology

OBJECTIVETo investigate the expression of Na(+)/Ca(2+) exchanger 1 (NCX1) channel protein in human odontoblasts (OD) and nervous tissue of dental pulp.

METHODSTwenty intact and healthy third molars extracted for orthodontic purpose were collected. The OD layer and nervous tissue were determined by dentin sialophosphoproteins (DSPP) antibody staining and modified Bielschowsky silver staining respectivelly. The immunohistochemical method was used to detect the expressions of NCX1 protein in human dental pulp tissue. The difference of expression of NCX1 in human OD at different part of dental pulp was statistically analyzed using Image Pro Plus and SPSS software.

RESULTSNCX1 channel protein was mainly expressed on the cell body of OD, and nervous tissue of dental pulp. The expression level of NCX1 on the OD of crown pulp was higher (A = 0.146 ± 0.021) than that on the upper part of root pulp (A = 0.120 ± 0.034), but the expression difference was not significant (P > 0.05).

CONCLUSIONSNCX1 channel protein was expressed on human OD and nervous tissue in dental pulp.

Dental Pulp ; innervation ; metabolism ; Dentin ; chemistry ; Humans ; Molar ; Odontoblasts ; metabolism ; Sodium-Calcium Exchanger ; metabolism ; Tooth Crown

The present study was aimed to investigate the positive inotropic mechanism of carbachol (CCh) on rat ventricular myocytes. The effects of CCh on L-type calcium current (I(Ca,L)) and Na(+)/Ca(2+) exchange current (I(Na/Ca)) were investigated in isolated rat ventricular myocytes. After loading myocytes with Fura-2/AM, electrically triggered Ca(2+) transient and cell shortening in single myocyte were measured simultaneously using ion imaging system with charge-coupled device (CCD) camera. CCh (100 mumol/L) increased I(Na/Ca) in forward mode from (1.18 +/- 0.57) pA/pF in the control group to (1.65 +/- 0.52) pA/pF (P<0.01) and that in reverse mode from (1.11 +/- 0.49) pA/pF in the control group to (1.53 +/- 0.52) pA/pF (P<0.01), respectively. CCh had no effect on I(Ca,L). The stimulatory effect of CCh on I(Na/Ca) was blocked by application of atropine, a non-selective M muscarinic receptor antagonist, and methoctramine, a selective M(2) muscarinic receptor antagonist. CCh (100 mumol/L) increased cell shortening from (3.00 +/- 0.67) mum in the control group to (3.55 +/- 1.21) mum. Ca(2+) transient was also increased from 203.8 +/- 50.0 in the control group to 234.8 +/- 64.3 in 100 mumol/L CCh group. KB-R7943, a selective inhibitor of reverse mode Na(+)/Ca(2+) exchange, did not change the baseline level of cell shortening and Ca(2+) transient, while completely abolished CCh-induced increments of both Ca(2+) transient and cell shortening. CCh increased cell shortening and Ca(2+) transient in the presence of nicardipine, indicating that the positive inotropic effect of CCh was through activation of Na(+)/Ca(2+) exchange. Calcium sensitivity was not changed by CCh. Both atropine and methoctramine abolished the positive inotropic effects of CCh, demonstrating that CCh induced positive inotropism via the M(2) muscarinic receptor. The results suggest that CCh increases cell contraction and Ca(2+) transient in rat ventricular myocytes. This positive inotropic effect of CCh is through activation of reverse mode Na(+)/Ca(2+) exchange, and M(2) receptors are involved in mediating CCh-induced contraction.
Animals ; Calcium ; Carbachol ; pharmacology ; Heart Ventricles ; Male ; Myocardial Contraction ; Myocytes, Cardiac ; drug effects ; Rats ; Receptor, Muscarinic M2 ; Receptors, Muscarinic ; drug effects ; Sodium ; Sodium-Calcium Exchanger ; Thiourea ; analogs & derivatives

Ischemia-reperfusion injury (IRI) has been recognized as a serious problem for therapy of cardiovascular diseases. Calcium regulation appears to be an important issue in the study of IRI. This article reviews calcium regulation in myocardial and vascular IRI, including the calcium overload and calcium sensitivity in IRI. This review is focused on the key players in Ca(2+) handling in IRI, including membrane damage resulting in increase in Ca(2+) influx, reverse-mode of Na(+)-Ca(2+) exchangers leading to increased Ca(2+) entry, the decreased activity of sarcoplasmic reticulum (SR) Ca(2+)-ATPase causing SR Ca(2+) uptake dysfunction, and increased activity of Rho kinase. These key players in Ca(2+) homeostasis will provide promising strategies and potential targets for therapy of cardiovascular IRI.
Animals ; Calcium ; metabolism ; Heart ; physiopathology ; Homeostasis ; Humans ; Myocardial Reperfusion Injury ; metabolism ; Myocardium ; Sarcoplasmic Reticulum ; metabolism ; Sarcoplasmic Reticulum Calcium-Transporting ATPases ; metabolism ; Sodium-Calcium Exchanger ; metabolism

Transient myocardial ischemia during cardiac surgery causes a loss of energy sources, contractile depression, and accumulation of metabolites and H+ ion resulting in intracellular acidosis. The reperfusion following ischemic cardioplegia recovers intracellular pH, activates Na+-H+ exchange and Na+-Ca2+ exchange transports and consequently produces Ca2+ overload, which yields cell death. Among the various Ca2+ entry pathways, the Na+-Ca2+ exchanger is known to play one of the major roles during the ischemia/reperfusion of cardioplegia. Consequently, information on the changes in intracellular Ca2+ activities of human cardiac myocytes via the Na+-Ca2+ exchanger is imperative despite previous measurements of Ca2+ current of human single myocytes. In this study, human single myocytes were isolated from the cardiac tissues obtained during open-heart surgery and intracellular Ca2+ activity was measured with cellular imaging techniques employing fluorescent dyes. We report that the Na+-Ca2+ exchanger of adult cardiac myocytes is more susceptible to hypoxic insult than that of young patients.
Adult ; Anoxia/*metabolism ; Calcium/*metabolism ; Child ; Child, Preschool ; Female ; Human ; Hydrogen-Ion Concentration ; Infant ; Male ; Middle Age ; Sodium-Calcium Exchanger/*physiology

AIMTo study and compare the excitation-contraction coupling triggered by L-type calcium current and by reverse-mode Na/Ca exchange during depolarizing steps in single guinea-pig ventricular myocytes.

METHODSWhole-cell membrane-potential, membrane-current and cell-shortening data were simultaneously acquired during whole-cell voltage clamp protocols. Voltage clamp pulses elicited ICa(L) at + 10 mV, + 50 mV, + 100 mV and evoked contractions in myocytes superfused with Tyrode's solution at 35 degrees C.

RESULTSThe greater the inhibition of I(Ca(L)), the more likely contractions would be abolished at +10 mV test potential. There was a correlation between them. At potential positive to + 50 mV, contractions were partially suppressed by Nif 100 micromol/L or Nif 30 micromol/L plus Cd2+30 micromol/L. The residual contraction was significantly delayed in onset. At +100 mV test potential, contractions were delayed in onset compare to + 50 mV and resistant to Nif 100 micromol/L or Nif 30 micromol/L plus Cd2+30 micromol/L. The residual contraction was completely blocked by Ni2+ at + 50 mV and + 100 mV.

CONCLUSIONSI(Ca(L)) is the major trigger for excitation-contraction coupling. Na/Ca exchange modulates excitation-contraction coupling as both reverse and forward mode.

Animals ; Calcium ; metabolism ; Calcium Channels, L-Type ; metabolism ; Cell Line ; Guinea Pigs ; Heart Ventricles ; cytology ; Myocardial Contraction ; physiology ; Myocytes, Cardiac ; cytology ; metabolism ; physiology ; Patch-Clamp Techniques ; Sodium ; metabolism ; Sodium-Calcium Exchanger ; physiology

BACKGROUNDNa + /Ca 2+ exchanger (NCX) plays a crucial role in pentylenetetrazol-induced convulsion. However, it is unclear whether NCX is critically involved in hyperthermia-induced convulsion. In this study, we examined the potential changes in NCX3 in the hippocampus and cerebrocortex of rats with hyperthermia-induced convulsion.

METHODSTwenty-one Sprague Dawley rats were randomly assigned to control group, convulsion-prone group and convulsion-resistant group (n = 7 in each group). Whole-cell patch-clamp method was used to record NCX currents. Both the Western blotting analysis and immunofluorescence labeling techniques were used to examine the expression of NCX3.

RESULTSNCX currents were decreased in rats after febrile convulsion. Compared to the control group, NCX3 expression was decreased by about 40% and 50% in the hippocampus and cerebrocortex of convulsion-prone rats, respectively. Furthermore, the extent of reduction in NCX3 expression seemed to correlate with the number of seizures.

CONCLUSIONSThere is a significant reduction in NCX3 expression in rats with febrile convulsions. Our findings also indicate a potential link between NCX3 expression, febrile convulsion in early childhood, and adult onset of epilepsy.

Animals ; Cerebral Cortex ; metabolism ; Down-Regulation ; Female ; Fever ; complications ; Hippocampus ; metabolism ; Pregnancy ; Rats ; Rats, Sprague-Dawley ; Seizures ; etiology ; metabolism ; Sodium-Calcium Exchanger ; metabolism