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*

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

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

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

Na+ -Ca2+ exchanger (NCX) transports Ca2+ coupled with Na+ across the plasma membrane in a bi-directional mode. Ca2+ flux via NCX mediates osteogenic processes, such as formation of extracellular matrix proteins and bone nodules. However, it is not clearly understood how the NCX regulates cellular Ca2+ movements in osteogenic processes. In this study, the role of NCX in modulating Ca2+ content of intracellular stores ([Ca2+](ER)) was investigated by measuring intracellular Ca2+ activity in isolated rat osteoblasts. Removal of extracellular Na+ elicited a transient increase of intracellular Ca2+ concentration ([Ca2+](i)). Pretreatment of antisense oligodeoxynucleotide (AS) against NCX depressed this transient Ca2+ rise and raised the basal level of [Ca2+](i). In AS-pretreated cells, the expression and activity of alkaline phosphatase (ALP), an osteogenic marker, were decreased. However, the cell viability was not affected by AS-pretreatment. Suppression of NCX activity by the AS-pretreatment decreased ATP-activated Ca2+ release from intracellular stores and significantly enhanced Ca2+ influx via store operated calcium influx (SOCI), compared to those of S-pretreated or control cells. These results strongly suggest that NCX has a regulatory role in cellular Ca2+ pathways in osteoblasts by modulating intracellular Ca2+ content.
Alkaline Phosphatase/metabolism ; Animals ; Calcium/*metabolism ; Cell Membrane/metabolism ; Cell Survival ; Cells, Cultured ; Cytoplasm/metabolism ; Endoplasmic Reticulum/metabolism ; Intracellular Space/metabolism ; Oligodeoxyribonucleotides, Antisense/pharmacology ; Osteoblasts/drug effects/*physiology ; Rats ; Signal Transduction ; Sodium/physiology ; Sodium-Calcium Exchanger/*physiology

Spinal α-motoneurons directly innervate skeletal muscles and function as the final common path for movement and behavior. The processes that determine the excitability of motoneurons are critical for the execution of motor behavior. In fact, it has been noted that spinal motoneurons receive various neuromodulatory inputs, especially monoaminergic one. However, the roles of histamine and hypothalamic histaminergic innervation on spinal motoneurons and the underlying ionic mechanisms are still largely unknown. In the present study, by using the method of intracellular recording on rat spinal slices, we found that activation of either H or H receptor potentiated repetitive firing behavior and increased the excitability of spinal α-motoneurons. Both of blockage of K channels and activation of Na-Ca exchangers were involved in the H receptor-mediated excitation on spinal motoneurons, whereas the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels were responsible for the H receptor-mediated excitation. The results suggest that, through switching functional status of ion channels and exchangers coupled to histamine receptors, histamine effectively biases the excitability of the spinal α-motoneurons. In this way, the hypothalamospinal histaminergic innervation may directly modulate final motor outputs and actively regulate spinal motor reflexes and motor execution.
Animals ; Histamine ; pharmacology ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ; metabolism ; Motor Neurons ; drug effects ; physiology ; Rats ; Receptors, Histamine H2 ; metabolism ; Sodium-Calcium Exchanger ; metabolism

OBJECTIVETo investigate the role of sodium-calcium exchanger (NCX) on ischemic preconditioning and pharmacological preconditioning.

METHODSCultured rat neonatal cardiomyocytes were randomly divided into 6 groups: (1) ischemia/reperfusion group (9 h ischemia followed by 1 h reperfusion, I/R), (2) ischemic preconditioning group (1.5 h ischemia/1 h reperfusion + I/R), (3) pharmacologic preconditioning group, adenosine (10 micromol/L) pretreated for 1 h + I/R, (4) calmodulin-dependent protein kinase II (CaMKII) inhibitor KN-93 (0.5 micromol/L for 0.5 h) + ischemic preconditioning group, (5) KN-93 + pharmacologic preconditioning group, (6) control group. The leakage of intracellular lactate dehydrogenase (LDH) in various groups was determined by biochemical autoanalyzer. Semi-quantitative RT-PCR was employed to measure the mRNA levels of sodium-calcium exchanger. Activity of sodium-calcium exchanger (Na(+)-dependent (45)Ca(2+) uptake) was measured by liquid scintillation counting.

RESULTS(1) Compared to the I/R group, the LDH leakages in both ischemic preconditioning group and pharmacologic preconditioning group were significantly reduced (P < 0.05) while significantly increased in the KN-93 + pharmacologic preconditioning group and the KN-93 + ischemic preconditioning group (P < 0.05). (2) The Na(+)-dependent (45)Ca(2+) uptake was significantly increased in the I/R group (P < 0.05) compared to control group and this increase could be significantly attenuated in ischemic preconditioning group and adenosine pretreatment group (P < 0.05). (3) The expression of NCX mRNA in I/R group was also significantly increased (P < 0.05) in the I/R group (P < 0.05) compared to control group and this increase could be significantly attenuated in ischemic preconditioning group and adenosine pretreatment group (P < 0.05), CaMKII inhibitor KN-93 significantly abolished these effects in preconditioning group (P < 0.05) and in adenosine pretreated group (P < 0.05).

CONCLUSIONNCX mediated the cardioprotective effects of ischemic preconditioning and pharmacological preconditioning in the neonatal cardiomyocytes I/R model.

Animals ; Calcium ; metabolism ; Calcium-Calmodulin-Dependent Protein Kinase Type 2 ; antagonists & inhibitors ; Cells, Cultured ; Ischemic Preconditioning, Myocardial ; L-Lactate Dehydrogenase ; metabolism ; Myocardial Reperfusion Injury ; metabolism ; therapy ; Myocytes, Cardiac ; metabolism ; RNA, Messenger ; metabolism ; Rats ; Rats, Sprague-Dawley ; Sodium-Calcium Exchanger ; metabolism

An increase in cytosolic free calcium has been shown to occur during ischemia in perfused hearts and plays a pivotal role in ischemia/reperfusion injury. The objective of this study was to investigate the contributions of Na(+)/H(+) exchange and Na(+)/Ca(2+) exchange to changes in intracellular calcium ([Ca(2+)](i)) during simulated ischemia and reperfusion in quiescent isolated rat cardiac myocytes. [Ca(2+)](i) was measured by laser confocal microscope using the fluorescent indicator Fluo 3 and expressed as the corrected intensity of Fluo 3 fluorescence. [Ca(2+)](i) increased to 140.3+/-13.0% (P<0.05 vs preischemic control 100%) after 5 min simulated ischemia, and remained at high level of 142.8+/-15.5% (P<0.05) after the following 15 min reperfusion. The increase in [Ca(2+)](i) during simulated ischemia and reperfusion was suppressed by 100 micromol/L amiloride (inhibitor of Na(+)/H(+) exchanger), 5 mmol/L NiCl2 (inhibitor of Na(+)/Ca(2+) exchanger) and calcium-free solution; [Ca(2+)](i) was 101.4+/-16.3%, 110.4+/-11.1% and 107.1+/-10.8%, respectively, after 5 min simulated ischemia, and 97.8+/-14.3%, 106.2+/-14.5% and 106.6+/-15.7%, respectively, after 15 min reperfusion. Compared with control cells, the amplitude of spontaneous calcium oscillation was lessened in cells treated with Ca-free perfusion and NiCl2 during reperfusion. In addition, no calcium oscillation was observed in cells pretreated with amiloride. These results suggest that Na(+)/H(+) exchange and Na(+)/Ca(2+) exchange are activated during simulated ischemia in isolated quiescent cardiac myocytes, leading to the elevation of [Ca(2+)](i) induced by simulated ischemia and reperfusion.
Amiloride ; pharmacology ; Animals ; Calcium ; metabolism ; Cell Hypoxia ; Heart Ventricles ; cytology ; Male ; Myocardial Ischemia ; metabolism ; physiopathology ; Myocardial Reperfusion Injury ; metabolism ; physiopathology ; Myocytes, Cardiac ; cytology ; metabolism ; Nickel ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Sodium-Calcium Exchanger ; antagonists & inhibitors ; Sodium-Hydrogen Exchangers ; antagonists & inhibitors