• The Korean Journal of Physiology
• /
• v.23 no.2
• /
• pp.237-252
• /
• 1989

Effect of a $Na^+$ gradient on $Ca^{2+}$ uptake was studied in isolated sarcolemmal vesicles of cat ileal longitudinal muscle. $Ca^{2+}$ uptake was markedly stimulated in the presence of an outwardly directed $Na^+$ gradient. External $Na^+$, monensin and A23187 abolished the $Na^+-dependent$ $Ca^{2+}$ uptake. Monovalent cations such as $K^+$, $Li^+$, $Rb^+$, $Cs^+$ and choline could not substitute for $Na^+$ in enhancement of $Ca^{2+}$ uptake. Divalent cations such as $Ba^{2+}$, $Sr^{2+}$, $Mn^{2+}$ and $Cd^{2+}$ but not $Mg^{2+}$ inhibited the $Na^+-dependent$ $Ca^{2+}$ uptake. Increase in external pH in the range of 6.0 to 8.0 stimulated the $Na^+-dependent$ $Ca^{2+}$ uptake. Amiloride inhibited the $Na^+-dependent$ $Ca^{2+}$ uptake at concentrations above 0.5 mM, whereas diltiazem or vanadate did not. The apparent Km of the $Na^+-dependent$ $Ca^{2+}$ uptake for $Ca^{2+}$ was 18.2 ${\mu}M$ and apparent Vmax was 689.7 pmole/mg protein/5 sec. Kinetic analysis of the $Na^+-dependent$ $Ca^{2+}$ uptake showed a noncompetitive interaction between internal $Na^+$ and external $Ca^{2+}$. The dependence of $Ca^{2+}$ uptake on internal $Na^+$ showed sigmoidal kinetics and Hill coefficient for internal $Na^+$ was 2.52. Inside positive membrane potential generated by imposing an inwardly directed $K^+$ gradient and valinomycin significantly stimulated the $Na^+-dependent$ $Ca^{2+}$ uptake. These results indicate that a $Na^+-Ca^{2+}$ exchange system exists in the sarcolemmal membranes isolated from cat ileal longitudinal muscle and it might operate as an electrogenic process.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.16 no.6
• /
• pp.267-272
• /
• 2006

A series of $Sr_{1-x}Ca_xGa_2S_4:Ce,Na$ phosphors have been synthesized by solid-state reaction. The photoluminescence and structural properties of $Sr_{1-x}Ca_xGa_2S_4:Ce,Na$ have been examined. The $Sr_{1-x}Ca_xGa_2S_4:Ce,Na$ phosphors have a strong absorption at 400 nm, which is the emission wavelength of a violet light emitting diode (LED). The emission peaks of $SrGa_2S_4:Ce,Na$are located at 448 nm and 485 nm. The partial replacement of Sr by Ca in $Sr_{1-x}Ca_xGa_2S_4:Ce,Na$ causes a red shift of emission wavelengths. The $Sr_{1-x}Ca_xGa_2S_4:Ce,Na$ can be used as blue emitting phosphors pumped by the violet LED for fabricating the multi-band white LED.

• The Korean Journal of Physiology
• /
• v.28 no.2
• /
• pp.159-167
• /
• 1994

The contraction of rabbit basilar artery was examined as a function of changes in the $Na^+$ electrochemical gradient in order to determine the contribution of $Na^+/Ca^{2+}$ exchange to the modulation of contractility. Ouabain $(10^{-5}\;M)$ or $K^+-free$ Tyrode solution caused an increase in tonic tension even in the presence of a $Ca^{2+}$ channel blocker $(10^{-6}\;M\;verapamil)$ and an ${\alpha}-receptor$ blocker $(10^{-5}\;M\;phentolamine)$. After treatment with ouabain $(10^{-5}\;M)$, contractions were augmented by reduction of external $Na^+$ concentration. The longer the treatment with ouabain $(10^{-5}\;M)$ was, the larger the amplitude of $Na^+-free$ contracture was. $Na^+-free$ contracture wag induced by either substitution of equimolar Tris for $Na^+$ or substitution of equimolar $Li^+\;for\;Na^+$. The competition between $Na^+\;and\;Ca^{2+}$ for the $Na^+/Ca^{2+}$ exchange carrier would exist, because it was observed that contractility was dependent on the $Na^+$ electrochemical gradient or the extracellular $Ca^{2+}$ concentration (2 mM, 4 mM). Ryanodine $(10^{-7}\;M)$, the blocker of intracellular $Ca^{2+}$ release from the sarcoplasmic reticulum, did not suppress the development of $Na^+-free$ contracture. The contractile response to norepinephrine $(10^{-6}\;M)$ was augmented by reducing the extracellular $Na^+$ concentration. The relaxation rate from caffeine-induced contraction was dependent on the extracellular $Na^+$ concentration (0 mM, 140 mM). From the above results, it could be suggested that $Na^+/Ca^{2+}$ exchange can move $Ca^{2+}$ either into or out of rabbit basilar arterial smooth muscle. $Ca^{2+}$ entry or extrusion is dependent upon the $Na^+$ electrochemical gradient. $Na^+/Ca^{2+}$ exchange plays a significant role in the regulation of contractility in rabbit basilar arterial smooth muscle.

• Archives of Pharmacal Research
• /
• v.10 no.2
• /
• pp.80-87
• /
• 1987

To get a better insight into the exxistence and the role of a Na-Ca exchange mechanism in smooth muscle, the effect of Na substitution with sucrose on tension development, cellular Ca uptake and $^{45}Ca$ efflux was investigated using isolated cat ileal longitudinal muscle strips. Experimental results were summarized as follows;1) Exposure of the cat ileal longitudinal muscle to Na-free solution induced a contraction, and the magnitude of the contraction increased after incubation of the muscle strips with ouabain ($2{\times10^{-}5}$M) for 1hr. 2) Cellular Ca uptake in Na-free solution increased with an increase in Na content of the Na-loading media, and a linear relationship existed between tissue Na content and cellular Ca uptake for 10 min 3) After tissues were equilibrated in PSS containing $^{45}Ca$ for 2hr, cellular Ca uptake decreased with rising the external Na concentration. 4)Removal of medium Na or inhibition of the Na-K pump decreased the rate of $^{45}Ca$ efflux. These results strongly suggested that Na substitution increases cellular Ca uptake and decreases the rate of $^{45}Ca$ efflux via a Na-Ca exchange mechanism.

• Journal of Bio-Environment Control
• /
• v.11 no.3
• /
• pp.127-132
• /
• 2002

Enhanced supply of $Ca^{2＋}$ as well as NO$_3$$^{[-10]}$ is known to restrict the uptake of the Na$^{＋}$ and Cl$^{[-10]}$ ion and ameliorate growth under saline conditions. This test was conducted to investigate the ameliorating effects of Ca(NO$_3$)$_2$ or CaCl$_2$ on the growth and yield of NaCl-stressed tomato plants grown in plastic pot filled with soil. All treatments except for the control were supplied with 80 mM NaCl fur two weeks after transporting. The saline solutions with nutrient were supplemented with either 0, 10 or 20 mM Ca(NO$_3$)$_2$ and either 0, 10 or 20 mM CaCl$_2$ during harvesting time from two weeks after transporting. Ca(NO$_3$)$_2$ or CaCl$_2$ application enhanced the growth such as plant height, fresh weight, dry weight, fruit number, and fruit weight, and yield of NaCl-stressed tomato, and also their effects increased greater as concentration of supplemented Ca(NO$_3$)$_2$ or CaCl$_2$increased. Yield increased in 20 mM Ca(NO$_3$)$_2$ compared with the others except fur the control. Photosynthetic rate in Ca treatments was lower than that of the control, but higher than that of NaCl treatment. Leaf chlorophyll content was higher in Ca treatments compared with the others, especially in younger leaf, while that was not affected by concentration of supplemented Ca. Ca(NO$_3$)$_2$ or CaCl$_2$ supply increased the $K^{＋}$ and $C^{2＋}$ concentration of tomato plants, whereas the Na$^{＋}$ transport to the leaves was inhibited. There was a strong increase in the $K^{＋}$/Na$^{＋}$ ratio in plants treated Ca(NO$_3$)$_2$, or CaCl$_2$. Cl$^{[-10]}$ content of plants was decreased by supplemental Ca(NO$_3$)$_2$ but Cl$^{[-10]}$ was increased in plants with CaCl$_2$compared with Ca(NO$_3$)$_2$. N concentration in plants of tomato increased with enhanced Ca(NO$_3$)$_2$ or CaCl$_2$supply, In conclusion, our study confirms the potential of Ca(NO$_3$)$_2$ or CaCl$_2$to alleviate NaCl-induced growth reductions in tomato.

• Archives of Pharmacal Research
• /
• v.12 no.2
• /
• pp.128-134
• /
• 1989

$Na^+-Ca^{2+}$ exchange process in sarcolemmal vesicles isolated from mesenteric arteries of Wistar-Kyoto normotensive(WKY) and spontaneously hypertensive rats(SHR) was investigated. The sarcolemmal fractions isolated after homogenization and sucrose density gradient centrifugation were enriched with 5'-nucleotidase and ouabain sensitive, $K^+-dependent$ phosphatase activities. When the vesicles were loaded with $Na^+$, a time dependent $Ca^{2+}$ uptake was observed. However, very little $Ca^{2+}$ uptake was observed when the vesicles were loaded with $K^+$, or $Ca^{2+}$ uptake of the $Na^+-loaded$ vesicles was carried out in high sodium medium so that there was no sodium gradient. When the vesicles loaded with $Ca^{2+}$ by $Na^+-Ca^{2+}$ exchange were diluted into potassium medium containing EGTA, $Ca^{2+}$ was rapidly released from the vesicles. $Na^+-dependent\;Ca^{2+}$ uptake was increased in SHR compared to WKY, but passive efflux of preaccumulated $Ca^{2+}$ from the vesicles was decreased in SHR. The data indicate that the membrane vesicles of rat mesenteric arteries exhibit $Na^+-Ca^{2+}$ exchange activity. It is also suggested that changes of this process in vascular smooth muscle cell membrane of SHR may be involved in higher intracellular $Ca^{2+}$ concentration and higher basal tone in SHR.

• Journal of Korean Biological Nursing Science
• /
• v.1 no.1
• /
• pp.25-41
• /
• 1999

Physiological activity of osteoblast including bone formation is known to be closely related to the increase of intracellular $Ca^{2+}$ activity($[Ca^{2+}]_i$) in osteoblast. $Ca^{2+}$ is an important intracellular messenger in diverse cellular functions, and regulation of its level is mediated by the transmembrane $Ca^{2+}$ movement via $Ca^{2+}$ channels, $Na^+-Ca^{2+}$ exchange, and by intracellular $Ca^{2+}$ movement through the intracellular stores. The purpose of this study is to investigate how the intracellular $Ca^{2+}$ is regulated in osteoblast-like cells(OLCs) by measuring $Ca^{2+}$ activity with cell imaging technique. OLCs were isolated from femur and tibia of neonatal rats, and cultured for 7 days. Cultured OLCs were loaded with a $Ca^{2+}$-sensitive fluorescent dye, Fura-2, and fluorescence images were monitored with a cooled CCD camera. The images were processed and analyzed with an image analyzing software. The results were as follows. (1) $[Ca^{2+}]_i$ of OLC decreased as the $Ca^{2+}$ concentration in the superfusing Tyrode solution was lowered. When $Na^+$ concentration in the superfusing solution was decreased, $[Ca^{2+}]_i$ increased.. These suggest that $Ca^{2+}$ flux occurs via the $Na^+-Ca^{2+}$ exchange mechanism. (2) When $Na^+$ in the superfusing solution was removed. a transient $Ca^{2+}$, increase($Ca^{2+}$ spike) was occasionally observed. However, $Ca^{2+}$ spike was not observed after adding 1 ${\mu}M$ thapsigargin. This implies that the generation of $Ca^{2+}$ spike is mediated by the release of $Ca^{2+}$ from endoplasmic reticulum(ER). (3) As the $Ca^{2+}$ concentration in the superfusing solution was raised, the frequency of 0mM $Na^+$-induced $Ca^{2+}$ spike increased, suggesting that $Ca^{2+}$-induced $Ca^{2+}$ release(CICR) mechanism exists. (4) After $[Ca^{2+}]_i$ was decreased with the superfusion of $Ca^{2+}$-free solution containing thapsigargin, the recovery of $[Ca^{2+}]_i$ with reperfusion of 2.5mM $Ca^{2+}$ solution transiently exceeded the control level, suggesting that the depletion of $Ca^{2+}$ in ER induces $Ca^{2+}$ influx from extracellular medium via store-operated $Ca^{2+}$ influx(SOCI) mechanism. (5) $[Ca^{2+}]_i$ was not affected by the superfusion of 25mM $K^+$ Tyrode solution. These results suggest that intracellular $Ca^{2+}$ activity in osteoblast is regulated by transmembrane $Ca^{2+}$ flux via $Na^+-Ca^{2+}$ exchange, $Ca^{2+}$ release from the internal store (ER) via $Ca^{2+}$-induced $Ca^{2+}$ release, and store-operated $Ca^{2+}$ influx across the cell membrane.

• Nuclear Engineering and Technology
• /
• v.49 no.8
• /
• pp.1778-1782
• /
• 2017

The interaction of $NpO^+_2$ with $Cl^-$ was studied using visible-near-infrared spectroscopy in $NaCl-Ca-Cl_2-NaClO_4$, $NaCl-NaClO_4$, and $CaCl_2-NaClO_4$ solutions with ionic strength (I) of 6M. The spectra of $NpO^+_2$ around 980 nm varied with $Cl^-$ concentration in the $NaCl-CaCl_2-NaClO_4$ and $NaCl-NaClO_4$ solutions at [$Cl^-$] ${\geq}3.5M$, but not in the $CaCl_2-NaClO_4$ solution. Assuming the 1:1 interaction between $NpO^+_2$ and $Cl^-$, the apparent equilibrium constants at I = 6M were evaluated. The presence of $Ca^{2+}$ was found to destabilize overall interaction between $NpO^+_2$ and $Cl^-$. The observations were consistent with the density functional theory calculation.

• Journal of the Korean Ceramic Society
• /
• v.35 no.10
• /
• pp.1007-1013
• /
• 1998

The samples of Bi2Sr2Ca1-xNaxCu2O8+y with various carrier concentration were synthesized by substituting Na for Ca ion. The superconducting properties hall coefficients and X-ray powder diffraction were measur-ed the sampled. Single phase samples were obtained for 0$\leq$x<0.3 of Bi2Sr2Ca1-xNaxCu2O8+y In the single phase the critical temperature. {{{{ { T}_{c } }} and carrier concentration increase with the increase of Na concentration pass through a maximum and then decreases. In the range of x$\geq$0.7 to the Na doped samples however we observed the metal-semiconductor transition. The c-axis seemed to decrease and a and b-axes increase with increasing Na concentration in the single phase. Decreasing of c-axis while increasing x is due to the smaller size of {{{{ {Na}^{+1 } }} ions to the {{{{ { Ca}^{+2 } }} ions. In the range of x>0.3 however the trend becomes ambiguous due to the inclusion of the 10K phase and impurity phase.

• The Korean Journal of Physiology
• /
• v.23 no.2
• /
• pp.291-299
• /
• 1989

Na and Ca effects on contracture were studied in order to estimate Na/Ca exchange ratio in the isolated atrial muscle of the rabbit. All experiments were performed in tris-buffered Tyrode solution which was being aerated with 100% $O_2\;and\;kept\;at\;37^{circ}C$. To load intracellular $Na^+,\;10{-6}M$ ouabain or K-free solution were used. Contractures were induced by brier exposure of atrial muscle to Tyrode solution containing various concentrations of Ca or of Na. The results obtained were as follows: 1 ) Increasing the extracellular Ca concentration, the amplitude of contracture also increased and was maximum at 8 mM Ca-Tyrode solution. 2) The relationship between extracellular Ca concentrations and relative amplitude of the contractures showed hyperbolic pattern. By using Hill plot, the line has the slope of 1 12 which means the number of Ca binding sites of the carrier in the cell membrane. 3) The amplitude of the contracture was maximum in 0 mM Na-Tyrode solution and decreased in dose dependent manner when the Na concentration increased. 4) When the relationship between extracellular Na concentrations and the amplitude of contractures was expressed as dose-response curve, the curve showed sigmoid pattern. The line with the slope of 2.82 was obtained by using Hill plot. 5) From above all the results, it is suggested that exchange ratio of Na and Ca via Na/ca exchange system in the atrial muscle of rabbit could be 3:1 approximately.