Role of Na⁺Ca²⁺ Exchange in the Control of Contractility in Rabbit Basilar Arterial Smooth Muscle

Kim Eui-Yong,Han Jin 대한생리학회 1994 대한생리학회지 Vol.28 No.2

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⁺/Ca²⁺ 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 Ca²⁺ channel blocker (10^-6 M verapamil) and an α-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 Ca²⁺ for the Na⁺/Ca²⁺ exchange carrier would exist, because it was observed that contractility was dependent on the Na⁺ electrochemical gradient or the extracellular Ca²⁺ concentration (2 mM, 4 mM). Ryanodine (10^-7 M), the blocker of intracellular Ca²⁺ 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⁺/Ca²⁺ exchange can move Ca²⁺ either into or out of rabbit basilar arterial smooth muscle. Ca²⁺ entry or extrusion is dependent upon the Na⁺ electrochemical gradient. Na⁺/Ca²⁺ exchange plays a significant role in the regulation of contractility in rabbit basilar arterial smooth muscle.

Role of $Na^+/Ca^{2+}$ Exchange in the Control of Contractility in Rabbit Basilar Arterial Smooth Muscle

Kim, Eui-Yong,Han, Jin The Korean Physiological Society 1994 대한생리학회지 Vol.28 No.2

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.

Inhibitors of Na^(+)/Ca^(2+) Exchanger Prevent Oxidant-Induced Intracellular Ca^(2+) Increase and Apoptosis in a Human Hepatoma Cell Line

KIM, JUNG AE,KANG, YOIUNG SHIN,LEE, SUN HEE,LEE, YONG SOO 영남대학교 약품개발연구소 2001 영남대학교 약품개발연구소 연구업적집 Vol.11 No.-

Oxidative stress appears to be implicated in the pathogenesis of various diseases including hepatotoxicity. Although intracellular Ca^(2+) signals have been suggested to play a role in the oxidative damage of hepatocytes, the sources and effects of oxidant-induced intracellular Ca^(2+) increases are currently debatable. Thus, in this study we investigated the exact source and mechanism of oxidant-investigated the exact source and mechanism of oxidant-induced liver cell damage using HepG2 human hepatoma cells as a model liver cellular system. Treatment with 200 ㎛ of tert-butyl hydroperoxide (tBOOH) induced a sustained increase in level of intracellular reactve oxygen intermediates (ROI) and apoptosis, assessed by 2,'7' -dichlordfluorescein fluorescence and flow cytometry. respectively. Antioxidants, N-acetyl cysteine (NAC) or N,N' -diphenyl-pphenylenediamine significantly inhibited both the ROI generation and apoptosis. In addition, tBOOH induced a slow and sustained increase in intracellular Ca^(2+) concentration, which was completely prevented by the concentration. An intracellular Ca^(2+) chelator, bis-(o-aminophenoxy)-ethene-N,N,N',N' -tetraacetic acid/cetoxymethyl ester significantly suppressed the tBOOH-induced apoptosis. These results imply that activation of an intracellular Ca^(2+) signal triggered by increased ROI may mediate the tBOOH-induced apoptosis. Both intracellular Ca^(2+) increase and induction of apoptosis were significantly inhibited by an extracellular Ca^(2+) chelator or Na^(-)/Ca^(2+) exchanger blockers (bepridil and benzamil), whereas neither Ca^(2+) channel antagonists (verapamil and nifedipine) nor a nonselective cation channel blocker (flufenemic acid) had an effect. These results suggest that tBOOH may increase intracellular Ca^(2+) through the activation of reverse mode of Na^(+)/Ca^(2+) exchanger. However, tBOOH decreased intracellular Na^(+) concentration, which was completely prevented by NAC. These results indicate that ROI generated by tBOOH may increase intracellular Ca^(2+) concentration by direct activation of the reverse mode of Na^(-)/Ca^(2+) exchanger, rather than indirect elevation of intracellular Na^(+) levels. Taken together, these results suggest that the oxidant, tBOOH induced apoptosis in human HepG2 cells and that intracellular Ca^(2+) may mediate this action of tBOOH. These results further suggest that Na^(+)/Ca^(@) exchanger may be a target for the management of oxidative hepatiotoxicity.

골아세포내 Ca^(2+) 활성도의 조절기전

박미정 대한기초간호자연과학회 1999 Journal of korean biological nursing science Vol.1 No.1

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 μM 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.

A Study on the $Na^+/Ca^{2+}$ Exchange Mechanism in the Smooth Muscle of Guinea-pig Stomach

Kim, Eui-Yong,Han, Jin,Kim, Ki-Whan The Korean Physiological Society 1992 대한생리학회지 Vol.26 No.1

The effects of changes in extracellular $Na^+\;and\;Ca^+$ concentration on the membrane potential and contractility were studied in the antral circular muscle of guinea pig stomach in order to elucidate the existence and the nature of $Na^+/Ca^{2+}$ exchange mechanism. All experiments were performed in tris buffered Tyrode solution which was aerated with 100% $O_2$ and kept at $35^{\circ}C.$ The treatment of $10^{-5}$ ouabain was performed to induce intracellular $Na^+$ loading prior to the start of experiment. The results were as follows: 1. $Na^+$-free Tyrode or high $Ca^{2+}$-Tyrode solution hyperpolarized the membrane potential and induced contracture. The time course of contracture was similar to that of change in membrane potential. 2. The degree of hyperpolarization and the amplitude of contracture decreased in accordance with the increase of extracellular $Na^+$ concentration. 3. $Na^+$-free contracture was developed even after blocking the influence of intrinsic nerves by the pretreatment with atropine, guanethidine and TTX. 4. $Ca^{2+}$-channel blockers(D-600 or $Mn^{2+}$) and the blocker of intracellular $Ca^{2+}$ release from sarcoplasmic reticulum(ryanodine) did not suppress the development of $Na^+$-free contracture. And also, dinitrophenol had no effect on $Na^+$-free contracture. 5. Dose-response relationship between extracellular $Na^+$ concentrations and the magnitude of contractures showed a sigmoid pattern. The slope of straight line from Hill plot was 2.7. 6. In parallel with the increase of extracellular $Ca^{2+}$ concentration, the amplitude of contracture increased dose dependently and was maximum at 8 mM $Ca^{2+}$-Tyrode solution. 7. The relationship between extracellular $Ca^{2+}$ concentrations and the magnitude of contractures showed hyperbolic pattern. The slope of straight line from Hill plot was 1.1. From the above results, it is suggested that $Na^+/Ca^{2+}$ exchange mechanism exists in the antral circular muscle of guinea pig stomach and this mechanism affects the membrane potential electrogenically.

A Study on the Na⁺/Ca²⁺ Exchange Mechanism in the Smooth Muscle of Guinea-pig Stomach

Kim. Eui-Yong,Han. Jin,Kim. Ki-Whan 대한생리학회 1992 대한생리학회지 Vol.26 No.1

The effects of changes in extracellular Na⁺ and Ca⁺ concentration on the membrane potential and contractility were studied in the antral circular muscle of guinea pig stomach in order to elucidate the existence and the nature of Na⁺/Ca²⁺ exchange mechanism. All experiments were performed in tris buffered Tyrode solution which was aerated with 100% O² and kept at 35℃. The treatment of 10^-5 ouabain was performed to induce intracellular Na⁺ loading prior to the start of experiment. The results were as follows: 1. Na⁺-free Tyrode or high Ca²⁺-Tyrode solution hyperpolarized the membrane potential and induced contracture. The time course of contracture was similar to that of change in membrane potential. 2. The degree of hyperpolarization and the amplitude of contracture decreased in accordance with the increase of extracellular Na⁺ concentration. 3. Na⁺-free contracture was developed even after blocking the influence of intrinsic nerves by the pretreatment with atropine, guanethidine and TTX. 4. Ca²⁺-channel blockers(D-600 or Mn²⁺) and the blocker of intracellular Ca²⁺ release from sarcoplasmic reticulum(ryanodine) did not suppress the development of Na⁺-free contracture. And also, dinitrophenol had no effect on Na⁺-free contracture. 5. Dose-response relationship between extracellular Na⁺ concentrations and the magnitude of contractures showed a sigmoid pattern. The slope of straight line from Hill plot was 2.7. 6. In parallel with the increase of extracellular Ca²⁺ concentration, the amplitude of contracture increased dose dependently and was maximum at 8 mM Ca²⁺-Tyrode solution. 7. The relationship between extracellular Ca²⁺ concentrations and the magnitude of contractures showed hyperbolic pattern. The slope of straight line from Hill plot was 1.1. From the above results, it is suggested that Na⁺/Ca²⁺ exchange mechanism exists in the antral circular muscle of guinea pig stomach and this mechanism affects the membrane potential electrogenically.

N,N-Dimethyl-D-erythro-Sphingosine Increases IntracellularCa2+ Concentration via Na+-Ca2+-Exchanger in HCT116Human Colon Cancer Cells

Hyo-Lim Kim,임동순 대한약학회 2008 Archives of Pharmacal Research Vol.31 No.1

N,N-dimethyl-D-erythro-sphingosine (DMS), an N-methyl derivative of sphingosine, is an inhibitor of protein kinase C (PKC) and sphingosine kinase (SK). In previous reports, DMS-induced intracellular Ca2+ increase concentration ([Ca2+]i) was studied in T lymphocytes, monocytes, astrocytes and neuronal cells. In the present study, we studied DMS-induced increase of [Ca2+]i in HCT116 human colon cancer cells. We found that the DMS-induced increase of [Ca2+]i in colon cancer cells is composed of Ca2+ release from intracellular Ca2+ stores and subsequent Ca2+ influx. The Ca2+ release is not related to modulation of inositol 1,4,5-trisphosphate (IP3) receptor or ryanodine receptor. On the other hand, the Ca2+ influx is mediated largely through Ca2+ channels sensitive to verapamil, nifedipine, Ga3+, and La3+. Furthermore, we found that the response is inhibited by bepridil and Ni2+, specific inhibitors of Na+-Ca2+-exchanger, suggesting involvement of Na+-Ca2+ exchanger in the DMS-induced [Ca2+]i increase in colon cancer cells. This inhibition was also observed in U937 monocytes, but not in 1321N1 astrocytes.

토끼 심방근 및 혈관 평활근에서의 $Na^{+}/Ca^{2+}$ 교환기전에 관한 연구

김희주,문형로,엄융의,호원경,Kim, Hee-Ju,Moon, Hyung-Ro,Earm, Yung-E,Ho, Won-Kyung 대한생리학회 1988 대한생리학회지 Vol.22 No.1

In order to elucidate the regulatory mechanism of intracellular calcium ion concentrations, contractions or contractures induced by $Na^{+}-removal$, calcium-application or ouabain-treatment as an index of $Na^+/Ca^{2+}$ exchange activity were studied in atrial muscle or vascular smooth muscle (aorta and renal artery) of the rabbit. The magnitude of low sodium contractures in atrial trabeculae increased with sigmoid shape when external sodium concentrations were reduced to sodium-free condition, whereas that of calcium contracture intensified in a parabolic pattern when external calcium concentrations were elevated to 8 mM. $Na^{+}-removal$ contractures were induced in a duration-dependent manner to $K^{+}-free$ exposure and same findings were observed with ouabain treatment. $Na^{+}-free$ contractures were not affected by verapamil treatment, but stimulated by $100{\mu}M\;Mn^{2+}$ and inhibited by high concentrations of $Mn^{2+}\;(2{\sim}8mM)$ in a dose-dependent manner. Ryanodine which is known to suppress the release of calcium from internal store abolished spontaneous twitch contractions induced by $K^{+}-free$ solution, but had no effect on the development $Na^{+}-free$ contractures. Na-free contractures were not always induced in vascular smooth muscle preparations. Contractures by $O\;mM\;Na^+$ were usually seen in aorta, but not often in renal artery.$50\;mM\;K^+$, noradrenaline (NA) and angiotensin II (AII) always evoked very large contraction in all preparations of vascular smooth muscle. Contractures developed by $O\;mM\;Na^+$ were not sensitive to verapamil treatment as in atrial trabeculae, but were abolished by $100{\mu}M\;Mn^{2+}$. In contrast to $Na^{+}-free$ contractures, $Mn^{2+}(100{\mu}M)$ had no effect on the contractures induced by NA or 50 mM$K^+$. Caffeine in the concentration of 10 mM evoked transient contracture in the distal renal artery. The rate of spontaneous relaxation in caffeine contracture was dependent upon the concentrations of external sodium, and had double component of relaxation when the rate of relaxation was plotted in the semilogarithmic scale of relative tension versus time. Especially late components of relaxation had more direct relation to $Na^+$ concentrations. It could be concluded that $Na^+/Ca^{2+}$ exchange mechanism in the heart has a large capacity, inhibited by $Mn^{2+}$ but not by verapamil and ryanodine, while $Na^+/Ca^{2+}$ exchange system in vascular smooth muscle has a very low capacity especially in small artery, inhibited by low concentration of $Mn^{2+}\;(100{\mu}M)$ but not affected by verapamil and ryanodine.

Na^(+)-Ca^(2+) exchange transport and pacemaker activity of the rabbit SA node

Park, So Ra,Suh, Chang Kook Yonsei University, College of Medicine 1991 Yonsei medical journal Vol.32 No.3

[ $Ca^{2+}$ ]-dependent Long-term Inactivation of Cardiac $Na^+/Ca^{2+}$ Exchanger

Lee, Jee-Eun,Kang, Tong-Mook The Korean Society of Pharmacology 2007 The Korean Journal of Physiology & Pharmacology Vol.11 No.5

Using BHK cells with stable expression of cardiac $Na^+/Ca^{2+}$ exchanger(BHK-NCX1), reverse mode(i.e. $Ca^{2+}$ influx mode) of NCX1 current was recorded by whole-cell patch clamp. Repeated stimulation of reverse NCX1 produced a cytosolic $Ca^{2+}$-dependent long-term inactivation of the exchanger activity. The degrees of inactivation correlated with NCX1 densities of the cells and were attenuated by reduced $Ca^{2+}$ influx via the reverse exchanger. The inactivation of NCX1 was attenuated by(i) inhibition of $Ca^{2+}$ influx with reduced extracellular $Ca^{2+}$, (ii) treatment with NCX1 blocker($Na^{2+}$), and (iii) increase of cytoplasmic $Ca^{2+}$ buffer(EGTA). In BHK-NCX1 cells transiently expressing TRPV1 channels, $Ca^{2+}$ influx elicited by capsaicin produced a marked inactivation of NCX1. We suggest that cytoplasmic $Ca^{2+}$ has a dual effect on NCX1 activities, and that allosteric $Ca^{2+}$ activation of NCX1 can be opposed by the $Ca^{2+}$-dependent long-term inactivation in intact cells.