• Biomolecules & Therapeutics
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• 제16권3호
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• pp.219-225
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• 2008

Taurine is the most abundant amino acid in many tissues and is found to be enhancing the bone tissue formation or inhibits the bone loss. Although it is reported that taurine reduces the alveolar bone loss through inhibiting the bone resorption, its functions of taurine and expression of taurine transporter (TauT) in bone have not been identified yet. The purpose of this study is to clarify the uptake mechanism of taurine in osteoblast using mouse osteoblast cell lines. In this study, mouse stromal ST2 cells and mouse osteoblast-like MC3T3-E1 cells as osteoblast cell lines were used. The activity of taurine uptake was assessed by measuring the uptake of [$^3H$]taurine in the presence or absence of inhibitors. TauT mRNA was detected in ST2 and MC3T3-E1 cells. [$^3H$]Taurine uptake by these cells was dependent on the presence of extracellular calcium ion. The [$^3H$]taurine uptake in ST2 cells treated with 4 mM calcium was increased by 1.7-fold of the control which was a significant change. In contrast, in $Ca^{++}$-free condition and L-type calcium channel blockers (CCBs), taurine transport to osteocyte was significantly inhibited. In oxidative stress conditions, [$^3H$]taurine uptake was decreased by TNF-$\alpha$ and $H_2O_2$. Under the hyperosmotic conditions, taurine uptake was increased, but inhibited by CCBs in hyperosmotic condition. These results suggest that, in mouse osteoblast cell lines, taurine uptake by TauT was increased by the presence of extracellular calcium, whereas decreased by CCBs and oxidative stresses, such as TNF-$\alpha$ and $H_2O_2$.

• 대한약리학회지
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• 제17권2호
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• pp.7-16
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• 1981

심근 수축기전에 있어서 중심적인 역할을 하는 칼슘 이온과 Hienamine과의 상호작용을 비교 검토하였고 아울러 이 강심효과에 대하여 칼슘길항제인 란타눔과 verapamil을 사용하여 이에 미치는 영향을 관찰하였다. Higenamine은 적출 가토좌심방근에 대해 심근의 칼슘과 상호보완적인 상승 및 상가작용을 나타내었고 Higenamine $10^{-7}g/ml$은 0.058mM의 칼슘과 동등한 심근 수축증강효과를 나타내었으며 부자부타놀 분획물과 비교할 때 약 1,000배 정도 강력한 강심작용을 나타내었다. 또한 심근세포막의 칼슘유입을 억제한 조건인 란타눔과 verapamil처치시에도 Higenamine은 용량의존적으로 저하된 심근 수축력을 회복시킴으로 미루어 볼 때 Higenamine외 강심작용기전의 일부는 세포막을 통한 칼슘의 유입을 촉진시키는 것일 것으로 추측하였다.

• Journal of Ginseng Research
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• 제22권2호
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• pp.126-132
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• 1998

In the present study, we examined effects of ginseng saponins (ginsenosides) on pp60c-src protein tyrosine kinase (PTK) activity, intracellular calcium concentration ([$Ca^{2+}$]i), and cell proliferation in NIH3T3 cells. Eight different ginsenosides [ginsenoside-Rb1 (G-$Rb_1$), -$Rb_2$, -Rc, -Rd, -Re, -Rf, -$Rg_1$, -$Rg_2$) and ginseng total saponin (GTS) were used for these experiments. All ginsenosides and GTS tested stimulated the activation of $pp60^{c-src}$ kinase, and especially G-$Rb_1$,-Rd,-$Rg_1$, and -$Rg_1$ showed a higher stimulatory effect than others at 16.7 $\mu\textrm{g}$/ml of ginsenosides with a 18 hr-incubation, increasing the activity by 4.5, 3.5, 3.5, and 3.0-fold, respectively, over that of untreated control. In addition, both G-Rd and -$Rg_2$)Rg2 increased ($Ca^{2+}$), to 202 and 334 nM, respectively, about 2-3-fold above the basal level within 7min at 250 $\mu\textrm{g}$/yml of ginsenosides. The increases of ($Ca^{2+}$), were eliminated by Pretreatment of EGTA, an extracellular calcium chelator, suggtasting that they result from an influx of calcium ion from extracellular medium rather than an efflux from intracellular calcium store, endoplasmic reticulum (ER). All ginsenosides studied enhanced cell proliferation to 1.2-1.4-fold over that of untreated control at 5~250 $\mu\textrm{g}$/ml of concentrations. Interestingly the promotion of cell proliferation by ginsenosides corresponded with the activation of c-src kinase, which is an early step in the mitogenic signaling cascade. Taken together, we suggest that some ginsenosides may lead to cellProliferation via the activation of cellular signal transduction Pathway involving $pp60^{c-src}$ kinase.

• 대한수의학회지
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• 제34권1호
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• pp.25-36
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• 1994

The inward tail current after a short depolarizing pulse has been known as Na-Ca exchange current activated by intracellular calcium which forms late plateau of the action potential in rabbit atrial myocytes. Chloride conductance which is also dependent upon calcium concentration has been reported as a possible tail current in many other excitable tissues. Thus, in order to investigate the exsitance of the calcium activated chloride current and its contribution to tail current, whole cell voltage clamp measurement has been made in single atrial cells of the rabbit. The current was recorded during repolarization following a brief 2 ms depolarizing pulse to +40mV from a holding potential of -70mV. When voltage-sensitive transient outward current was blocked by 2 mM 4-aminopyridine or replacement potassium with cesium, the tail current were abolished by ryanodine$(1{\mu}M)$ or diltiazem$(10{\mu}M)$ and turned out to be calcium dependent. The magnitudes of the tail currents were increased when intracellular chloride concentration was increased to 131 mM from 21 mM. The current was decreased by extracellular sodium reduction when intracellular chloride concentration was low(21 mM), but it was little affected by extracellular sodium reduction when intracellual chloride concentration was high(131 mM). The current-voltage relationship of the difference current before and after extracellular sodium reduction, shows an exponential voltage dependence with the largest magnitude of the current occurring at negative potentials, with is similar to current-voltage relationship at negative potentials, which is similar to current-voltage relationship of Na-Ca exchange current. The current was also decreased by $10{\mu}M$ niflumic acid and 1 mM bumetanide, which is well known anion channel blockers. The reversal potentials shifted according to changes in chloride concentration. The current-voltage relationships of the niflumic acid-sensitive currents in high and low concentration of chloride were well fitted to those predicted as chloride current. From the above results, it is concluded that calcium activated chloride component exists in the tail current with Na-Ca exchange current and it shows the reversal of tail current. Therefore it is thought that in the physiologic condition it leads to rapid end of action potential which inhibits calcium influx and it contributes to maintain the low intracellular calcium concentration with Na-Ca exchange mechanism.

• 한국환경성돌연변이발암원학회지
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• 제22권4호
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• pp.229-235
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• 2002

Thimerosal, a widely used preservative, has been well known to induce intracellular calcium mobilization in various cell types. However, the mechanism of its calcium mobilization is not clearly understood yet. For studying the mechanism of thimerosal-mediated calcium release, we have used HL60 cells in calcium-free Lockes solution that has no extracellular calcium. Thimerosal significantly reduced the lag period of initial calcium release whereas it enhanced the rate and magnitude of the calcium release in a dose-dependent manner. At the same time, we found that thimerosal generated superoxide anion by activating NADPH oxidase in dose- and time-dependent manner. Interestingly, the kinetics and the dosedependency of superoxide anion generation were very similar to those of intracellular calcium mobilization. In inhibitors study, the thimerosal-induced superoxide anion generation was significantly suppressed by DMSO as well as superoxide dismutase but not by genistein or EGTA. Surprisingly, the pretreatment with N-Acetyl-$_{L}$-Cysteine blocked almost completely the thimerosal-induced calcium increase, indicating that ROS playa key role in the calcium mobilization. The present results suggest that thimerosal-induced calcium mobilization is possibly mediated by the activation of NADPH oxidase and subsequent ROS generation.n.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1994년도 춘계학술대회 and 제3회 신약개발 연구발표회
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• pp.217-217
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• 1994

Calcium entry blockers, capable of inhibiting transmembrane influx of extracellular calcium through specific calcium channels, are useful drugs in the treatment of angina pectoris, hypertension, cardiac arrythmia, and various cardiovascular disorders. Compounds having isoquinoline structures have recently been reported to possess calcium antagonistic action. Therefore, in the present study, we have attempted to synthesize some isoquinoline and related compound.; in order to search for potentially effective chemicals acting on cardiovascular system, and evaluated their pharmacological properties focusing on calcium antagonistic actions. Almost all of the compounds so far synthesized, had inhibitory action against phenylephrine or high potassium-induced contraction in vascular smooth muscle with different degrees of potencies depending on their structures, However, some of tetrahydroisoquinoline analogs showed directly inhibit calcium current in isolated rabbit cardiac myocytes examined by patch clamp techniques. The pharmacological properties of these compounds need more intensive investigation as to whether these chemicals may have developed as a new cardiovascular active drugs. Therefore, we are now under investigation of the mechanism of action of these compounds.

• Bulletin of the Korean Chemical Society
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• 제23권10호
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• pp.1451-1489
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• 2002

Sphingosine is known to regulate a wide range of cell physiology including growth, differentiation, and apoptosis. In this study, we examined the effect of sphingosine on the phospholipase D (PLD) activity in rat thymocytes. Sphingosine potently stimulated PLD in the absence of extracellular calcium, while depletion of intracellular calcium by BAPTA/AM treatment completely blocked activation of PLD by sphingosine. Sphingosine-induced increase of the intracellular calcium concentration was confirmed using a fluorescent calcium indicator Fluo-3/AM. A phosphoinositide-specific phospholipase C inhibitor U73122 partially inhibited the stimulation of PLD by sphingosine. When mouse PLD2 gene was transfected into mouse thymoma EL4 cells, which lack intrinsic PLD activity, sphingosine could stimulate PLD2 significantly while overexpression of human PLD1 had no effect. Taken together, the sphingosine-stimulated PLD activity in rat thymocytes is dependent on the mobilization of intracellular calcium and appears to be due to the PLD2 isoform.

• Toxicological Research
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• 제22권4호
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• pp.397-402
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• 2006

Lipid mediator such as lysophosphatidic acid (LPA) plays an important role in inflammation and wound heating, has been recently reported to induce influx of extracellular calcium into erythrocytes. This elevation in intracellular calcium level may cause destruction of membrane asymmetry and procoagulant microvesicle formation. Thus, we investigated if the lipid mediator could induce microvesicle formation as a result of extracellular calcium influx in human erythrocytes. Treatment with lipid mediator to erythrocytes resulted in microvesicle generation In a concentration-, time-dependent manner. Microvesicles formed expressed procoagulant phosphatidylserine (PS) on their surface membrane significantly as well. LPA did not affect the band 3 phosphorylation which is involved in morphological change in erythrocytes. Pretreatment with suramin did not inhibit LPA-induced microvesicle generation, suggesting microvesicle generation was not receptor-dependent pathway. Depletion of intracellular ATP levels in erythrocytes was suggested to be one of the mechanism for these events.

• 대한약학회:학술대회논문집
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• 대한약학회 2000년도 춘계총회 및 학술대회
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• pp.122.2-123
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• 2000

• Journal of Plant Biology
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• 제38권3호
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• pp.243-250
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• 1995

Involvement of calcium in signal transduction of salt stress was investigated in 1.7 M NaCl adapted Dunaliella salina, extremely halotolerant, unicellular green alga. When hyperosmotic (3.4 M NaCl) or Hypoosmotic (0.8 M NaCl) stress was treated, extracellular calcium was influxed in or intracellular calcium effluxed from D. salina, respectively, and these fluxes were proportional to the degree of stress. This might indicate indirectly that the change of calcium level occurred within the cells. In addition, the change of calcium flux was ahead of glycerol synthesis which has been known as the physiological response to salt stress. Osmoregulation was affected byextracellular calcium concentration, and increase of glycerol content as an osmoticum was inhibited about 50% by treatment of TFP and W-7 known as calmodulin specific inhibitors. Furthermore, in the case of the hyperosmotic stressed cells, the amount of 21 kD and 39 kD protein appeared to be calcium binding protein were increased. Among these, the 39 kD protein was detected only in the hyperosmotic stressed cells. The results obtained in the present work suggest that the possibility of calcium as a second messenger in the transduction of salt stress signal exists in the osmoregulation system of D. salina.