• The Korean Journal of Physiology and Pharmacology
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• v.20 no.3
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• pp.315-324
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• 2016

Human cardiac fibroblasts (HCFs) have various voltage-dependent $K^+$ channels (VDKCs) that can induce apoptosis. Hydrogen peroxide ($H_2O_2$) modulates VDKCs and induces oxidative stress, which is the main contributor to cardiac injury and cardiac remodeling. We investigated whether $H_2O_2$ could modulate VDKCs in HCFs and induce cell injury through this process. In whole-cell mode patch-clamp recordings, application of $H_2O_2$ stimulated $Ca^{2+}-activated$ $K^+$ ($K_{Ca}$) currents but not delayed rectifier $K^+$ or transient outward $K^+$ currents, all of which are VDKCs. $H_2O_2-stimulated$ $K_{Ca}$ currents were blocked by iberiotoxin (IbTX, a large conductance $K_{Ca}$ blocker). The $H_2O_2-stimulating$ effect on large-conductance $K_{Ca}$ ($BK_{Ca}$) currents was also blocked by KT5823 (a protein kinase G inhibitor) and 1 H-[1, 2, 4] oxadiazolo-[4, 3-a] quinoxalin-1-one (ODQ, a soluble guanylate cyclase inhibitor). In addition, 8-bromo-cyclic guanosine 3', 5'-monophosphate (8-Br-cGMP) stimulated $BK_{Ca}$ currents. In contrast, KT5720 and H-89 (protein kinase A inhibitors) did not block the $H_2O_2-stimulating$ effect on $BK_{Ca}$ currents. Using RT-PCR and western blot analysis, three subtypes of $K_{Ca}$ channels were detected in HCFs: $BK_{Ca}$ channels, small-conductance $K_{Ca}$ ($SK_{Ca}$) channels, and intermediate-conductance $K_{Ca}$ ($IK_{Ca}$) channels. In the annexin V/propidium iodide assay, apoptotic changes in HCFs increased in response to $H_2O_2$, but IbTX decreased $H_2O_2$-induced apoptosis. These data suggest that among the VDKCs of HCFs, $H_2O_2$ only enhances $BK_{Ca}$ currents through the protein kinase G pathway but not the protein kinase A pathway, and is involved in cell injury through $BK_{Ca}$ channels.

• The Korean Journal of Physiology and Pharmacology
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• v.6 no.2
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• pp.93-99
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• 2002

Effects of oxidized low-density lipoprotein (ox-LDL), $1-{\alpha}-stearoyl-lysophosphatidylcholine$ (LPC), on intracellular $Ca^{2+}$ concentration were examined in mouse endothelial cells by measuring intracellular $Ca^{2+}$ concentration $([Ca^{2+}]_i)$ with fura 2-AM and reverse transcription-polymerase chain reaction (RT-PCR). LPC increased $[Ca^{2+}]_i$ under the condition of 1.5 mM $[Ca^{2+}]_o$ but did not show any effect under the nominally $Ca^{2+}-free$ condition. Even after the store depletion with $30{\mu}M$ 2,5-di-tert- butylhydroquinone (BHQ) or $30{\mu}M$ ATP, LPC could still increase the $[Ca^{2+}]_i$ under the condition of 1.5 mM $[Ca^{2+}]_o.$ The time required to increase [$Ca{2+}$]i (about 1 minute) was longer than that for ATP-induced $[Ca^{2+}]_i$ increase $(10{\sim}30\;seconds).$ LPC-induced $[Ca^{2+}]_i$ increase was completely blocked by $1{\mu}M\;La^{3+}.$ Transient receptor potential channel(trpc) 4 mRNA was detected with RT-PCR. From these results, we suggest that LPC increased $[Ca^{2+}]_i$ via the increase of $Ca^{2+}$ influx through the $Ca^{2+}$ routes which exist in the plasma membrane.

• The Korean Journal of Physiology
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• v.20 no.1
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• pp.31-41
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• 1986

The sufficient myoplasmic $Ca^{++}$ to react with the contractile proteins is necessary to induce contraction of a cardiac muscle. These $Ca^{++}$ for the production of muscle contraction are supplied from the three recognized $Ca^{++}$ sources; internal $Ca^{++}$ release via the sarcoplasmic reticulum(SR), $Ca^{++}$ influx through a gated Ca-channel in the membrane as a Isi, and $Ca^{++}$ transport by the mechanism of Na/ca exchange. However, it is still controversial which $Ca^{++}$ sources act as a main contributor for myoplasmic $Ca^{++}$, Therefore, this study was undertaken in order to examine the $Ca^{++}$ sources for the contraction of frog ventricle. There is evidence that the SR is sparse in frog ventricular fibers, and that T-tubules are absent. Isolated ventricular strips of frog, Rana nigromaculata, were used in this experiment. Isometric tension was recorded by force transducer, and membrane potentials of ventricular muscles were measured through the intracellular glass microelectrodes, which were filled with 3M KCI and had resistance of $30{\pm}50M{\Omega}$. All experiments were performed at room temperature in a tris·buffered Ringer solution which was aerated with 100% $O_2$. Isotonic high K, low Na solution was used to induce K-contracture, K-contracture appeared at the concentration of 20 to 30mM-KCI and was potentiated in parallel with the increase in KCI concentration. The contracture had two components: an initial rapid phasic and a subsequent slow tonic contractile responses. Membrane Potentials measured at normal Ringer solution(2.5mM KCI) was -90 to -100 mV, and decreased linearly as the KCI concentration increased; -55mV at 20mM.KCI, -45mV at 30 mM.KCI, -30 mY at 50 mM.KCI, and -12 mV at 100 mM.KCI. K-contracture was evoked firstly at the membrane potential of -45 mV. The contracture was potentiated by the increase of bathing extracellular $Ca^{++}$ concentration. However, in the absence of $Ca^{++}$ the contracture was almost not induced by 50 mM.KCI solution. Caffeine(20mM) in normal Ringer solution, which is known to release $Ca^{++}$ from SR without substantial effects on the $Ca^{++}$ fluxes across the surface membrane, did not affect membrane potential and also not initiate contracture, but the caffeine in 20 mM-KCI Ringer solution produced a contracture. Above results suggest that the main $Ca^{++}$ source for the K·contracture of frog ventricle is $Ca^{++}$ influx through the voltage-dependent Ca-channel, and that in the K-contracture at the concentration of 100 mM-KCI, the mechanism of Na/ca exchange also partly contributs, in addition to the $Ca^{++}$ influx.

• Journal of Korean Physical Therapy Science
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• v.11 no.1
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• pp.20-27
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• 2004

It is widely accepted that smooth muscle contraction is triggered by intracellular $Ca^{2+}$ ($[Ca^{2+}]_i$) released from intracellular $Ca^{2+}$ stores such as sarcoplasmic reticulum (SR) and from the extracellular space, The increased $[Ca^{2+}]_i$ can phosphorylate the 20-kDa myosin light chain ($MLC_{20}$) by activating MLC kinase (MLCK), and this initiates smooth muscle contraction. In addition to the $[Ca^{2+}]_i$-MLCK-tension pathway, a number of intracellular signal molecules, including mitogen-activated protein kinase (MAPK), protein kinase C (PKC), phosphatidylinositol 3-kinase (PI3K), and Rho-associated coiled coil-forming protein kinase (ROCK), play important roles in the regulation of smooth muscle contraction. However, the mechanisms regulating contraction of caldesmon (CaD), actin-binding protein, are not entirely elucidated in the presence of $Ca^{2+}$. It is known that CaD tightly interacts with actin and inhibits actomyosin ATPase activity. Therefore, the purpose of the present study was to investigate the roles of $Ca^{2+}$-dependent CaD in smooth muscle contraction. Endothelin-1 (ET-1), G-protein coupled receptor agonist and vasoconstrictor, increased both vascular smooth contraction and phosphorylation of CaD in the presence of $Ca^{2+}$. These results suggest that ET-1 induces contraction and phosphorylation of CaD in rat aortic smooth muscle, which may he mediated by the increase of $[Ca^{2+}]_i$.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.2
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• pp.153-159
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• 1987

Adsorption and desorption characteristics of $^{42}K$ and $^{45}Ca$ were studied by making use of the natural zeolite, bentonite, and vermiculite. The work included that the fittness tests for the Freundlich and the Langmuir adsorption isotherms and desorption of the radionuclides from adsorbents by extracting with $NH^+_4$ ($1N-NH_4OAc$). The adsorption by the radionuclides are fitted well with both of the adsorption equations. The Langmuir adsorption maximum of $^{42}K$ is higher than that of $^{45}Ca$ by the zeolite and bentonite except vermiculite, and the values of $^{42}K$ decrease in the order of Zeolite (Zt)>Bentonite (Bt)>Vemiculite (Vt). As for $^{45}Ca$, the maximum adsorption values decrease in the order of Bt>Vt>Zt. The ionic radii of K and Ca seem to be closely related with fixation in the cavity of the zeolite that adsorb more $^{42}K$ than $^{45}Ca$. The smaller ionic size of Ca seems to be resulted in the lower adsorption of $^{45}Ca$ by the zeolite because Ca could leave easily from the cavity. Ionic size of K, however, seems to be similar with size of the cavity. $^{45}Ca$ adsorption by the bentonite, on the other hand, show higher adsorption than $^{42}K$. The higher charge density of the divalent cations than those of the monovalent cations seems to be the main consideration. For the retention strength of the adsorbed $^{42}K$ and $^{45}Ca$ by the adsorbents, a comparison is made by use of the Langmuir constant(k). The results indicated that the constant values for K are smaller than those of Ca in all the adsorbents. It seems that the smaller values of the constant, the weaker retention strength. For $^{42}K$, the percentage of desorption decrease in the order of Zt>Bt>Vt, but in the case of $^{45}Ca$, it decreases in the order of Vt>Zt>Bt. The results show that the weaker binding strength as represented by small value of the Langmuir constant, the higher percentage of the removal except fixing preferably $K^+$ by the vemiculite. In conclusion, the zeolite could adsorb much more $^{42}K$ and remove it more than others. For $^{45}Ca$, the bentonite could adsorb more and desorb less than others.

• Journal of Life Science
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• v.27 no.10
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• pp.1111-1120
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• 2017

This study was conducted to select pepper lines that were tolerant to excessive water injury among the pepper germplasm and investigate the genetic characteristics of those lines to contribute to the breeding of pepper cultivars with stable productivity in abnormal weather. Each of the tolerant and susceptible lines went through immersion treatment, and differentially expressed genes between them were analyzed. The tolerant line showed increased expression of the CA02g26670 gene, which is involved in the CONSTANS protein pathway and regulation of flowering by day length, but it exhibited decreased expressions of CA01g21450, CA01g22480, CA01g34470, CA02g00370 and CA02g00380. The susceptible line showed increased gene expressions of CA02g09720, CA02g21290, CA03g16520, CA07g 02110, and CA12g17910, which are involved in the inhibition of proteolytic enzyme activity, DNA binding, inhibition of cell wall-degrading enzyme, and inhibition of nodulin, respectively. Meanwhile the expressions of CA02g02820, CA03g21390, CA06g17700 and CA07g18230 decreased in the susceptible line, in relation to calcium-ion binding, high temperature, synthesis of phosphocholine and cold stress, respectively. The expressions of genes related to apoptosis and peroxidase increased, while that of CA02g16990, which functions as a nucleoside transporter, decreased in both the tolerant and susceptible lines. Based on the different gene expressions between the tolerant and susceptible lines, further studies are needed on breeding abiotic stress-tolerant lines.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.2
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• pp.51-58
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• 2008

Cardiac fibroblasts constitute one of the largest cell populations in the heart, and contribute to structural, biochemical, mechanical and electrical properties of the myocardium. Nonetheless, their cardiac functions, especially electrophysiological properties, have often been disregarded in studies. $Ca^{2+}$-activated $K^+\;(K_{Ca})$ channels can control $Ca^{2+}$ influx as well as a number of $Ca^{2+}$-dependent physiological processes. We, therefore, attempted to identify and characterize $K_{Ca}$ channels in rat Cardiac fibroblasts. First, we showed that the cells cultured from the rat ventricle were cardiac fibroblasts by immunostaining for discoidin domain receptor 2 (DDR-2), a specific fibroblast marker. Secondly, we detected the expression of various $K_{Ca}$ channels by reverse transcription polymerase chain reaction (RT-PCR), and found all three family members of $K_{Ca}$ channels, including large conductance $K_{Ca}$ (BK-${\alpha}1-\;and\;-{\beta}1{\sim}4$subunits), intermediate conductance $K_{Ca}$ (IK), and small conductance $K_{Ca}$ (SK$1{\sim}4$ subunits) channels. Thirdly, we recorded BK, IK, and SK channels by whole cell mode patch clamp technique using their specific blockers. Finally, we performed cell proliferation assay to evaluate the effects of the channels on cell proliferation, and found that the inhibition of IK channel increased the cell proliferation. These results showed the existence of BK, IK, and SK channels in rat ventricular fibroblasts and involvement of IK channel in cell proliferation.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.1
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• pp.31-35
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• 2008

Lysophosphatidylcholine (LPC), a metabolite of membrane phospholipids by phospholipase $A_2$, has been considered responsible for the development of abnormal vascular reactivity during atherosclerosis. $Ca^{2+}$ influx was shown to be augmented in atherosclerotic artery which might be responsible for abnormal vascular reactivity. However, the mechanism underlying $Ca^{2+}$ influx change in atherosclerotic artery remains undetermined. The purpose of the present study was to examine the effects of LPC on L-type $Ca^{2+}$ current $(I_{Ca(L)})$ activity and to elucidate the mechanism of LPC-induced change of $I_{Ca(L)}$ in rabbit portal vein smooth muscle cells using whole cell patch clamp. Extracellular application of LPC increased $I_{Ca(L)}$ through whole test potentials, and this effect was readily reversed by washout. Steady state voltage dependency of activation or inactivation properties of $I_{Ca(L)}$ was not significantly changed by LPC. Staurosporine (100 nM) or chelerythrine $(3{\mu}M)$, which is a potent inhibitor of PKC, significantly decreased basal $I_{Ca(L)}$, and LPC-induced increase of $I_{Ca(L)}$ was significantly suppressed in the presence of PKC inhibitors. On the other hand, application of PMA, an activator of PKC, increased basal $I_{Ca(L)}$ significantly, and LPC-induced enhancement of $I_{Ca(L)}$ was abolished by pretreatment of the cells with PMA. These findings suggest that LPC increased $I_{Ca(L)}$ in vascular smooth muscle cells by a pathway that involves PKC, and that LPC-induced increase of $I_{Ca(L)}$ might be, at least in part, responsible for increased $Ca^{2+}$ influx in atherosclerotic artery.

• Korean Journal of Food Science and Technology
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• v.29 no.5
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• pp.1071-1074
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• 1997

The Effect of $Ca^{++}$, $K^+$ and $Mg^{++}$ on salting of radish was investigated. Up to 0.2 M of $Ca^{++}$ and/or $K^+$, sodium chloride content of radish increased respectively, comparing with no addition of these ions. The salting effect of radish incereased in proportion to the concentration ($0{\sim}0.01\;M$) of $Ca^{++}$ and/or $K^+$ in the salting solution up to 0.2 M, while there was no influence of $Mg^{++}$. When $Mg^{++}$ and $Ca^{++}/Mg^{++}$ and $K^+$ were added to brine solution, $Ca^{++}$ or $K^+$ influenced the salting effect of radish and $Mg^{++}$ did not.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.329-335
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• 1995

Rheological properties of whole soybean gel(soygel) were investigated as affected by the water addition ratio, stirring time and Ca salts. The soygel was prepared by suspension of whole soy flour(WSF, 300 mesh) in boiling water, addition of sodium alginate and Ca salts followed by thorough mixing and gel formation at $4^{\circ}C$. The texture properties of hardness, adhesiveness and cohesiveness of the gel were increased as the stirring time prolonged from 5 to 30 minutes. From the results of the rheological and sensory properties, 20 minutes of stirring time was selected for whole soybean gel preparation. Eventhough increase in water addition ratio from 8 to 12 times(water/WSF, v/w) resulted a decrease in hardness and adhesiveness, 10 times ratio was chosen as proper the water addition based on textural uniformity. Among the Ca salts, $CaSO_4$ produced the highest hardness followed by Ca $gluconate-CaSO_4$ mixture(413g) and Ca gluconate at the water addition level of 10 times. In order to determine the amounts of Ca salts, and 0.125g of Ca gluconate or $CaSO_4$ per g WSF were found to be optimum in terms of textural and sensory properties. The proper mixing ratio of Ca gluconate and $CaSO_4$ was found to be 50 : 50, 25 : 75 and 0 : 100.