• The Korean Journal of Physiology
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• 제24권2호
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• pp.281-291
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• 1990

The $Ca^{2+}-substitutional$ roles of strontium for the contractile processes were investigated in the rabbit renal artery. The contractions induced by either norepinephrine or high $K^+$ in the condition which intra- and extracellular $Ca^{2+}$ were replaced by $Sr^{2+}$, i.e. $Sr^{2+}-mediated$ contractions, were dose-dependent. And then the maximal amplitude of contraction, as compared with $Ca^{2+}-mediated$ contraction, was about 50% in norepinephrine and about 70% in high $K^+$. The $Sr^{2+}-mediated$ contractions were independent in the contraction by norepinephrine $(10^{-5}M)$ but dependent in those by high $K^+(100\;mM)$ on the extracellular $Sr^{2+}$ concentration. Also $Sr^{2+}-mediated$ contractions induced by norepinephrine were observed in the $Sr^{2+}-free$ Tyrode's solution. The $Sr^{2+}-mediated$ contractions induced by either norepinephrine or high $K^+$ were suppressed by verapamil, a $Ca^{2+}-channel$ blocker. By extracellular addition of $Sr^{2+}$, the $Ca^{2+}-mediated$ contractions induced by norepinephrine $(10^{-5}M)$ or 40 mM $K^+$ were inhibited but those by high $K^+(100\;mM)$ were increased. And the $Sr^{2+}-mediated$ contractions were increased by extracellular addition of $Ca^{2+}$ but did not reach the level of $Ca^{2+}-mediated$ contraction. Therfore it is suggested that in the vascular smooth muscle of rabbit renal artery $Sr^{2+}$ could enter the smooth muscle cells easily through the potential-operated calcium channel (POC) but not easily through the receptor-operated calcium channel (ROG), and $Sr^{2+}$ might be stored in the intracellular $Ca^{2+}-binding$ site and released by NE and induced the contraction by a way of activating directly the contractile apparatus.

• Journal of Plant Biology
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• 제37권3호
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• pp.271-276
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• 1994

The possibility that 1-aminocyclopropane-1-carboxylic acid (ACC)-uptake may be dependent on the H+-gradient established across the plsma membrane was tested in protoplasts isolated from 2.5 day old mungbean hypocotyls. The ACC-induced ethylene production was inhibited when the H+-gradient was collapsed by the treatment with carbonycyamide-p-trifluro-methoxy-phenylhydrazone (FCCP). Moreover, the treatment with o-vanadate, a specific inhibitor of plasma membrane H+-ATPase, caused the inhibition of ethylene production. The ACC-induced ethylene production was inhibited by the treatemnt with verapamil (Ca2+-channel blocker), or ethylene glycol-bis($\beta$-aminoethyl ether) N, N, N', N'-tetraacetic acid (EGTA) (Ca2+-chelator). In contrast, the ehtylene production was stimulated by the application of A23187 (Ca2+ ionophore). The inhibitory effect of EGTA in the ethylene producton was magnified in the presence of A23187. From these results, we suggest that the external Ca2+ influx to the cytosol resulted in the stimulatin of ACC oxidase activity after ACC-uptake resulting from a H+-gradient across the plasma membrane.

• 대한수의학회지
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• 제39권4호
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• pp.702-709
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• 1999

The present study was performed to elucidate the effects of extracellular $Ca^{2+}$ on contractile responses in isolated porcine coronary artery ring using by perivascular nerve stimulation (PNS). Especially, the study was focused on the source of $Ca^{2+}$ on $P_{2X}$-purinoceptor mediated muscle contraction which one of $P_2$-purinoceptor subtypes. The following results can be drawn from these studies : 1. The phasic contractions induced by PNS were inhibited with muscarinic receptor antagonist, atropine ($10^{-6}M$). 2. The phasic contractions induced by PNS were significantly inhibited by sequential treatment with atropine and adrenergic neural blocker, guanethidine ($10^{-6}M$). 3. The phasic contractions induced by PNS were inhibited with $P_{2X}$-purinoceptor desensitization by repetitive application of $\alpha$,$\beta$-Me ATP ($10^{-4}M$). 4. The phasic contractions induced by PNS were so weakened in calcium-free medium. 5. The phasic contractions induced by PNS were inhibited with calcium channel blocker, verapamil ($10^{-6}{\sim}5{\times}10^{-6}M$). 6. The phasic contractions induced by PNS on pretreated with verapamil ($10^{-6}{\sim}5{\times}10^{-6}M$) were not changed by $\alpha$,$\beta$-Me ATP ($10^{-4}M$). These results demonstrate that the neurogenic phasic contractions induced by PNS are due to adrenergic-, cholinergic- and $P_{2X}$-purinergic receptors and the origin of $Ca^{2+}$ on $P_{2X}$-purinoceptor mediated muscle contraction is extracellular $Ca^{2+}$ through plasmalemmal $Ca^{2+}$ channels.

• The Korean Journal of Physiology and Pharmacology
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• 제1권1호
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• pp.27-34
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• 1997

In the present study, it was aimed to further indentify the intracellular action mechansm of cromakalim and levcromakalim in the porcine coronary artery. In intact porcine coronary arterial strips loaded with fura-2/AM, acetylcholine caused an increase in intracellular free $Ca^{2+}$ $([Ca^{2+}]_i)$ in association with a contraction in a concentration-dependent manner. Cromakalim (1 ${\mu}M$) caused a reduction in acetylcholine-induced increased $[Ca^{2+}]_i$ not only in the mormal physiological salt solution (PSS) but also in $Ca^{2+}$-free PSS (containing 1 mM EGTA). In the skinned strips prepared by exposure of tissue to 20 .${\mu}M$ B-escin, inositol 1,4,5-trisphosphate ($IP_3$) evoked an increase in $[Ca^{2+}]_i$, but it was without effect on the intact strips. The $IP_3$-induced increase in $[Ca^{2+}]_i$ was inhibited by cromakalim by 78% and levcromakalim by 59% (1 .${\mu}M$, each). Pretreatment with glibenclamide (a blocker of ATP-sensitive $K^+$ channels, 10 .${\mu}M$) and apamin (a blocker of small conductance $Ca^{2+}$-activated $K^+$ channels, 1 .${\mu}M$) strongly blocked the effect of cromakalim and levcromakalim. However, charybdotoxin (a blocker of large conductance $Ca^{2+}$-activated $K^+$ channels, 1 .${\mu}M$) was without effect. In addition, cromakalim inhibited the $GTP{\gamma}S$ (100 .${\mu}M$, non-hydrolysable analogue of GTP)-induced increase in $[Ca^{2+}]_i$. Based on these results, it is suggested that cromakalim and levcromakalim exert a potent vasorelaxation, in part, by acting on the $K^+$ channels of the intracellular sites (e.g., sarcoplasmic reticulum membrane), thereby, resulting in decrease in release of $Ca^{2+}$ from the intracellular storage site.

• 대한수의학회지
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• 제34권3호
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• pp.493-500
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• 1994

The purpose of this study was to investigate the effects of neurotransmitters and the source of $Ca^{2+}$ in the effects of neurotransmitters on the motility of pig oviductal isthmic smooth muscle. The motility of the isolated smooth muscle was recorded by using physiological recording system. The results were summarized as follows; Acetylcholine, norepinephrine, histamine and prostaglandin $F_{2{\alpha}}(PGF_{2{\alpha}})$ caused the contraction and the contractile responses were increased in a dose-dependent manner from the concentration of $10^{-7}$ to $10^{-4}M$. The maximum contractility of acetylcholine, norepinephrine, histamine and $PGF_{2{\alpha}}$ was 65.99, 28.66, 83.99 and 47.33% of 100 mM K contraction, respectively. The contractile response induced by acetylcholine$(10^{-6}M)$ was completely blocked by the pretreatment with cholinergic receptor blocker, atropine$(10^{-6}M)$, the contractile response induced by norepinephrine$(10^{-5}M)$ was blocked by the pretreatment with ${\alpha}$-adrenergic receptor blocker, phentolamine$(10^{-6}M)$ but was not blocked and rather increased by the pretreatment with ${\beta}$-adrenergic receptor blocker. propranolol$(10^{-6}M)$, the contractile response induced by histamine$(10^{-6}M)$ was completely blocked by the pretreatment with $H_1$-histaminergic receptor blocker, pyrilamine$(10^{-6}M)$ but was increased by the pretreatment with $H_2$-histaminergic receptor blocker, cimetidine$(10^{-6}M)$. The contractile response induced by acetylcholine$(10^{-6}M)$, norepinephrine$(10^{-5}M)$ and histamine$(10^{-6}M)$ was weakly contracted response in $Ca^{2+}$-free medium, but the contractile response induced by $PGF_{2{\alpha}}(10^{-6}M)$ was disappeared. The contractile response induced by acetylcholine$(10^{-6}M)$, norepinephrine$(10^{-5}M)$ and histamine$(10^{-6}M)$ was powerfully depressed by the pretreatment with $Ca^{2+}$-channel blocker, verapamil$(10^{-5}M)$ but the contractile response induced by $PGF_{2{\alpha}}(10^{-6}M)$ was completely inhibited.

• The Korean Journal of Physiology and Pharmacology
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• 제15권5호
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• pp.279-283
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• 2011

Quercetin (3,3',4',5,7-pentahydroxyflavone) is an attractive therapeutic flavonoid for cancer treatment because of its beneficial properties including apoptotic, antioxidant, and antiproliferative effects on cancer cells. However, the exact mechanism of action of quercetin on ion channel modulation is poorly understood in bladder cancer 253J cells. In this study, we demonstrated that large conductance $Ca^{2+}$-activated $K^+$ ($BK_{Ca}$) or MaxiK channels were functionally expressed in 253J cells, and quercetin increased $BK_{Ca}$ current in a concentration dependent and reversible manner using a whole cell patch configuration. The half maximal activation concentration ($IC_{50}$) of quercetin was $45.5{\pm}7.2{\mu}m$. The quercetin-evoked $BK_{Ca}$ current was inhibited by tetraethylammonium (TEA; 5 mM) a non-specific $BK_{Ca}$ blocker and iberiotoxin (IBX; 100 nM) a $BK_{Ca}$-specific blocker. Quercetin-induced membrane hyperpolarization was measured by fluorescence-activated cell sorting (FACS) with voltage sensitive dye, bis (1,3-dibutylbarbituric acid) trimethine oxonol ($DiBAC_4$2(3); 100 nM). Quercetin-evoked hyperpolarization was prevented by TEA. Quercetin produced an antiproliferative effect ($30.3{\pm}13.5%$) which was recovered to $53.3{\pm}10.5%$ and $72.9{\pm}3.7%$ by TEA and IBX, respectively. Taken together our results indicate that activation of $BK_{Ca}$ channels may be considered an important target related to the action of quercetin on human bladder cancer cells.

• The Korean Journal of Physiology
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• 제24권2호
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• pp.353-362
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• 1990

Fluoride (F-), a known stimulator of G-protein, induced strong contraction in rabbit trachealis muscle. $AlCl_3\;(5{\sim}20\;{\mu}M)$, which is required for G-protein stimulation by $F^-$, potentiated the contractile response to $F^-$. $Ca^{2+}-removal$ and verapamil, a calcium channel blocker, inhibited the fluoroaluminate-induced contraction. Fluoroaluminate increased $^{45}Ca$ influx in the absence and presence of verapamil. In heparin-loaded muscle high $K^+-induced$ contraction was not affected, but acetylcholine and fluoroaluminate-induced contractions were inhibited. The fluoroaluminate-induced contraction was partially relaxed by isoproterenol, a stimulator of adenylate cyclase. Pertussis toxin partially inhibited fluoroaluminate-induced contraction and potentiated isoproterenol-induced relaxation in the presence of fluoroaluminate, but had no effect on acetylcholine-induced contraction and the isoproterenol-induced relaxation in the presence of acetylcholine. These results suggest that fluoroaluminate has the ability to stimulate at least two putative G-proteins in rabbit trachealis muscle; One causes $Ca^{2+}$ influx through the potential-operated $Ca^{2+}$ channel and the other induces intracellular $Ca^{2+}$ release by the increase of inositol-1, 4, 5-triphosphate.

• The Korean Journal of Physiology
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• 제27권2호
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• pp.115-122
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• 1993

There is evidence that noradrenaline enhances spontaneous contractions dose-dependently in guinea-pig antral circular muscle. To investigate the mechanism of this excitatory action, slow waves and membrane currents were recorded using conventional microelectrode techniques in muscle strips and the whole cell patch clamp technique in isolated gastric myocytes. On recording slow waves, noradrenaline $(10^{-5}\;M)$ induced the hyperpolarization of the membrane potential, although the shape of the slow waves became tall and steep. Also, spike potentiaIs occurred at the peaks of slow waves. These changes were completely reversed by administration of phentolamine $(10^{-5}\;M),\;an\;{\alpha}-adrenoceptor$ blocker. Noradrenaline-induced hyperpolarization was blocked by apamin $(10^{-7}\;M)$, a blocker of a class of $Ca^{2+}\;-dependent\;K^+$ channels. To investigate the mechanisms for these effects, we performed whole cell patch clamp experiments. Norndrenaline increased voltage-dependent $Ca^{2+}$ currents in the whole range of test potentials. Noradrenaline also increased $Ca^{2+}\;-dependent\;K^+$\;currents, and this effects was abolished by apamin. These results suggest that the increase in amplitude and the generation of spike potentials on slow waves was caused by the activation of voltage-dependent $Ca^{2+}$ channel via adrenoceptors, and hyperpolarization of the membrane potential was mediated by activation of apamin-sensitive $Ca^{2+}\;-dependent\;K^+\;channels$.

• Nutrition Research and Practice
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• 제12권3호
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• pp.183-190
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• 2018

BACKGROUND/OBJECTIVE: This study was designed to investigate how a Portulaca oleracea L. extract (POE) stimulates insulin secretion in INS-1 pancreatic ${\beta}-cells$. MATERIALS/METHOD: INS-1 pancreatic ${\beta}-cells$ were incubated in the presence of various glucose concentrations: 1.1 or 5.6, 16.7 mM glucose. The cells were treated with insulin secretagogues or insulin secretion inhibitor for insulin secretion assay using an insulin ELISA kit. In order to quantify intracellular influx of $Ca^{2+}$ caused by POE treatment, the effect of POE on intracellular $Ca^{2+}$ in INS-1 pancreatic ${\beta}-cells$ was examined using Fluo-2 AM dye. RESULTS: POE at 10 to $200{\mu}g/mL$ significantly increased insulin secretion dose-dependently as compared to the control. Experiments at three glucose concentrations (1.1, 5.6, and 16.7 mM) confirmed that POE significantly stimulated insulin secretion on its own as well as in a glucose-dependent manner. POE also exerted synergistic effects on insulin secretion with secretagogues, such as L-alanine, 3-isobutyl-1-methylxanthine, and especially tolbutamide, and at a depolarizing concentration of KCl. The insulin secretion caused by POE was significantly attenuated by treatment with diazoxide, an opener of the $K{^+}_{ATP}$ channel (blocking insulin secretion) and by verapamil (a $Ca^{2+}$ channel blocker). The insulinotropic effect of POE was not observed under $Ca^{2+}$-free conditions in INS-1 pancreatic ${\beta}-cells$. When the cells were preincubated with a $Ca^{2+}$ fluorescent dye, Fluo-2 (acetoxymethyl ester), the cells treated with POE showed changes in fluorescence in red, green, and blue tones, indicating a significant increase in intracellular $Ca^{2+}$, which closely correlated with increases in the levels of insulin secretion. CONCLUSIONS: These findings indicate that POE stimulates insulin secretion via a $K{^+}_{ATP}$ channel-dependent pathway in INS-1 pancreatic ${\beta}-cells$.

• Advances in Traditional Medicine
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• 제4권3호
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• pp.157-161
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• 2004

We showed the effects of the traditional herbal medicine, Jukyeoondam-tang (JO-T, Zhu-ru-Wen-Dan-Tang in Chinese), on ventricular arrhythmia induced by aconitine. Electrophysiological experiments with conventional microelectrode techniques revealed that JO-T potently suppressed the aconitine-induced arrhythmias in ventricular strips of the rat. In the aconitine-induced arrhythmia model of the rat, pretreatment with JO-T $(100\;{\mu}g/ml)$ completely occluded the appearance of ventricular tachyarrhythmia (VT) or ventricular fibrillation (VF) induced by aconitine. Furthermore, the aconitine-induced ventricular arrhythmia was occluded by $Na^+$ channel blocker quinidine but was not occluded by $K^+$ channel blocker glibenclamide $(3\;{\mu}mol/L)\;and\;Ca^{2+}$ channel blocker nifedipine $(10\;{\mu}mol/L)$. We also confirmed the effect of JO-T in the ischemia-reperfusion (I/R)-induced arrhythmia model of the rat. JO-T did not affect the I/R-induced arrhythmias in rats. JO-T may alleviate the risk of ventricular arrhythmias following aconitine. These results suggest that JO-T is a potent antiarrhythmic drug having a$Na^+$ channel-blocking action.