• The Korean Journal of Physiology and Pharmacology
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• 제13권3호
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• pp.241-249
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• 2009

Although extracellular $Ca^{2+}$ entry through the voltage-dependent $Ca^{2+}$ channels plays an important role in the spontaneous phasic contractions of the pregnant rat myometrium, the role of the T-type $Ca^{2+}$ channels has yet to be fully identified. The aim of this study was to investigate the role of the T-type $Ca^{2+}$ channel in the spontaneous phasic contractions of the rat myometrium. Spontaneous phasic contractions and $[Ca^{2+}]_i$ were measured simultaneously in the longitudinal strips of female Sprague-Dawley rats late in their pregnancy (on day 18 ${\sim}$ 20 of gestation: term=22 days). The expression of T-type $Ca^{2+}$ channel mRNAs or protein levels was measured. Cumulative addition of low concentrations (< 1 ${\mu}M$) of nifedipine, a L-type $Ca^{2+}$ channel blocker, produced a decrease in the amplitude of the spontaneous $Ca^{2+}$ transients and contractions with no significant change in frequency. The mRNAs and proteins encoding two subunits (${\alpha}$ 1G, ${\alpha}$ 1H) of the T-type $Ca^{2+}$ channels were expressed in longitudinal muscle layer of rat myometrium. Cumulative addition of mibefradil, NNC 55-0396 or nickel induced a concentration-dependent inhibition of the amplitude and frequency of the spontaneous $Ca^{2+}$ transients and contractions. Mibefradil, NNC 55-0396 or nickel also attenuated the slope of rising phase of spontaneous $Ca^{2+}$ transients consistent with the reduction of the frequency. It is concluded that T-type $Ca^{2+}$ channels are expressed in the pregnant rat myometrium and may play a key role for the regulation of the frequency of spontaneous phasic contractions.

• The Korean Journal of Physiology and Pharmacology
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• 제5권5호
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• pp.413-421
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• 2001

An impaired smooth muscle cell (SMC) relaxation of coronary artery by alteration of $K^+$ channels would be the most potential explanation for reduced coronary reserve in left ventricular hypertrophy (LVH), however, this possibility has not been investigated. We performed morphometrical analysis of the coronary artery under electron microscopy and measured $Ca^{2+}-activated\;K\;(K_{Ca})$ currents and delayed rectifier K $(K_{dr})$ currents by whole-cell and inside-out patch-clamp technique in single coronary arterial SMCs from rabbits subjected to isoprenaline-induced cardiac hypertrophy. Coronary arterial SMCs underwent significant changes in ultrastructure. The unitary current amplitude and the open-state probability of $K_{Ca}$ channel were significantly reduced in hypertrophy without open-time and closed-time kinetic. The concentration-response curve of $K_{Ca}$ channel to $Ca^{2+}$ is shifted to the right in hypertrophy. The reduction in the mean single channel current and increase in the open channel noise of $K_{Ca}$ channel by TEA were more sensitive in hypertrophy. $K_{dr}$ current density is significantly reduced in hypertrophy without activation and inactivation kinetics. The sensitivity of $K_{dr}$ current on 4-AP is significantly increased in hypertrophy. This is the first study to report evidence for alterations of $K_{Ca}$ channels and $K_{dr}$ channels in coronary SMCs with LVH. The findings may provide some insight into mechanism of the reduced coronary reserve in LVH.

• Journal of Plant Biology
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• 제34권3호
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• pp.239-244
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• 1991

Ca2+ is implicated as a second messenger in coupling various stimuli such as hormone, gravity and light. The determine whether or not plant hormones mobilize calcium with different action, we investigated the cytosolic Ca2+ changes by IAA and zeatin in the protoplasts isolated from elongating mesocotyl of maize. IAA increased the influx of Ca2+ due to the calcium channel opening, which was confirmed by using verapamil, calcium channel blocker. On the other hand, zeatin increased the cytosolic Ca2+ by promoting the efflux of Ca2+ derived from cellular organelles. These results suggest that different calcium flux induced by IAA and zeatin plays a role in appropriate response resulting in increase of cell elongation or repression cell elongatoin.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 1999년도 학술발표회 진행표 및 논문초록
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• pp.61-62
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• 1999

;The mechanisms inducing hypertension are actively investigated and are still challenging topics. Basically hypertension must be caused by the disorder of $Ca^{2+}$ metabolism in vascular smooth muscle, such as the increase of $Ca^{2+}$ influx, the decrease of ci+ efflux, or the change of sensitivity of contractile protein etc. The one of cause of the increase of ci+ influx may be the change of ci+ channel activity. Even though the relationships of ci+ channel activity and hypertension were studied using various hypertension models, still it is not clear how much change of $Ca^{2+}$ channel activity in diabetes mellitus (DM) induced hypertension is occurred. We induced DM hypertension in SD rat and compared the $Ca^{2+}$ channel activity with age-matched normotensive SD rat. For inducing DM hypertension, left kidney was removed with 200 gm rat and, after 1 month, 60 mg/kg of streptozotocin was injected into peritoneal space to induce diabetes mellitus. Usually after 4-6 weeks, hypertension was fully induced. For isolating vascular smooth muscle cells (VSMC), we used mesenteric arteriole (3rd - 4th branch of mesenteric artery) of which diameter is below 150 urn. VSMCs were isolated enzymatically. $Ca^{2+}$ current was measured using whole cell patch clamp technique. All experiments were performed at $37^{\circ}C$. The cell membrane area of VSMC of DM hypertensive rat is larger than that of control VSMC($36.6{\pm}3.64{\;}pF{\;}vs{\;}22.4{\pm}1.29{\;}pF, {\;}mean{\pm}S.E.$) When we compared the current amplitude, the $Ca^{2+}$ current amplitude in VSMC of DM hypertensive rat is much larger than that in VSMC of normotensive age-matched rat. After $Ca^{2+}$ current amplitude was normalized by cell membrane area, the current amplitude in DM hypertension is increased to $249.1{\pm}15.9{\;}%{\;}(mean{\pm}S.E.M)$, which means the ;absolute current amplitude is about 4 times larger in DM hypertension. When we compared the steady state activation and inactivation. there were no noticeable differences. From these results. one of cause of the DM hypertension is due to the increase of $Ca^{2+}$ current amplitude. But it need further study why the $Ca^{2+}$ current is so large in VSMC of DM hypertension and how much $Ca^{2+}$ influx through $Ca^{2+}$ channel contribute to the increase of intracellular $Ca^{2+}$ and eventually contribute to development of hypertension.ypertension.

• Journal of Ginseng Research
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• 제29권1호
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• pp.19-26
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• 2005

The last two decades have shown a marked expansion in publications of diverse effects of Panax ginseng. Ginsenosides, as active ingredients of Panax ginseng, are saponins found in only ginseng. Recently, a line of evidences shows that ginsenosides regulate various types of ion channel activity such as $Ca^{2+},\;K^+,\;Na^+,\;Cl^-$, or ligand gated ion channels (i.e. $5-HT_3$, nicotinic acetylcholine, or NMDA receptor) in neuronal, non-neuronal cells, and heterologously expressed cells. Ginsenosides inhibit voltage-dependent $Ca^{2+},\;K^+,\;and\;Na^+$ channels, whereas ginsenosides activate $Ca^{2+}-activated\;Cl^-\;and\;Ca^{2+}-activated\;K^+$ channels. Ginsenosides also inhibit excitatory ligand-gated ion channels such as $5-HT_3$, nicotinic acetylcholine, and NMDA receptors. This review will introduce recent findings on the ginsenoside-induced differential regulations of ion channel activities and will further expand the possibilities how these ginsenoside-induced ion channel regulations are coupled to biological effects of Panax ginseng.

• 동의생리병리학회지
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• 제19권3호
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• pp.743-748
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• 2005

This study was performed for the investigation of vasodilatory efficacy and its underlying mechanisms of Jagumhuan(JGH), a herbal remedy. JGH produced completely endothelium-dependent relaxation and relaxed phenylephrine(PE)-precontracted aorta in a concentration dependent manner. The magnitude of relaxation was greater in PE induced contraction than that of KCl, suggesting involvement of $K^+$ channel in the relaxant effect. Both glibenclamide$(10^{-5}M)$, a $K_{ATP}$ channel inhibitor and indometacin, a cyclooxygenase inhibitor, completely prevented this relaxation. The relaxation effects of JGH, involve in part the release of nitric oxide from the endothelium as pretreatment with L-NAME, an NOS inhibitor, and methylene blue, a cGMP inhibitor, attenuated the responses by 62% and 58%, respectively. In addition, nitrite was produced by JGH in human aortic smooth muscle cells and human umbilical vein endothelial cells. The relaxant effect of JGH was also inhibited by 55.41% by tetraethylammonium(TEA; 5mM), a $K_{Ca}$ channel inhibitor. In the absence of extracellular $Ca^{2+}$, pre-incubation of the aortic rings with JGH significantly reduced the contraction by PE, suggesting that the relaxant action of the JGH includes inhibition of $Ca^{2+}$ release from intracellular stores. These results indicate that in rat thoracic aorta, JGH may induce vasodilation through ATP sensitive $K^+$ channel activation by prostacyclin production. However, the relaxant effect of JGH may also mediated in part by NO pathways and $Ca^{2+}$ activated $K^+$ channel.

• The Korean Journal of Physiology and Pharmacology
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• 제13권5호
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• pp.361-365
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• 2009

Effects of quercetin, a kind of flavonoids, on the vasodilating actions were investigated. Among the mechanisms for quercetin-induced vasodilatation in rat aorta, the involvement with the $Ca^{2+}$ activated $K^+$ ($K_{Ca}$) channel was examined. Pretreatment with NE ($5\;{\mu}M$) or KCl (60 mM) was carried out and then, the modulation by quercetin of the constriction was examined using rat aorta ring strips (3 mm) at $36.5^{\circ}C$. Quercetin (0.1 to $100\;{\mu}M$) relaxed the NE-induced vasoconstrictions in a concentrationdependent manner. NO synthesis (NOS) inhibitor, NG-monomethyl-L-arginine acetate (L-NMMA), at $100\;{\mu}M$ reduced the quercetin ($100\;{\mu}M$)-induced vasodilatation from $97.8{\pm}3.7%$ (n=10) to $78.0{\pm}11.6%$ (n=5, p<0.05). Another NOS inhibitor, L-NG-nitro arginine methyl ester (L-NAME), at $10\;{\mu}M$ also had the similar effect. In the presence of both $100\;{\mu}M$ L-NMMA and $10\;{\mu}M$ indomethacin, the quercetin-induced vasodilatation was further attenuated by $100\;{\mu}M$ tetraethylammonium (TEA, a $K_{Ca}$ channel inhibitor). Also TEA decreased the quercetin-induced vasodilatation in endothelium-denuded rat aorta. Used other $K_{Ca}$ channel inhibitors, the quercetin-induced vasodilatation was attenuated by $0.3\;{\mu}M$ apamin (a SK channel inhibitor), but not by 30 nM charybdotoxin (a BK and IK channel inhibitor). Quercetin caused a concentration-dependent vasodilatation, due to the endotheliumdependent and -independent actions. Also quercetin contributes to the vasodilatation selectively with SK channel on smooth muscle.

• 대한수의학회지
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• 제41권4호
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• pp.485-495
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• 2001

It was investigated whether $Ca^{2+}$ and $K^+$ channels were involved in the inhibitory action of nitric oxide (NO) on the contractile and slow wave activity of guinea pig gastric antral circular muscle. The gastric antral circular muscle showed spontaneous phasic contraction and slow wave. NO donors, 3-morpholinosydnonimine hydrochloride (SIN-1, $0.01{\sim}100{\mu}M$) and S-nitroso-L-cysteine (CysNO, $0.001{\sim}10{\mu}M$), reduced not only the amplitude of phasic contraction but also that of slow wave in a concentration-dependent manner. Both the perfusion of $Ca^{2+}$-free solution and the administration of $Ni^{2+}$, a nonselective $Ca^{2+}$ channel blocker, reduced the phasic contraction as well as the amplitude and frequency of the slow wave. The effects of these treatments were similar to those of NO donors. Nifedipine ($10{\mu}M$), a specific L-type $Ca^{2+}$ channel blocker, abolished the phasic contraction and remarkably reduced the plateau of slow wave but had no profound effect on the upstroke of slow wave. In the whole-cell patch clamp mode, CysNO shifted the steady-state activation curve for L-type $Ca^{2+}$ current to the right and the steady-state inactivation curve to the left. Pretreatment of various $K^+$ channel blockers such as tetraethylammonium (1 mM), 4-aminopyridine (0.5 mM), glibenclamide (10 mM), apamin ($0.1{\mu}M$), and iberiotoxin ($0.1{\mu}M$) did not affect the inhibitory action of SIN-1. These results suggest that NO donors suppress mechanical and electrical activity of guinea pig gastric antral circular muscle by inhibition of L-type $Ca^{2+}$ channel rather than by activation of $K^+$ channels.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권2호
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• pp.629-648
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• 2012

Given a video stream delivering system deployed on a multicast tree, which is embedded in a multi-channel multi-radio wireless mesh network, our problem is concerned about how to allocate interference-free channels to tree links and maximize the number of serviced mesh clients at the same time. In this paper, we propose a channel allocation heuristic algorithm based on best-first search and backtracking techniques. The experimental results show that our BFB based CA algorithm outperforms previous methods such as DFS and BFS based CA methods. This superiority is due to the backtracking technique used in BFB approach. It allows previous channel-allocated links to have feasibility to select the other eligible channels when no conflict-free channel can be found for the current link during the CA process. In addition to that, we also propose a tree refinement method to enhance the quality of channel-allocated trees by adding uncovered destinations at the cost of deletion of some covered destinations. Our aim of this refinement is to increase the number of serviced mesh clients. According to our simulation results, it is proved to be an effective method for improving multicast trees produced by BFB, BFS and DFS CA algorithms.

• BMB Reports
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• 제40권3호
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• pp.302-314
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• 2007

N type calcium channels (CaV2.2) play a key role in the gating of transmitter release at presynaptic nerve terminals. These channels are generally regarded as parts of a multimolecular complex that can modulate their open probability and ensure their location near the vesicle docking and fusion sites. However, the proteins that comprise this component remain poorly characterized. We have carried out the first open screen of presynaptic CaV2.2 complex members by an antibody-mediated capture of the channel from purified rat brain synaptosome lysate followed by mass spectroscopy. 589 unique peptides resulted in a high confidence match of 104 total proteins and 40 synaptosome proteome proteins. This screen identified several known CaV2.2 interacting proteins including syntaxin 1, VAMP, protein phosphatase 2A, $G_{o\alpha}$, G$\beta$ and spectrin and also a number of novel proteins, including clathrin, adaptin, dynamin, dynein, NSF and actin. The unexpected proteins were classified within a number of functional classes that include exocytosis, endocytosis, cytoplasmic matrix, modulators, chaperones, and cell-signaling molecules and this list was contrasted to previous reports that catalogue the synaptosome proteome. The failure to detect any postsynaptic density proteins suggests that the channel itself does not exhibit stable trans-synaptic attachments. Our results suggest that the channel is anchored to a cytoplasmic matrix related to the previously described particle web.