• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 1996년도 정기총회 및 학술발표회
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• pp.42-42
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• 1996

Adrenal chromaffin cells secrete catecholamine in response to acetylcholine. The secretory response has absolute requirement for extracellular calcium, indicating that $Ca^{2+}$ influx through voltage operated $Ca^{2+}$ channels (VOCC) is the primary trigger of the secretion cascade. Although the existence of various types of $Ca^{2+}$ channels has been explore using patch clamp techique in adrenal chromaffin cells, the contribution of different types of $Ca^{2+}$ channels to catecholamine secretion remains to be establised. (omitted)omitted)

• Animal cells and systems
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• 제15권2호
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• pp.131-138
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• 2011

Redox regulation is one of the ubiquitous mechanisms to modulate ion channels. We here investigated how 5,5'-dithio-bis (2-nitrobenzoic acid), a cysteine specific oxidizing reagent, modulates $Ca_v3.1$ and $Ca_v3.2$ T-type $Ca^{2+}$ channels expressed in Xenopus oocytes. Application of the reagent inhibited $Ca_v3.1$ and $Ca_v3.2$ currents in a dose-dependent manner. The oxidizing reagent (1 mM) reduced the peak amplitude of $Ca_v3.1$ and $Ca_v3.2$ currents by ~50% over 2-3 minutes and the decreased currents were fully recovered upon washout of it. The reagent slowed the activation and inactivation kinetics of $Ca_v3.1$, $Ca_v3.2$, and $Ca_v3.3$ channel currents. Notably, the reagent positively shifted both activation and steady-state inactivation curves of $Ca_v3.1$, while it did not those of $Ca_v3.2$. Utilizing chimeric channels from $Ca_v3.1$ and $Ca_v3.2$, we localized the domains III and IV of $Ca_v3.1$ responsible for the positive shifts of channel activation and steady-state inactivation. These findings provide hints relevant to the electrophysiological and molecular mechanisms accounting for the oxidative regulation of T-type channels.

• 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.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2003년도 정기총회 및 학술발표회
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• pp.38-38
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• 2003

The electrical properties of neurons are produced by the coordinated activity of ion channels (Hille, 1992). $K^{+}$ channels play a key role in shaping action potentials and in determining neural firing patterns. Small conductance $Ca^{2+}$-activated $K^{+}$ (S $K_{Ca}$ ) channels are involved in modulating the slow component of afterhyperpolarization (AHP) (Kohler et al., 1996). Here we examine whether rat type 2 S $K_{Ca}$ (rSK2) channels can affect the shape of the action potential and the neural firing pattern, by overexpressing rat SK2 channels in Aplysia neuron R15. Our results show that rSK2 overexpression decreased the intraburst frequency and changed the regular bursting activity of neurons to an irregular bursting or beating pattern in R15, Furthermore, the overexpression of rSK2 channels increased AHP and reduced the duration of the action potential. Thus, our results suggest that ectopic S $K_{Ca}$ channels play an important role in regulating the filing pattern and the shape of the action potential.ntial.

• 고려인삼학회:학술대회논문집
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• 고려인삼학회 2005년도 창립30주년기념 추계 학술대회 및 정기총회
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• pp.32-40
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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 presentation will introduce recent findings on the ginsenoside-induced differential regulations of ion channel activities as a ligand as other drugs do.

• Journal of Korean Neurosurgical Society
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• 제39권3호
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• pp.215-220
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• 2006

Objective : Tyrosine kinase inhibitors may be useful in the management of cerebral vasospasm. It has not yet been reported whether L-type $Ca^{2+}$ channels playa role in tyrosine kinase inhibitors-induced vascular relaxation of cerebral artery. This study was undertaken to clarify the role of L-type $Ca^{2+}$ channels in tyrosine kinase inhibitors-induced vascular relaxation, and to investigate the effect of tyrosine kinase inhibitors on L-type $Ca^{2+}$ channels currents in freshly isolated smooth muscle cells from rat basilar artery. Methods : The isolation of rat basilar smooth muscle cells was performed by special techniques. The whole cell currents were recorded by whole cell patch clamp technique in freshly isolated smooth muscle cells from rat basilar artery. Results : Patch clamp studies revealed a whole-cell current which resembles the L-type $Ca^{2+}$ current reported by others. The amplitude of this current was decreased by nimodipine and increased by Bay K 8644. Genistein[n=5], tyrphostin A-23[n=3]. A-25[n=6] $30{\mu}M$ reduced the amplitude of the L -type $Ca^{2+}$ channel current in whole cell mode. In contrast, diadzein $30{\mu}M$ [n=3]. inactive analogue of genistein, did not decrease the amplitude of the L-type $Ca^{2+}$ channels current. Conclusion : These results suggest that tyrosine kinase inhibitors such as genistein, tyrphostin A-23, A-25 may relax cerebral vessel through decreasing level of intracellular calcium, [$Ca^{2+}$]i, by inhibition of L-type $Ca^{2+}$ channel.

• Archives of Pharmacal Research
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• 제27권3호
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• pp.305-313
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• 2004

The effect of diazoxide, a $K^{+}$channel opener, on apoptotic cell death was investigated in HepG2 human hepatoblastoma cells. Diazoxide induced apoptosis in a dose-dependent manner and this was evaluated by flow cytometric assays of annexin-V binding and hypodiploid nuclei stained with propidium iodide. Diazoxide did not alter intracellular $K^{+}$concentration, and various inhibitors of $K^{+}$channels had no influence on the diazoxide-induced apoptosis; this implies that $K^{+}$channels activated by diazoxide may be absent in the HepG2 cells. However, diazoxide induced a rapid and sustained increase in intracellular $Ca^{2+}$ concentration, and this was completely inhibited by the extracellular $Ca^{2+}$ chelation with EGTA, but not by blockers of intracellular $Ca^{2+}$ release (dantrolene and TMB-8). This result indicated that the diazoxide-induced increase of intracellular $Ca^{2+}$ might be due to the activation of a Ca2+ influx pathway. Diazoxide-induced $Ca^{2+}$ influx was not significantly inhibited by either voltage-operative $Ca^{2+}$ channel blockers (nifedipinen or verapamil), or by inhibitors of $Na^{+}$, $Ca^{2+}$-exchanger (bepridil and benzamil), but it was inhibited by flufenamic acid (FA), a $Ca^{2+}$-permeable nonselective cation channel blocker. A quantitative analysis of apoptosis by flow cytometry revealed that a treatment with either FA or BAPTA, an intracellular $Ca^{2+}$ chelator, significantly inhibited the diazoxide-induced apoptosis. Taken together, these results suggest that the observed diazoxide-induced apoptosis in the HepG2 cells may result from a $Ca^{2+}$ influx through the activation of $Ca^{2+}$-permeable non-selective cation channels. These results are very significant, and they lead us to further suggest that diazoxide may be valuable for the therapeutic intervention of human hepatomas.

• The Korean Journal of Physiology and Pharmacology
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• 제5권2호
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• pp.139-146
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• 2001

L-type $Ca^{2+}$ channels play an important role in regulating cytosolic $Ca^{2+}$ and thereby regulating hormone secretions in neuroendocrine cells. Since hormone secretions are also regulated by various kinds of protein kinases, we investigated the role of some kinase activators and inhibitors in the regulation of the L-type $Ca^{2+}$ channel currents in rat pituitary $GH_3$ cells using the patch-clamp technique. Phorbol 12,13-dibutyrate (PDBu), a protein kinase C (PKC) activator, and vanadate, a protein tyrosine phosphatase (PTP) inhibitor, increased the $Ba^{2+}$ current through the L-type $Ca^{2+}$ channels. In contrast, bisindolylmaleimide I (BIM I), a PKC inhibitor, and genistein, a protein tyrosine kinase (PTK) inhibitor, suppressed the $Ba^{2+}$ currents. Forskolin, an adenylate cyclase activator, and isobutyl methylxanthine (IBMX), a non-specific phosphodiesterase inhibitor, reduced $Ba^{2+}$ currents. The above results show that the L-type $Ca^{2+}$ channels are activated by PKC and PTK, and inhibited by elevation of cyclic nucleotides such as cAMP. From these results, it is suggested that the regulation of hormone secretion by various kinase activity in $GH_3$ cells may be attributable, at least in part, to their effect on L-type $Ca^{2+}$ channels.

• Animal cells and systems
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• 제3권1호
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• pp.53-58
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• 1999

The immunocytochemical method was used to identify the existence of voltage-dependent $Ca^{2＋}$-channels in mouse follicular oocytes. Three types of voltage-dependent $Ca^{2＋}$-channels were shown to exist in the follicular oocytes for the first time, the P/Q-type $Ca^{2＋}$-channel, the N-type $Ca^{2＋}$-channel, and the L-type $Ca^{2＋}$-channel. Among proven $Ca^{2＋}$-channels distributions of the P/Q-type $Ca^{2＋}$-channel and L-type $Ca^{2＋}$-channel showed localized staining (clustered pattern) on the oolemma. The distribution of the P/Q-type $Ca^{2＋}$-channel showed all localized staining, and the range of localized staining was from 1 to 8 in staining intensity. As the staining intensity increased from 1 to 8, the number of localized staining decreased. The L-type $Ca^{2＋}$-channel are homogeneously stained (29.4%-54.2%), while some of them (around 28.7%-44.1%) showed localized staining on the oolemma. However, the rest of them showed no staining at all (17.1%- 26.5%). On the contrary, the N-type $Ca^{2＋}$-channel showed mostly homogeneous staining, while nonstaining oocytes were around 33.8%. The rest showed localized staining (10%). However, staining intensity was much weaker than those of the P/Q-type and L-type $Ca^{2＋}$-channel. In fact, the N-type $Ca^{2＋}$-channel has been known to exist only in neurons (from ectoderm origin), but it is unknown how the N-type $Ca^{2＋}$-channel exists in the follicular oocytes (from mesoderm origin). Further studies are needed to examine the expression of $Ca^{2＋}$-channels during the developmental stages of the oocytes.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2003년도 정기총회 및 학술발표회
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• pp.23-23
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• 2003

It has been suggested that the impairment of smooth muscle cell (SMC) function by alterations in the $Ca^{2+}$-activated $K^{+}$ ( $K_{Ca}$ ) channels accounts for the reduction in coronary reserve during left ventricular hypertrophy (LVH). However, this hypothesis has not been fully investigated. The main goal of this study was to assess whether the properties of $K_{Ca}$ channels in coronary SMCs were altered during LVH. New Zealand white rabbits (0.8-1.0 kg) and Sprague-Dawley rats (300-400 g) were randomly selected to receive either an injection of isoproterenol (300 $\mu\textrm{g}$/kg body weight) or an equal volume of 0.9％ saline (1 mL/kg body weight). The animals developed LVH 10 days after injection. In patch-clamp experiments, the unitary current amplitude and open probability for the $K_{Ca}$ channels were significantly reduced in LVH patches compared with control patches. The concentration-response curve of the $K_{Ca}$ channel to [C $a^{2+}$]$_{i}$ was shifted to the right. Inhibition of the $K_{Ca}$ channels with TEA was more pronounced in LVH cells than in the control cells. The whole-cell currents of $K_{Ca}$ channels were reduced during LVH. Western blot analysis indicated no differences in $K_{Ca}$ channel expression between the control and LVH coronary SM membranes. In contraction experiments, the effect of a high $K^{+}$concentration on the resting tension of the LVH coronary artery was greater than on that of the control. The effect of TEA on the resting tension of the LVH coronary artery was reduced as compared with the effect on the control. Our findings imply a novel mechanism for reduced coronary reserve during LVH.ing LVH.