• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.81-81
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• 2003

Glibenclamide, a sulfonylurea derivative, has been used in tile treatment of type II diabetes mellitus. Recent studies provided evidence that glibenclamide, in addition to blocking ATP-sensitive $K^{+}$ channels, also affected Na$^{+}$-K$^{+}$ pumps and L-type $Ca^{2+}$ channels in noncardiac cells. The effect of glibenclamide on the cardiac muscle is not clearly known. In the present study, the effects of glibenclamide on intracellular Na$^{+}$ concentration ([Na$^{+}$]$_{i}$ ), twitch tension, $Ca^{2+}$ transient, and membrane potential were investigated in isolated guinea-pig ventricular myocytes. Glibenclamide at concentration of 200 $\mu$M increased [Na$^{+}$]$_{i}$ by 3.9$\pm$0.4 mM (mean $\pm$ SE, n=12), decreased twitch tension by 36.1 $\pm$ 4.0％ (mean $\pm$ SE, n=8), reduced $Ca^{2+}$ transient by 24.4$\pm$5.1％ (mean $\pm$ SE, n=3), slightly depolarized diastolic membrane potential, and did not change action potential duration. To determine whether inhibitions of Na$^{+}$-K$^{+}$ pumps and L-type $Ca^{2+}$ channels are responsible for the increase of [Na$^{+}$]$_{i}$ and the decrease of twitch tension, we tested effects of glibenclamide on Na$^{+}$-K$^{+}$ pump current and L-type $Ca^{2+}$ current. Glibenclamide decreased Na$^{+}$-K$^{+}$ pump current and L-type $Ca^{2+}$ current in a concentration-dependent manner.t in a concentration-dependent manner.

• The Korean Journal of Physiology and Pharmacology
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• v.24 no.3
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• pp.277-286
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• 2020

Polycystic kidney disease 2-like-1 (PKD2L1), also known as polycystin-L or TRPP3, is a non-selective cation channel that regulates intracellular calcium concentration. Calmodulin (CaM) is a calcium binding protein, consisting of N-lobe and C-lobe with two calcium binding EF-hands in each lobe. In previous study, we confirmed that CaM is associated with desensitization of PKD2L1 and that CaM N-lobe and PKD2L1 EF-hand specifically are involved. However, the CaM-binding domain (CaMBD) and its inhibitory mechanism of PKD2L1 have not been identified. In order to identify CaM-binding anchor residue of PKD2L1, single mutants of putative CaMBD and EF-hand deletion mutants were generated. The current changes of the mutants were recorded with whole-cell patch clamp. The calmidazolium (CMZ), a calmodulin inhibitor, was used under different concentrations of intracellular. Among the mutants that showed similar or higher basal currents with that of the PKD2L1 wild type, L593A showed little change in current induced by CMZ. Co-expression of L593A with CaM attenuated the inhibitory effect of PKD2L1 by CaM. In the previous study it was inferred that CaM C-lobe inhibits channels by binding to PKD2L1 at 16 nM calcium concentration and CaM N-lobe at 100 nM. Based on the results at 16 nM calcium concentration condition, this study suggests that CaM C-lobe binds to Leu-593, which can be a CaM C-lobe anchor residue, to regulate channel activity. Taken together, our results provide a model for the regulation of PKD2L1 channel activity by CaM.

• The Korean Journal of Physiology and Pharmacology
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• v.7 no.2
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• pp.53-57
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• 2003

The glutamate receptors (GluRs) are key receptors for modulatory synaptic events in the central nervous system. It has been reported that glutamate increases the intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) and induces cytotoxicity. In the present study, we investigated whether the glutamate-induced $[Ca^{2+}]_i$ increase was associated with the activation of ionotropic (iGluR) and metabotropic GluRs (mGluR) in substantia gelatinosa neurons, using spinal cord slice of juvenile rats (10${\sim}21 day). $[Ca^{2+}]_i$ was measured using conventional imaging techniques, which was combined with whole-cell patch clamp recording by incorporating fura-2 in the patch pipette. At physiological concentration of extracellular $Ca^{2+}$, the inward current and $[Ca^{2+}]_i$ increase were induced by membrane depolarization and application of glutamate. Dose-response relationship with glutamate was observed in both $Ca^{2+}$ signal and inward current. The glutamate-induced $[Ca^{2+}]_i$ increase at holding potential of -70 mV was blocked by CNQX, an AMPA receptor blocker, but not by AP-5, a NMDA receptor blocker. The glutamate-induced $[Ca^{2+}]_i$ increase in $Ca^{2+}$ free condition was not affected by iGluR blockers. A selective mGluR (group I) agonist, RS-3,5-dihydroxyphenylglycine (DHPG), induced $[Ca^{2+}]_i$ increase at holding potential of -70 mV in SG neurons. These findings suggest that the glutamate-induced $[Ca^{2+}]_i$ increase is associated with AMPA-sensitive iGluR and group I mGluR in SG neurons of rats.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.2
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• pp.177-181
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• 2015

The subfornical organ (SFO) is one of circumventricular organs characterized by the lack of a normal blood brain barrier. The SFO neurons are exposed to circulating glutamate ($60{\sim}100{\mu}M$), which may cause excitotoxicity in the central nervous system. However, it remains unclear how SFO neurons are protected from excitotoxicity caused by circulating glutamate. In this study, we compared the glutamate-induced whole cell currents in SFO neurons to those in hippocampal CA1 neurons using the patch clamp technique in brain slice. Glutamate ($100{\mu}M$) induced an inward current in both SFO and hippocampal CA1 neurons. The density of glutamate-induced current in SFO neurons was significantly smaller than that in hippocampal CA1 neurons (0.55 vs. 2.07 pA/pF, p<0.05). To further identify the subtype of the glutamate receptors involved, the whole cell currents induced by selective agonists were then compared. The current densities induced by AMPA (0.45 pA/pF) and kainate (0.83 pA/pF), non-NMDA glutamate receptor agonists in SFO neurons were also smaller than those in hippocampal CA1 neurons (2.44 pA/pF for AMPA, p<0.05; 2.34 pA/pF for kainate, p< 0.05). However, the current density by NMDA in SFO neurons was not significantly different from that of hippocampal CA1 neurons (1.58 vs. 1.47 pA/pF, p>0.05). These results demonstrate that glutamate-mediated action through non-NMDA glutamate receptors in SFO neurons is smaller than that of hippocampal CA1 neurons, suggesting a possible protection mechanism from excitotoxicity by circulating glutamate in SFO neurons.

• Journal of the Semiconductor & Display Technology
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• v.5 no.4 s.17
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• pp.5-9
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• 2006

The SCT thin films are deposited on Pt-coated electrode($Pt/TiN/SiO_2/Si$) using RF sputtering method with Sr/Ca ratio. The maximum grain of thin films is obtained by ratio of Ca at 15 mol%. The dielectric constant was increased with increasing the ratio of Ca, while it was decreased if the ratio of Ca exceeded over 15 mol%. The dielectric constant changes almost linearly in temperature ranges of $-80{\sim}+90$. All SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 200 kHz. The current-voltage characteristics of SCT thin films showed the increasing leakage current as the measuring temperature increases.

• Proceedings of the Korean Biophysical Society Conference
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• 1997.07a
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• pp.27-27
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• 1997

The effects of $a_1$-adrenoceptor stimulation on intracellular $Ca^{2+}$ ([C $a^{2+}$]$_{i}$ ) transient, contraction, and L-type $Ca^{2＋}$ current ( $I_{Ca,L}$) were studied in single cells isolated from ventricles of guinea pig hearts. Phenylephrine, $\alpha$$_1$-adrenergic agonist, (5$\times$10$^{-5}$ ~10$^{-4}$ M) produced a biphasic pattern of inotropism： transient negative response (decrease in contraction by 23.9$\pm$2.5% of control) followed by a sustained positive response (increase in contraction by 60.0$\pm$3.4%, mean $\pm$ SD, n=12).(omitted)ted)

• Journal of Microbiology and Biotechnology
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• v.25 no.8
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• pp.1371-1379
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• 2015

The Ca_v1.2 Ca²⁺ channel is essential for cardiac and smooth muscle contractility and many physiological functions. We mutated single, double, and quadruple sites of the four potential Asn (N)-glycosylation sites in the rabbit Ca_v1.2 into Gln (Q) to explore the effects of Nglycosylation. When a single mutant (N124Q, N299Q, N1359Q, or N1410Q) or Ca_v1.2/WT was expressed in Xenopus oocytes, the biophysical properties of single mutants were not significantly different from Ca_v1.2/WT. In comparison, the double mutant N124,299Q showed a positive shift in voltage-dependent gating. Furthermore, the quadruple mutant (QM; N124,299,1359,1410Q) showed a positive shift in voltage-dependent gating as well as a reduction of current. We tagged EGFP to the QM, double mutants, and Ca_v1.2/WT to chase the mechanisms underlying the reduced currents of QM. The surface fluorescence intensity of QM was weaker than that of Ca_v1.2/WT, suggesting that the reduced current of QM arises from its lower surface expression than Ca_v1.2/WT. Tunicamycin treatment of oocytes expressing Ca_v1.2/WT mimicked the effects of the quadruple mutations. These findings suggest that Nglycosylation contributes to the surface expression and voltage-dependent gating of Ca_v1.2.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.76-84
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• 1994

Droplet transfer modes due to welding conditions and the effect of Ca in welding wire on droplet transfer were investigated. Droplet transfer mode in CO$_{2}$ welding was classified into 2 modes, that is, short circuit and globular transfer, with increasing welding current and voltage. With increasing Ca content in wire, repulsive pressure due to vaporization of Ca was considerably increased. In short circuit transfer region, arcing time was increased and droplet transfer cycle was decreased, with increasing Ca content. In globular transfer region, welding condition for globular transfer was lower current region, with increasing Ca content.

• The Korean Journal of Physiology and Pharmacology
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• v.8 no.6
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• pp.335-338
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• 2004

There are numerous studies on transepithelial transports in duct cells including $Cl^-$ and/or $HCO_3^-$. However, studies on transepithelial $K^+$ transport of normal duct cells in exocrine glands are scarce. In the present study, we examined the characteristics of $K^+$ currents in single duct cells isolated from guinea pig pancreas, using a whole-cell patch clamp technique. Both $Cl^-$ and $K^+$ conductance were found with KCI rich pipette solutions. When the bath solution was changed to low $Cl^-$, reversal potentials shifted to the negative side, $-75{\pm}4\;mV$, suggesting that this current is dominantly selective to $K^+$. We then characterized this outward rectifying $K^+$ current and examined its $Ca^{2+}$ dependency. The $K^+$ currents were activated by intracellular $Ca^{2+}$. 100 nM or 500 nM $Ca^{2+}$ in pipette significantly (P<0.05) increased outward currents (currents were normalized, $76.8{\pm}7.9\;pA$, n=4 or $107.9{\pm}35.5\;pA$, n=6) at +100 mV membrane potential, compared to those with 0 nM $Ca^{2+}$ in pipette $(27.8{\pm}3.7\;pA,\;n=6)$. We next examined whether this $K^+$ current, recorded with 100 nM $Ca^{2+}$ in pipette, was inhibited by various inhibitors, including $Ba^{2+}$, TEA and iberiotoxin. The currents were inhibited by $40.4{\pm}%$ (n=3), $87.0{\pm}%$ (n=5) and $82.5{\pm}%$ (n=9) by 1 mM $Ba^{2+}$, 5 mM TEA and 100 nM iberiotoxin, respectively. Particularly, an almost complete inhibition of the current by 100 nM iberiotoxin further confirmed that this current was activated by intracellular $Ca^{2+}$. The $K^+$ current may play a role in secretory process, slnce recycling of $K^+$ is critical for the initiation and sustaining of $CI^-$ or $HCO_3^-$ secretion in these cells.

• The Korean Journal of Physiology and Pharmacology
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• v.5 no.5
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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.