• The Korean Journal of Physiology and Pharmacology
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• v.2 no.4
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• pp.427-433
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• 1998

In brain hypoxic-ischemia, an excess release of glutamate and a marked production of reactive oxygen species (ROS) occur in neuronal and non-neuronal cells. The present study investigated the effect of the biological antioxidants dihydrolipoic acid (DHLA) and lipoic acid (LA) on N-methyl-D-aspartate (NMDA)- and ROS-induced neurotoxicity in cultured rat cortical neurons. DHLA enhanced NMDA-evoked rises in intracellular calcium concentration ($[Ca^{2+}]_i$). In contrast, LA did not alter the NMDA-evoked calcium responses but decreased after a brief treatment of dithiothreitol (DTT), which possesses a strong reducing potential. Despite the modulation of NMDA receptor-mediated rises in $[Ca^{2+}]_i$, neither DHLA nor LA altered the NMDA receptor-mediated neurotoxicity, as assessed by measuring the amount of lactate dehydrogenase released from dead or injured cells. DHLA, but not LA, prevented the neurotoxicity induced by xanthine/xanthine oxidase-generated superoxide radicals. Both DHLA and LA decreased the glutathione depletion-induced neurotoxicity. The present data may indicate that biological antioxidants DHLA and LA protect neurons from ischemic injuries via scavenging oxygen free radicals rather than modulating the redox modulatory site(s) of NMDA receptor.

• Journal of Ginseng Research
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• v.20 no.2
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• pp.133-138
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• 1996

Rabbit corpus cavernosal smooth muscle strips submaximally precontracted with phenylephrine (5$\times$$10^6$ M) and treated with increasing concentrations of Korean ginseng (1, 5, 10, 20, 30, 40 mg/ml) showed tension decrease concentration-dependently (1 mg/ml: 1.7%, 5 mg/ml: 10.2%, 10 mg/ml: 22.7%, 20 mg/ml: 44.0%, 30 mg/ml: 65.2%, 40 mg/ml: 95.6%). Relaxations to Korean ginseng were inhibited significantly by endothelial disruption, by pretreatment with methylene blue, pyrogallol, L-NNA and atropine. Pretreatment of the muscle strips with ginseng caused concentration-related inhibition of a phenylephrine induced contraction, and in calcium-free high potassium depolarizing solution, decreased basal tension as well as inhibited contraction induced by Caclr. Korean ginseng also produced the reduction of responses to depolarizing medium(50, 40, 60 mM KCI). With these results we can confirm the relaxation effect of ginseng at a dose dependent on the cavernosal smooth muscle and suggest that its action is mediated by multiple action mechanisms that include increasing the release of nitric oxide from the corporal sinusoids. Increasing intracellular calcium sequestration, and a hyperpolarizating action.

• The Korean Journal of Physiology
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• v.24 no.2
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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.

• Development and Reproduction
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• v.24 no.4
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• pp.297-306
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• 2020

Repetitive changes in the intracellular calcium concentration ([Ca²⁺]i) triggers egg activation, including cortical granule exocytosis, resumption of second meiosis, block to polyspermy, and initiating embryonic development. [Ca²⁺]i oscillations that continue for several hours, are required for the early events of egg activation and possibly connected to further development to the blastocyst stage. The sources of Ca²⁺ ion elevation during [Ca²⁺]i oscillations are Ca²⁺ release from endoplasmic reticulum through inositol 1,4,5 tri-phosphate receptor and Ca²⁺ ion influx through Ca²⁺ channel on the plasma membrane. Ca²⁺ channels have been characterized into voltage-dependent Ca²⁺ channels (VDCCs), ligand-gated Ca²⁺ channel, and leak-channel. VDCCs expressed on muscle cell or neuron is specified into L, T, N, P, Q, and R type VDCs by their activation threshold or their sensitivity to peptide toxins isolated from cone snails and spiders. The present study was aimed to investigate the localization pattern of N and P/Q type voltage-dependent calcium channels in mouse eggs and the role in fertilization. [Ca²⁺]i oscillation was observed in a Ca²⁺ contained medium with sperm factor or adenophostin A injection but disappeared in Ca²⁺ free medium. Ca²⁺ influx was decreased by Lat A. N-VDCC specific inhibitor, ω-Conotoxin CVIIA induced abnormal [Ca²⁺]i oscillation profiles in SrCl₂ treatment. N or P/Q type VDC were distributed on the plasma membrane in cortical cluster form, not in the cytoplasm. Ca²⁺ influx is essential for [Ca²⁺]i oscillation during mammalian fertilization. This Ca²⁺ influx might be controlled through the N or P/Q type VDCCs. Abnormal VDCCs expression of eggs could be tested in fertilization failure or low fertilization eggs in subfertility women.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.6
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• pp.817-824
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• 1997

Extracellular ATP elicits various biological responses and plays a significant role in physiological regulation. Recently, ATP-induced growth inhibitions were reported in some tumor cell lines, but these effects and mechanisms are not well hewn. This study was conducted to investigate ATP-induced growth inhibition in mouse $leukemic(P388D_1)$ cells. ATP inhibited cell growth in a dose-dependent manner as analyzed by MTS assay$(IC_{50}: 33.1\;{\mu}M)$. Nucleotides other than ATP, such as ADP$(37.5;{\mu}M)$ and AMP$(33.2;{\mu}M)$ had the same effects as ATP but adenosine$(57.8;{\mu}M)$ showed less effect than ATP. ATP attenuated the cells in $G_0/G_l\;and\;G_2/M$ phases but increased those in S phase in flow cytometric analysis. Hypodiploid cells$(A_0)$, the presumptive findings of apoptosis, were found among the ATP-treated cells. ATP induced DNA fragmentation into $180{\mu}200\;bps $as measured by electrophoresis. some apoptotic cells were stained by TUNEL method. ATP increased the intracellular free $Ca^{++}$concentration$([Ca^{++}]_i)$ and the increment of $([Ca^{++}]_i)$ was caused by influx from the extracellular space. These results suggest that extracellular ATP induces growth inhibition through apoptosis.

• The Korean Journal of Physiology and Pharmacology
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• v.15 no.1
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• pp.53-59
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• 2011

The secretion of insulin from pancreatic ${\beta}$-cells is triggered by the influx of $Ca^{2+}$ through voltage-dependent $Ca^{2+}$ channels. The resulting elevation of intracellular calcium ($[Ca^{2+}]_i$) triggers additional $Ca^{2+}$ release from internal stores. Less well understood are the mechanisms involved in $Ca^{2+}$ mobilization from internal stores after activation of $Ca^{2+}$ influx. The mobilization process is known as calcium-induced calcium release (CICR). In this study, our goal was to investigate the existence of and the role of caffeine-sensitive ryanodine receptors (RyRs) in a rat pancreatic ${\beta}$-cell line, INS-1 cells. To measure cytosolic and stored $Ca^{2+}$, respectively, cultured INS-1 cells were loaded with fura-2/AM or furaptra/AM. $[Ca^{2+}]_i$ was repetitively increased by caffeine stimulation in normal $Ca^{2+}$ buffer. However, peak $[Ca^{2+}]_i$ was only observed after the first caffeine stimulation in $Ca^{2+}$ free buffer and this increase was markedly blocked by ruthenium red, a RyR blocker. KCl-induced elevations in $[Ca^{2+}]_i$ were reduced by pretreatment with ruthenium red, as well as by depletion of internal $Ca^{2+}$ stores using cyclopiazonic acid (CPA) or caffeine. Caffeine-induced $Ca^{2+}$ mobilization ceased after the internal stores were depleted by carbamylcholine (CCh) or CPA. In permeabilized INS-1 cells,$Ca^{2+}$ release from internal stores was activated by caffeine, $Ca^{2+}$, or ryanodine. Furthermore, ruthenium red completely blocked the CICR response in perrneabilized cells. RyRs were widely distributed throughout the intracellular compartment of INS-1 cells. These results suggest that caffeine-sensitive RyRs exist and modulate the CICR response from internal stores in INS-1 pancreatic ${\beta}$-cells.

• Journal of Society of Preventive Korean Medicine
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• v.11 no.1
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• pp.9-21
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• 2007

This study was performed to evaluate the effect of Carthami tinctorius(HH) on osteoblast function and gene expression. The osteoblasts separated from the rat calvariae were cultivated to evaluate the cell function, and MG-63 cell was also cultivated for the test of mRNA synthesis. In this experiments, cell proliferation of rat calvarial cells was increased by HH. PKC activity, intracellular free calcium level and collgen synthesis from calvarial cells were increased by HH, but not PKA activity. And the mRNA of $PLA_2$, COX-2, and $PGE_2$ synthase from MG-63 were decreased by HH, but the mRNA of prostacyclin synthase was increased. It is concluded that HH might increase the proliferation of calvarial cell resulted from augumentation of osteoblast activity and its mRNA synthesis.

• Nutrition Research and Practice
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• v.12 no.3
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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 ${\beta}-cells$.

• Journal of Medicine and Life Science
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• v.15 no.2
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• pp.67-71
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• 2018

Neuronal excitotoxicity induces mitochondrial dysfunction and the release of proapoptotic proteins. Excitotoxicity, the process by which the overactivation of excitatory neurotransmitter receptors leads to neuronal cell death. Neuronal death by excitotoxicity was related to neuronal degenerative disorders and hypoxia, results from excessive exposure to excitatory neurotransmitters, such as glutamate. Glutamate acts at NMDA receptors in cultured neurons to increase the intracellular free calcium concentration. Therefore endogenous glutamate may be a key factor to regulate neuronal cell death via activating $Ca^{2+}$ signaling. For this issue, we tested some conditions to alter intracellular $Ca^{2+}$ level in dissociated hippocampal neurons of rats. Cultured hippocampal neuron were treated by KCl (20 mM), $CaCl_2$ (3.8 mM) and glutamate ($5{\mu}M$) for 24 hrs. Interestingly, The Optical Density of hippocampal neurons was increased by high KCl application in MTT assay data. This enhanced response by high KCl was dependent on synaptic $Ca^{2+}$ influx but not on intracellular $Ca^{2+}$ level. However, the number of neurons seemed to be not changed in Hoechst 33342 staining data. These results suggest that enhancement of synaptic activity plays a key role to increase mitochondrial signaling in hippocampal neurons.

• The Korean Journal of Physiology and Pharmacology
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• v.14 no.1
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• pp.21-28
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• 2010

Phenolic compounds affect intracellular free $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) signaling. The study examined whether the simple phenolic compound octyl gallate affects ATP-induced $Ca^{2+}$ signaling in PC12 cells using fura-2-based digital $Ca^{2+}$ imaging and whole-cell patch clamping. Treatment with ATP ($100\;{\mu}M$) for 90 s induced increases in $[Ca^{2+}]_i$ in PC12 cells. Pretreatment with octyl gallate (100 nM to $20\;{\mu}M$) for 10 min inhibited the ATP-induced $[Ca^{2+}]_i$ response in a concentration-dependent manner ($IC_{50}=2.84\;{\mu}M$). Treatment with octyl gallate ($3\;{\mu}M$) for 10 min significantly inhibited the ATP-induced response following the removal of extracellular $Ca^{2+}$ with nominally $Ca^{2+}$-free HEPES HBSS or depletion of intracellular $Ca^{2+}$ stores with thapsigargin ($1\;{\mu}M$). Treatment for 10 min with the L-type $Ca^{2+}$ channel antagonist nimodipine ($1\;{\mu}M$) significantly inhibited the ATP-induced $[Ca^{2+}]_i$ increase, and treatment with octyl gallate further inhibited the ATP-induced response. Treatment with octyl gallate significantly inhibited the $[Ca^{2+}]_i$ increase induced by 50 mM KCI. Pretreatment with protein kinase C inhibitors staurosporin (100 nM) and GF109203X (300 nM), or the tyrosine kinase inhibitor genistein ($50\;{\mu}M$) did not significantly affect the inhibitory effects of octyl gallate on the ATP-induced response. Treatment with octyl gallate markedly inhibited the ATP-induced currents. Therefore, we conclude that octyl gallate inhibits ATP-induced $[Ca^{2+}]_i$ increase in PC12 cells by inhibiting both non-selective P2X receptor-mediated influx of $Ca^{2+}$ from extracellular space and P2Y receptor-induced release of $Ca^{2+}$ from intracellular stores in protein kinase-independent manner. In addition, octyl gallate inhibits the ATP-induced $Ca^{2+}$ responses by inhibiting the secondary activation of voltage-gated $Ca^{2+}$ channels.