• The Korean Journal of Physiology and Pharmacology
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• v.9 no.4
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• pp.223-230
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• 2005

The purpose of the present study was to examine the effect of naltrexone, an opioid antagonist, on secretion of catecholamines (CA) evoked by cholinergic nicotinic stimulation and membrane-depolarization from the isolated perfused rat adrenal gland and to establish the mechanism of its action. Naltrexone $(3{\times}10^{-6}M)$ perfused into an adrenal vein for 60 min produced time-dependent inhibition in CA secretory responses evoked by ACh $(5.32{\times}10^{-3}M)$ , high $K^+$ $(5.6{\times}10^{-2}M)$ , DMPP ($10^{-4}$ M) and McN-A-343 $(10^{-4}M)$ . Naltrexone itself did also fail to affect basal CA output. In adrenal glands loaded with naltrexone $(3{\times}10^{-6}M)$ , the CA secretory responses evoked by Bay-K-8644, an activator of L-type $Ca^{2+}$ channels and cyclopiazonic acid, an inhibitor of cytoplasmic $Ca^{2+}-ATPase$, were also inhibited. However, in the presence of met-enkephalin $(5{\times}10^{-6}M)$ , a well-known opioid agonist, the CA secretory responses evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were also significantly inhibited. Collectively, these experimental results demonstrate that naltrexone inhibits greatly CA secretion evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors as well as that by membrane depolarization. It seems that this inhibitory effect of naltrexone does not involve opioid receptors, but might be mediated by blocking both the calcium influx into the rat adrenal medullary chromaffin cells and the uptake of $Ca^{2+}$ into the cytoplasmic calcium store, which are at least partly relevant to the direct interaction with the nicotinic receptor itself.

• Archives of Pharmacal Research
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• v.28 no.6
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• pp.699-708
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• 2005

The present study was designed to investigate the effect of naloxone, a well known opioid antagonist, on the secretion of catecholamines (CA) evoked by cholinergic stimulation and membrane-depolarization in the isolated perfused rat adrenal glands, and to establish its mechanism of action. Naloxone ($10^{-6}\~10^{-5}$ M), perfused into an adrenal vein for 60 min, produced dose- and time-dependent inhibition of CA secretory responses evoked by ACh ($5.32\times10^{-3}$ M), high K+ ($5.6\times10^{-2}$ M), DMPP ($10^{-4}$ M) and McN-A-343 ($10^{-4}$ M). Naloxone itself also failed to affect the basal CA output. In adrenal glands loaded with naloxone ($3\times10^{-6}$ M), the CA secretory responses evoked by Bay-K-8644, an activator of L-type $Ca^{2+}$ channels, and cyclopiazonic acid, an inhibitor of cytoplasmic $Ca^{2+}$-ATPase, were also inhibited. In the presence of met-enkephalin ($5\times10^{-6}$ M), a well known opioid agonist, the CA secretory responses evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were also significantly inhibited. Taken together, these results suggest that naloxone greatly inhibits the CA secretion evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors as well as that by membrane depolarization. It seems that these inhibitory effects of naloxone does not involve opioid receptors, but might be mediated by blocking both the calcium influx into the rat adrenal medullary chromaffin cells and the uptake of $Ca^{2+}$ into the cytoplasmic calcium store, which are at least partly relevant to the direct interaction with the nicotinic receptor itself.

• Progress in Medical Physics
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• v.8 no.1
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• pp.3-15
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• 1997

Adrenal chromaffin cells secrete catecholamine in response to acetylcholine. The secretory response has absolute requirement for extracellular calcium, indication that $Ca^{2+}$ influx through voltage dependent $Ca^{2+}$ channel (VDCC) is the primary trigger of the secretion cascade. Although the existence of various types of $Ca^{2+}$ channels has been explored using patch clamp technique in adrenal chromaffin cells, the contribution of different types of $Ca^{2+}$ channels to catecholamine secretion remains to be established. To investigate the quantative contribution of different types of $Ca^{2+}$ channels to cate-cholamine secretion, $Ca^{2+}$ current($I_{Ca}$) and the resultant membrane capacitance increment($\Delta{C}_{m}$) were simultaneoulsy measured. Software based phasor detector technique was used to monitor $\Delta{C}_{m}$. After blockade of L type VDCC with nicardipine (1$\mu$M), $I_{ca}$ was blocked to 43.85$\pm$6.72%(mean$\pm$SEM) of control and the resultant ㅿC$_{m}$ was reduced ot 30.10$\pm$16.44% of control. In the presence of nicardipine and $\omega$-conotoxin in GVIA(l$\mu$M), an N type VDCC antagonist, $I_{ca}$ was blocked to 11.62$\pm$2.96% of control and the resultant $\Delta{C}_{m}$ was reduced to 26.13$\pm$8.25% of control. Finally, in the presence of L, N, and P type $Ca^{2\pm}$ channel antagonists(nicardipine, $\omega$-Conotoxin GVIA, and $\omega$-agatoxin IVA, respectively), $I_{ca}$ and resultant $\Delta{C}_{m}$ were almost completely blocked. From the observation of parallel effects of $Ca^{2+}$ channel antagonists on $I_{ca}$ and $\Delta{C}_{m}$, it was concluded that L, N, and also P type $Ca^{2+}$ channels served and $Ca^{2+}$ source for exocytosis and no difference was observed in their efficiency to evoke exocytosis amost L, N, and P type $Ca^{2+}$ channels.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.1
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• pp.19-27
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• 1999

Apoptosis has been implicated in the pathophysiological mechanisms of various neurodegenerative diseases. In a variety of cell types, oxidative stress has been demonstrated to play an important role in the apoptotic cell death. However, the exact mechanism of oxidative stress-induced apoptosis in neuronal cells is not known. In this study, we induced oxidative stress in IMR-32 human neuroblastoma cells with tert- butylhydroperoxide (TBHP), which was confirmed by significantly reduced glutathione content and glutathione reductase activity, and increased glutathione peroxidase activity. TBHP induced decrease in cell viability and increase in DNA fragmentation, a hallmark of apoptosis, in a dose-dependent manner. TBHP also induced a sustained increase in intracellular $Ca^{2+}$ concentration, which was completely prevented either by EGTA, an extracellular $Ca^{2+}$ chelator or by flufenamic acid (FA), a non-selective cation channel (NSCC) blocker. These results indicate that the TBHP-induced intracellular $Ca^{2+}$ increase may be due to $Ca^{2+}$ influx through the activation of NSCCs. In addition, treatment with either an intracellular $Ca^{2+}$ chelator (BAPTA/AM) or FA significantly suppressed the TBHP-induced apoptosis. Moreover, TBHP increased the expression of p53 gene but decreased c-myc gene expression. Taken together, these results suggest that the oxidative stress-induced apoptosis in neuronal cells may be mediated through the activation of intracellular $Ca^{2+}$ signals and altered expression of p53 and c-myc.

• Journal of Physiology & Pathology in Korean Medicine
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• v.18 no.5
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• pp.1391-1396
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• 2004

The purpose of this research was to investigate the effects of supercritical fluid extract of Kamichungbieum (SFE) on immune reaction. SFE did not affect the subpopulation of murine splenocytes and increased the production of interleukin-2 in serum. Also, SFE inhibited the influx of Ca/sup 2+/ into mast cells and the release of histamine from mast cells. Furthermore, SFE decreased the phagocytic activity of murine macrophages, These results indicate that SFE may be useful for the treatment of allergy related disease via inhibition of histamine release from mast cells and decrease of phagocytic activity of murine macrophages.

• Molecules and Cells
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• v.43 no.1
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• pp.66-75
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• 2020

Saturated fatty acids contribute to β-cell dysfunction in the onset of type 2 diabetes mellitus. Cellular responses to lipotoxicity include oxidative stress, endoplasmic reticulum (ER) stress, and blockage of autophagy. Palmitate induces ER Ca²⁺ depletion followed by notable store-operated Ca²⁺ entry. Subsequent elevation of cytosolic Ca²⁺ can activate undesirable signaling pathways culminating in cell death. Mitochondrial Ca²⁺ uniporter (MCU) is the major route for Ca²⁺ uptake into the matrix and couples metabolism with insulin secretion. However, it has been unclear whether mitochondrial Ca²⁺ uptake plays a protective role or contributes to lipotoxicity. Here, we observed palmitate upregulated MCU protein expression in a mouse clonal β-cell, MIN6, under normal glucose, but not high glucose medium. Palmitate elevated baseline cytosolic Ca²⁺ concentration ([Ca²⁺]_i) and reduced depolarization-triggered Ca²⁺ influx likely due to the inactivation of voltage-gated Ca²⁺ channels (VGCCs). Targeted reduction of MCU expression using RNA interference abolished mitochondrial superoxide production but exacerbated palmitate-induced [Ca²⁺]_i overload. Consequently, MCU knockdown aggravated blockage of autophagic degradation. In contrast, co-treatment with verapamil, a VGCC inhibitor, prevented palmitate-induced basal [Ca²⁺]_i elevation and defective [Ca²⁺]_i transients. Extracellular Ca²⁺ chelation as well as VGCC inhibitors effectively rescued autophagy defects and cytotoxicity. These observations suggest enhanced mitochondrial Ca²⁺ uptake via MCU upregulation is a mechanism by which pancreatic β-cells are able to alleviate cytosolic Ca²⁺ overload and its detrimental consequences.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.6
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• pp.591-598
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• 2017

Propofol is known to cause vasorelaxation of several systemic vascular beds. However, its effect on the pulmonary vasculature remains controversial. In the present study, we investigated the effects of propofol on human pulmonary arteries obtained from patients who had undergone surgery. Arterial rings were mounted in a Multi-Myograph system for measurement of isometric forces. U46619 was used to induce sustained contraction of the intrapulmonary arteries, and propofol was then applied (in increments from $10-300{\mu}m$). Arteries denuded of endothelium, preincubated or not with indomethacin, were used to investigate the effects of propofol on isolated arteries. Propofol exhibited a bifunctional effect on isolated human pulmonary arteries contracted by U46619, evoking constriction at low concentrations ($10-100{\mu}m$) followed by secondary relaxation (at $100-300{\mu}m$). The extent of constriction induced by propofol was higher in an endothelium-denuded group than in an endothelium-intact group. Preincubation with indomethacin abolished constriction and potentiated relaxation. The maximal relaxation was greater in the endothelium-intact than the endothelium-denuded group. Propofol also suppressed $CaCl_2$-induced constriction in the 60 mM $K^+$-containing $Ca^{2+}$-free solution in a dose-dependent manner. Fluorescent imaging of $Ca^{2+}$ using fluo-4 showed that a 10 min incubation with propofol ($10-300{\mu}m$) inhibited the $Ca^{2+}$ influx into human pulmonary arterial smooth muscle cells induced by a 60 mM $K^+$-containing $Ca^{2+}$-free solution. In conclusion, propofol-induced arterial constriction appears to involve prostaglandin production by cyclooxygenase in pulmonary artery smooth muscle cells and the relaxation depends in part on endothelial function, principally on the inhibition of calcium influx through L-type voltage-operated calcium channels.

• The Korean Journal of Physiology
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• v.26 no.1
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• pp.45-54
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• 1992

Effects of pH, $PCO_2$, and adenosine on the vascular contractility were investigated in the pig coronary arteries. The helical strips of isolated coronary arteries were immersed in the HEPES or $HCO_3^-/CO_2$-buffered Tyrode's solution equilibrated with 100% $O_2\;or\;95%\;O_2-5%\;CO_2\;at\;35^{\circ}C$. The contraction was recorded isometrically using a force transducer. The amplitudes of contraction induced by ACh, high $K^+$, and electrical Held stimulation (EFS) were decreased by elevating extracellular pH (pHo) and were increased by lowering pHo. A shift from $0%\;CO_2\;to\;5%\;CO_2$ at constant pHo (pH 7.4) reduced the contractions induced by ACh, high $K^+$, EFS. However the contraction induced by 100mM $K^+$ was less influenced by the change of pHo or $CO_2$. The contraction induced by ACh in $Ca^{2+}$free Tyrode's solution as well as the contraction developed by the addition of extracellular of $Ca^{2+}$ were decreased by lowering pHo and were increased by elevating pHo. High $K^+$ (25mM) induced contraction at pH 6.8 was not returned to the level of the contraction at pH 7.4 by the elevation of extracellular. calcium $[Ca^{2+}]_o$. Adenosine-induced relaxation was more significant with 5% $CO_2$ than 0% $CO_2$ in the high $K^+$-induced contraction and was more significant with low pHo than high pHo in the contraction induced by EFS. From the above results, it is suggested that $H^+$ and $CO_2$ inhibit $Ca^{2+}$ influx as well as $Ca^{2+}$ release from intracellular $Ca^{2+}$ storage sites and enhance the relaxing effect of adenosine in the pig coronary artery.

• Progress in Medical Physics
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• v.12 no.1
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• pp.59-70
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• 2001

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 is the primary trigger of the secretion cascade. Although the existence of various types of $Ca^{2+}$ channels has been explored using patch clamp technique in adrenal chromaffin cells, there is still disagreement with the types of $Ca^{2+}$ channels existed in different species. Therefore, we have tried to identify several distinct types of $Ca^{2+}$ channels in rat chromaffin cells. By using nicardipine(L type channel blocker), $\omega$-CgTx GVIA(N type channel blocker), and $\omega$-AgaTx VIA(P type channel blocker), it was identified that L, N, and P type $Ca^{2+}$ channel exist in rat adrenal chromaffin cells and the order of contribution of each channel type to whole cell $Ca^{2+}$ current was L type> N type> P type. type> P type.

• Archives of Pharmacal Research
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• v.25 no.4
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• pp.511-521
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• 2002

The purpose of this study was to determine whether bromocriptine affects the catecholamines (CA) secretion evoked in isolated perfused rat adrenal glands, by cholinergic stimulation, membrane depolarization and calcium mobilization, and to establish the mechanism of its action. The perfusion of bromocriptine ($1~10{\;}{\mu}M$) into an adrenal vein, for 60 min, produced relatively dose-dependent inhibition in the secretion of catecholamines (CA) evoked by acetylcholine (ACh, 5.32 mM), DMPP ($100{\;}{\mu}M$ for 2 min), McN-A-343 ($100{\;}{\mu}M$ for 2 min), cyclopiazonic acid (CPA, $10{\;}{\mu}M$ for 4 min) and Bay-K-8644 ($10{\;}{\mu}M$ for 4 min). High $K^+$ (56 mM)-evoked CA release was also inhibited, although not in a dose-dependent fashion. Also, in the presence of apomorphine ($100{\;}{\mu}M$), which is also known to be a selective $D_2$-agonist, the CA secretory responses evoked by ACh, high potassium, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were also significantly depressed. However, in adrenal glands preloaded with bromocriptine ($3{\;}{\mu}M$) in the presence of metoclopramide ($15{\;}{\mu}M$), a selective $D_2$-antagonist, the CA secretory responses evoked by ACh, high potassium, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid considerably recovered as compared to that of bromocriptine only. Taken together, these results suggest that bromocriptine can inhibit the CA secretion evoked by stimulation of cholinergic receptors, as well as by membrane depolarization, in the perfused rat adrenal medulla. It is thought this inhibitory effect of bromocriptine may be mediated by inhibiting the influx of extracellular calcium and the release from intracellular calcium stores, through the activation of dopaminergic $D_2$-receptors located in the rat adrenomedullary chromaffin cells. Furthermore, these findings also suggest that the dopaminergic $D_2$-receptors may play an important role in regulating adrenomedullary CA secretion.