• The Korean Journal of Physiology and Pharmacology
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• v.7 no.6
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• pp.375-379
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• 2003

$Ca^{2+}$ influx appears to be important for triggering myoblast fusion. It remains, however, unclear how $Ca^{2+}$ influx rises prior to myoblast fusion. Recently, several studies suggested that NMDA receptors may be involved in $Ca^{2+}$ mobilization of muscle, and that $Ca^{2+}$ influx is mediated by NMDA receptors in C2C12 myoblasts. Here, we report that other types of ionotropic glutamate receptors, non-NMDA receptors (AMPA and KA receptors), are also involved in $Ca^{2+}$ influx in myoblasts. To explore which subtypes of non-NMDA receptors are expressed in C2C12 myogenic cells, RT-PCR was performed, and the results revealed that KA receptor subunits were expressed in both myoblasts and myotubes. However, AMPA receptor was not detected in myoblasts but expressed in myotubes. Using a $Ca^{2+}$ imaging system, $Ca^{2+}$ influx mediated by these receptors was directly measured in a single myoblast cell. Intracellular $Ca^{2+}$ level was increased by KA, but not by AMPA. These results were consistent with RT-PCR data. In addition, KA-induced intracellular $Ca^{2+}$ increase was completely suppressed by treatment of nifedifine, a L-type $Ca^{2+}$ channel blocker. Furthermore, KA stimulated myoblast fusion in a dose-dependent manner. CNQX inhibited not only KA-induced myoblast fusion but also spontaneous myoblast fusion. Therefore, these results suggest that KA receptors are involved in intracellular $Ca^{2+}$ increase in myoblasts and then may play an important role in myoblast fusion.

• The Korean Journal of Physiology
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• v.24 no.1
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• pp.77-90
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• 1990

There have been conflicting reports concerning the effect of Panax ginseng on the contractility of vascular smooth muscle, i.e., Panax ginseng extract has been reported to cause relaxation, contraction or to have no effect on the tension of vascular smooth muscle. A further investigation of $Ca^{++}$ stores which supply $Ca^{++}$ for contraction of vascular smooth muscle is needed to understand the underlying mechanisms of this conflicting effect of ginseng alcohol extract (GAE). The present study was intended to examine the sources of calcium mobilized for contraction of vascular smooth muscle by GAE. Aortic ring preparations were made from the rabbit thoracic aorta and endothelial cells were removed from the ring. The contractility of the aortic ring was measured under various experimental conditions and $Ca^{++}$ flux across the membrane of aortic ring and the sarcoplasmic reticulum and mitochondria were measured with a calcium selective electrode. The result were summarized as follows; 1) At low concentration of extracellular $Ca^{++}$, GAE increased the contractility of vascular smooth muscle in dose-dependent fashion except high concentration $Ca^{++}$ (1 mM). 2) In the presence of ryanodine, GAE still increased contractility of vascular smooth muscle as much as control group, but in the presence of caffeine, GAE increased it significantly. i.e. Their effects seemed to be additive. 3) In the presence of verapamil+lanthanum, and verapamil+lanthanum+ryanodine, the contractility of the vascular smooth muscle was decreased, but a dose dependent increase in vascular tension was still demonstrated by GAE although total tension was low. 4) GAE increased $Ca^{++}$ efflux from vascular smooth muscle cells, but have no effect on $Ca^{++}$ influx. 5) GAE increased $Ca^{++}$ efflux from sarcoplasmic reticulum and mitochondria vesicles. From the above results, it may be concluded that GAE increased the release of $Ca^{++}$ from sarcoplasmic reticulum, mitochondria or other intracellular $Ca^{++}$ stores of vascular smooth muscle, but it does not increase $Ca^{++}$ influx across the plasma membrane.

• International Journal of Oral Biology
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• v.31 no.3
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• pp.99-105
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• 2006

Von Ebner's glands (vEG) are minor salivary glands associated with circumvallate and foliate papilla. The secretions of vEG consist of microenvironment of the taste buds in the circumvallate and foliate papillae, and thus saliva from vEG plays a role in the perception of taste. The $Ca^{2+}$ signaling system in rat vEG acinar cell was examined using the $Ca^{2+}$-sensitive fluorescent indicator Fura-2. Agonist-induced increase in intracellular $Ca^{2+}\;([Ca^{2+}]_i)$ was stimulated by carbachol (CCh) and substance P (SP), but not by norepinephrine (NE), and recovered to control levels by their receptor antagonists dose-dependently. The effects were also observed in $Ca^{2+}$-free medium, suggesting mobilization from intracellular $Ca^{2+}$ store. These results in the vEG acinar cell indicate that 1) $[Ca^{2+}]_i$ is at least regulated by muscarinic and neurokininergic (NK1) receptors; 2) the increases in $[Ca^{2+}])i$ activated by CCh and SP are mainly mediated by discharge of cytosolic calcium pool.

• The Korean Journal of Physiology and Pharmacology
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• v.7 no.6
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• pp.311-316
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• 2003

Endothelins secreted from keratinocytes are intrinsic mitogens and melanogens of human melanocytes in UVB-induced hyperpigmentation. To elucidate the cellular mechanism of antimelanogenic activity of bamboo extract, the effects of three ingredients of bamboo extract on endothelin 1 (ET-1)-induced $Ca^{2+}$ mobilization were investigated in cultured human melanocytes. ET-1 receptors in human melanocytes were characterized by using specific antagonist, and ET-1 was found to increase intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) by activating ET-B receptor. SM709 (1,2-O-diferulyl-glycerol), an ingredient of bamboo extract, inhibited ET-1-induced $[Ca^{2+}]_i$ increase in a concentration- and time-dependent manner, although another ingredients SM707 and SM708 had no effect on ET-1-induced $[Ca^{2+}]_i$ increase in human melanocytes. SM709 ($100{\mu}M$), however, did not affect $[Ca^{2+}]_i$ increase induced by thapsigargin and caffeine, suggesting that SM709 has no effect on the $Ca^{2+}$ store in melanocytes. Furthermore, SM709 did not affect $[Ca^{2+}]_i$ increase induced by LPA or ATP, known as G protein-mediated PLC activators like ET-1. Taken together, it is suggested that SM709 antagonizes ET-1-induced transmembrane signaling through ET-B receptor, which maybe a possible underlying mechanism of antimelanogenic activity of bamboo extract in human melanocytes.

• Toxicological Research
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• v.14 no.4
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• pp.507-513
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• 1998

The purpose of this study was to clarify the effect of silica on cytosolic free calcium mobilization and cell injury in primary cultured rat hepatocytes. Cytosolic free calcium concentration ([Ca$^{2+}$]) was measured employing calcium sensitive fluorescent dye, Fura-2 / AM, and cell injury was evaluated by determination of cellular ATP contents. Silica increased [Ca$^{2+}$], in a concentration-dependent manner in hepatocytes (10$^{-5}$ ~10$^{-2}$ M). Silica caused a biphasic increase in [Ca$^{2+}$], which was composed of an initial rapid rise and following sustained phase. $Ca^{2+}$ removal from the medium resulted in abolishment of initial and sustained phase of silica (10$^{-2}$ M)-induced [Ca$^{2+}$], in hepatocytes. The pretreatment with nifedipine (1 $\mu$M) attenuated silica-induced [Ca$^{2+}$], increases. Silica decreased cellular ATP contents in a dose-dependent manner. This silica-induced cell injury was attenuated by the pretreatment with EGTA (100 $\mu$M) and nifedipine (1 $\mu$M). This study suggests that the elevation of [Ca$^{2+}$], caused by silica may be due mainly to influx through a plasma membrane $Ca^{2+}$ channel and hepatotoxicity by silica relate with alteration of calcium homeostasis.ium homeostasis.

• The Korean Journal of Physiology and Pharmacology
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• v.11 no.1
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• pp.21-30
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• 2007

The present study was designed to establish comparatively the inhibitory effects of cilnidipine(CNP), nifedipine(NIF), and $\omega$-conotoxin GVIA(CTX) on the release of CA evoked by cholinergic stimulation and membrane depolarization from the isolated perfused model of the rat adrenal medulla. CNP(3 ${\mu}M$), NIF(3 ${\mu}M$), and CTX(3 ${\mu}M$) perfused into an adrenal vein for 60 min produced greatly inhibition in CA secretory responses evoked by ACh($5.32{\times}10^{-3}M$), DMPP($10^{-4}M$ for 2 min), McN-A-343($10^{-4}M$ for 2 min), high $K^+(5.6{\times}10^{-2}M)$, Bay-K-8644($10^{-5}M$), and cyclopiazonic acid($10^{-5}M$), respectively. For the CA release evoked by ACh and Bay-K-8644, the following rank order of potency was obtained: CNP>NIF>CTX. The rank order for the CA release evoked by McN-A-343 and cyclopiazonic acid was CNP>NIF>CTX. Also, the rank orders for high $K^+$ and for DMPP were NIF>CTX>CNP and NIF>CNP>CTX, respectively. Taken together, these results demonstrate that all voltage-dependent $Ca^{2+}$ channels(VDCCs) blockers of cilnidipine, nifedipine, and $\omega$-conotoxin GVIA inhibit greatly the CA release evoked by stimulation of cholinergic(both nicotinic and muscarinic) receptors and the membrane depolarization without affecting the basal release from the isolated perfused rat adrenal gland. It seems likely that the inhibitory effects of cilnidipine, nifedipine, and $\omega$-conotoxin GVIA are mediated by the blockade of both L- and N-type, L-type only, and N-type only VDCCs located on the rat adrenomedullary chromaffin cells, respectively, which are relevant to $Ca^{2+}$ mobilization. It is also suggested that N-type VDCCs play an important role in the rat adrenomedullary CA secretion, in addition to L-type VDCCs.

• The Korean Journal of Pharmacology
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• v.8 no.1
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• pp.67-75
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• 1972

Many studies on the mechanism of the inotropic action of cardiac glycosides have shown the possible intimate relationship between the mobilization of intracellular calcium and inotropic effect. Evidence obtained from recent studies suggests that cardiac glycosides may increase the intracellular $Ca^{++}$ concentration through the release of this ion from cellular or intracellular membrane. It seemed imperative to study the effect of ouabain on the interaction between mitochondria and $Ca^{++}$, because mitochondria are known to have a rather powerful $Ca^{++}$ pump mechanism which may have an important role on the regulation of intracellular $Ca^{++}$ concentration. The present investigations was made into the effect of ouabain on $Ca^{++}$ untake of mitochondria in the presence of ATP and its dependence on $K^+$ and $Na^+$ in the medium. The results are summarized as follows: 1. The rate of rise in the turbidity of superprecipitation was solely influenced by ionic strength of the medium, not by the species of ion, i.e. $Na^+$ or $K^+$. The higher ionic strength suppressed and the lower enhanced the rate of superprecipitation respectively. 2. No effect of ouabain was found on the rate of superprecipitation. 3. Mitochondria depressed the rate of superpretipitation, and the depressed rate of superprecipitation by mitochondria was reversed by ouabain, and the degree of this reversal was almost identical in $Na^+$ and $K^+$ medium. 4. $Ca^{++}$ uptake of mitochondria was inhibited by ouabain in the presence of ATP and the degree of inhibition showed the dose-response manner in terms of concentration of ouabain. 5. In the absence of ATP, mitochondria took or the $Ca^{++}$ in initial period but released it later. Such uptake and release of $Ca^{++}$ was not influenced by ouabain. 6. It is suggested that intracellular calcium mobilization by ouabain through the action upon the mitochondria was due to inhibition on ATP-dependent $Ca^{++}$ uptake by this agent, not to the action upon so called binding.

• The Korean Journal of Physiology
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• v.26 no.2
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• pp.129-136
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• 1992

The effects of $Cd^{2+}$ on spontaneous contraction, and the contractures induced by $0mM\;Na^+,\;60mM\;K^+\;and\;10^{-6}\;M$ acetylcholine, 1mM caffeine were studied in order to elucidate diverse actions of $Cd^{2+}$ on the $Ca^{2+}$ mobilization related with contractility in the antral circular muscle of guinea pig stomach. $Cd^{2+}$ inhibited the spontaneous contraction in a does dependent manner $(10^{-6}\;M\;10^{-4}\;M).\;Cd^{2+}\;(3{\times}10^{-5}M)$ suppressed 60 mM $K^+$ induced contracture composed or a phasic and a tonic response and the increased tonic response by the increased external $Ca^{2+}$ concentration. $Cd^{2+}$ also suppressed acetylcholine induced contracture composed of repetitive phasic and a tonic component and the increased tonic response by the increased external $Ca^{2+}$ concentration. Caffeine in the concentration of 1mM evoked contracture but $Cd^{2+}$ suppressed the contracture. $Cd^{2+}$ suppressed the amplitude of the $Na^+$ tee contracture dose dependently and the amplitude of $Na^+$ free contracture almost decreased to 20% of control amplitude in the concentration of $10^{-4}\;M\;Cd^{2+}$. From the above results, it is suggested that $Cd^{2+}$ may inhibit not only $Ca^{2+}$ influx via voltage sensitive, receptor operated $Ca^{2+}$ channel and Na/ca exchange but also intracellular $Ca^{2+}$ release from the sarcoplasmic reticulum in the antral circular muscle of guinea pig stomach.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.2
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• pp.215-223
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• 2018

Intracellular $Ca^{2+}$ mobilization is closely linked with the initiation of salivary secretion in parotid acinar cells. Reactive oxygen species (ROS) are known to be related to a variety of oxidative stress-induced cellular disorders and believed to be involved in salivary impairments. In this study, we investigated the underlying mechanism of hydrogen peroxide ($H_2O_2$) on cytosolic $Ca^{2+}$ accumulation in mouse parotid acinar cells. Intracellular $Ca^{2+}$ levels were slowly elevated when $1mM\;H_2O_2$ was perfused in the presence of normal extracellular $Ca^{2+}$. In a $Ca^{2+}-free$ medium, $1mM\;H_2O_2$ still enhanced the intracellular $Ca^{2+}$ level. $Ca^{2+}$ entry tested using manganese quenching technique was not affected by perfusion of $1mM\;H_2O_2$. On the other hand, $10mM\;H_2O_2$ induced more rapid $Ca^{2+}$ accumulation and facilitated $Ca^{2+}$ entry from extracellular fluid. $Ca^{2+}$ refill into intracellular $Ca^{2+}$ store and inositol 1,4,5-trisphosphate ($1{\mu}M$)-induced $Ca^{2+}$ release from $Ca^{2+}$ store was not affected by $1mM\;H_2O_2$ in permeabilized cells. $Ca^{2+}$ efflux through plasma membrane $Ca^{2+}-ATPase$ (PMCA) was markedly blocked by $1mM\;H_2O_2$ in thapsigargin-treated intact acinar cells. Antioxidants, either catalase or dithiothreitol, completely protected $H_2O_2-induced$ $Ca^{2+}$ accumulation through PMCA inactivation. From the above results, we suggest that excessive production of $H_2O_2$ under pathological conditions may lead to cytosolic $Ca^{2+}$ accumulation and that the primary mechanism of $H_2O_2-induced$ $Ca^{2+}$ accumulation is likely to inhibit $Ca^{2+}$ efflux through PMCA rather than mobilize $Ca^{2+}$ ions from extracellular medium or intracellular stores in mouse parotid acinar cells.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.2
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• pp.233-239
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• 2017

Intracellular calcium ($Ca^{2+}$) oscillation is an initial event in digestive enzyme secretion of pancreatic acinar cells. Reactive oxygen species are known to be associated with a variety of oxidative stress-induced cellular disorders including pancreatitis. In this study, we investigated the effect of hydrogen peroxide ($H_2O_2$) on intracellular $Ca^{2+}$ accumulation in mouse pancreatic acinar cells. Perfusion of $H_2O_2$ at $300{\mu}M$ resulted in additional elevation of intracellular $Ca^{2+}$ levels and termination of oscillatory $Ca^{2+}$ signals induced by carbamylcholine (CCh) in the presence of normal extracellular $Ca^{2+}$. Antioxidants, catalase or DTT, completely prevented $H_2O_2$-induced additional $Ca^{2+}$ increase and termination of $Ca^{2+}$ oscillation. In $Ca^{2+}$-free medium, $H_2O_2$ still enhanced CCh-induced intracellular $Ca^{2+}$ levels and thapsigargin (TG) mimicked $H_2O_2$-induced cytosolic $Ca^{2+}$ increase. Furthermore, $H_2O_2$-induced elevation of intracellular $Ca^{2+}$ levels was abolished under sarco/endoplasmic reticulum $Ca^{2+}$ ATPase-inactivated condition by TG pretreatment with CCh. $H_2O_2$ at $300{\mu}M$ failed to affect store-operated $Ca^{2+}$ entry or $Ca^{2+}$ extrusion through plasma membrane. Additionally, ruthenium red, a mitochondrial $Ca^{2+}$ uniporter blocker, failed to attenuate $H_2O_2$-induced intracellular $Ca^{2+}$ elevation. These results provide evidence that excessive generation of $H_2O_2$ in pathological conditions could accumulate intracellular $Ca^{2+}$ by attenuating refilling of internal $Ca^{2+}$ stores rather than by inhibiting $Ca^{2+}$ extrusion to extracellular fluid or enhancing $Ca^{2+}$ mobilization from extracellular medium in mouse pancreatic acinar cells.