• The Korean Journal of Physiology
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• v.27 no.2
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• pp.139-150
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• 1993

We have reported that dopamine potentiates spontaneous contractions dose-dependently in guinea-pig antral circular muscle strips (Hwang et al, 1991). To clarify the underlying excitatory mechanism of dopamine on the gastric smooth muscle, the effects of dopamine on voltage-dependent $Ca^{2+}\;currents\;and\;Ca^{2+}\;-dependent\;K^+\;currents$ were observed in enzymatically dispersed guinea-pig gastric myocytes using the whole-cell voltage-clamp technique. Experiments were also done using isometric tension recording and conventional intracellular microelectrode techniques. 1) The effect of dopamine on the spontaneous contraction of antral circular muscle strips of the guinea-pig was excitatory in a dose-dependent manner, and was blocked by phentolamine, an ${\alpha}-adrenoceptor$ blocker. 2) The slow waves were not changed by dopamine. 3) The voltage-operated inward $Ca^{2+}$ current was not influenced by dopamine. 4) The $Ca^{2+}\;-dependent\;K^+$ outward current, which might reflect the changes of intracellular calcium concentration, was enhanced by dopamine. This effect was abolished by phentolamine. 5) The enhancing effect of dopamine on the $Ca^{2+}\;-dependent\;K^+$ current disappeared with heparin which is known to block the action of $InsP_3$. From these results, it is suggested that dopamine acts via $InsP_3-mediated\;Ca^{2+}$ mobilization from intracellular stores and such action potentiates the spontaneous contraction of guinea-pig gastric smooth muscle.

• The Korean Journal of Zoology
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• v.34 no.2
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• pp.188-195
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• 1991

The effect of lanthanum ion (La3 +), which is associated with the mobilization of internal calcium, on the regulation of oocyte maturation was investigated with Rana dybowskii follicles. Follicular oocytes matured (germinal vesicle breakdown, GVBD) dose dependently when they were exposed to La3+ (O.O1-1.O mM) and the maturation occurred in 9-12 hours after the la3+(0.33 mM) stimulation. lanthanum also accelerated the onset of maturation of the lollicular oocytes exhibiting spontaneous maturation. Three hours of exposure to La3+ was enough to induce the maturation. The La3 + -induced maturation was not associated with progesterone production by follicle cells, and the maturation was inhibited by forskolin (9 $\mu$ M), and cyclobeximide (0.01 - 1.0 - $\mu$g/2 ml) in the medium. The La3+ and hormone stimulated maturation showed the same patterns of protein phosphorylation and dephosphorylation during the maturation. The data suggest that the oocyte maturation by La3+ stimulation is very similar to that by progesterone. Thus, it seems that internal mobilization of Ca2+ plays a key role in the initiation of oocyte maturation in amphibia.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.6
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• pp.717-730
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• 1997

$Mg^{2+}$ is the fourth most abundant cation in cellular organisms. Although the biological chemistry and the physiological roles of the magnesium ion were well known, the regulation of intracellular $Mg^{2+}$ in mammalian cells is not fully understood. More recently, however, the mechanism of $Mg^{2+}$ mobilization by hormonal stimulation has been investigated in hearts and in myocytes. In this work we have investigated the regulation mechanism responsible for the $Mg^{2+}$ mobilization induced by ${\alpha}1-adrenoceptor$ stimulation in perfused guinea pig hearts or isolated myocytes. The $Mg^{2+}$ content of the perfusate or the supernatant was measured by atomic absorbance spectrophotometry. The elimination of $Mg^{2+}$ in the medium increased the force of contraction of right ventricular papillary muscles. Phenylephrine also enhanced the force of contraction in the presence of $Mg^{2+}$-free medium. ${\alpha}1-Agonists$ such as phenylephrine were found to induce $Mg^{2+}$ efflux in both perfused hearts or myocytes. This was blocked by prazosin, a ${\alpha}1-adrenoceptor$ antagonist. $Mg^{2+}$ efflux by phenylephrine was amplified by $Na^+$ channel blockers, an increase in extracellular $Ca^{2+}$ or a decrease in extracellular $Na^+$. By contrast, the $Mg^{2+}$ influx was induced by verapamil, nifedipine, ryanodine, lidocaine or tetrodotoxin in perfused hearts, but not in myocytes. $W_7$, a $Ca^{2+}/calmodulin$ antagonist, completely blocked the pheylephrine-, A23187-, veratridine-, $Ca^{2+}-induced$ $Mg^{2+}$ efflux in perfused hearts or isolated myocytes. In addition, $Mg^{2+}$ efflux was induced by $W_7$ in myocytes but not in perfused heart. In conclusion, An increase in $Mg^{2+}$ efflux by ${\alpha}1-adrenoceptor$ stimulation in hearts can be through $IP_3$ and $Ca^{2+}-calmodulin$ dependent mechanism.

• Proceedings of the Korean Society of Food Hygiene and Safety Conference
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• 2004.05a
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• pp.230-230
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• 2004

• 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.

• Journal of Ginseng Research
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• v.47 no.1
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• pp.89-96
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• 2023

Background and aim: Panax ginseng, a key herbal medicine of replenishing Qi and tonifying Spleen, is widely used in the treatment of gastrointestinal diseases in East Asia. In this study, we aim to investigate the potential effects and mechanisms of polysaccharides from P. ginseng (PGP) on intestinal mucosal restitution which is one of the crucial repair modalities during the recovery of mucosal injury controlled by the Ca²⁺ signaling. Methods: Rat model of intestinal mucosal injury was induced by indomethacin. The fractional cell migration was carried out by immunohistochemistry staining with BrdU. The morphological observations on intestinal mucosal injury were also performed. Intestinal epithelial cell (IEC-6) migration in vitro was conducted by scratch method. Western-blot was adopted to determine the expressions of PLC-𝛾1, Rac1, TRPC1, RhoA and Cav-1. Immunoprecipitation was used to evaluate the levels of Rac1/PLC-𝛾1, RhoA/TRPC1 and Cav-1/TRPC1. Results: The results showed that PGP effectively reduced the assessment of intestinal mucosal injury, reversed the inhibition of epithelial cell migration induced by Indomethacin, and increased the level of Ca²⁺ in intestinal mucosa in vivo. Moreover, PGP dramatically promoted IEC-6 cell migration, the expression of Ca²⁺ regulators (PLC-𝛾1, Rac1, TRPC1, Cav-1 and RhoA) as well as protein complexes (Rac1/PLC-𝛾1, Cav-1/TRPC1 and RhoA/TRPC1) in vitro. Conclusion: PGP increases the Ca²⁺ content in intestinal mucosa partly through controlling the regulators of Ca²⁺ mobilization, subsequently promotes intestinal epithelial cell migration, and then prevents intestinal mucosal injury induced by indomethacin.

• Biomedical Science Letters
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• v.15 no.4
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• pp.319-326
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• 2009

Extracellular ATP elicits diverse physiological effects by binding to the G-protein-coupled P2Y receptors on the plasma membrane. In addition to the short-term effects of extracellular nucleotides on cell functions, there is evidence that such purinergic signalling can have long-term effects on cell proliferation, differentiation and death. The 3T3-L1 cell line derived from mouse embryo is a well-established and commonly utilized in vitro model for adipocytes differentiation and function. However, the distributions and roles of P2Y subtypes are still unknown in the preadipocyte. In this study, we identified the distributions and roles of P2Y subtypes in preadipocyte using $Ca^{2+}$ imaging and realtime PCR. ATP increased the $[Ca^{2+}]_i$ in a concentration-dependent manner. ATP increased $Ca^{2+}$ in absence and/or presence of extracellular $Ca^{2+}$. Suramin, non-selective P2Y blocker, largely blocked the ATP-induced $Ca^{2+}$ response. U73122, a PLC inhibitor, completely inhibited $Ca^{2+}$ mobilization in 3T3-L1 cells. The mRNA expression by realtime PCR of P2Y subtypes was $P2Y_2:P2Y_5:P2Y_6=1.0:12.5:0.3$. In conclusion, we showed that $P2Y_5$ receptor is a dominant purinergic receptor in preadipocytes, and multiple P2Y receptors could involve in differentiation and migration via regulating of intracellular calcium concentration.

• Biomedical Science Letters
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• v.25 no.4
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• pp.302-312
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• 2019

The aim of this work was to investigate the effect of black tea extract (BTE) on collagen -induced platelet aggregation. In this study, BTE (10~500 ㎍/mL) was shown to inhibit platelet aggregation via thromboxane A₂ (TXA₂) down-regulation by blocking cyclooxygenase-1 (COX-1) activity. Also, BTE decreased intracellular Ca²⁺ mobilization ([Ca²⁺]_i). Additionally, BTE enhanced the levels of both cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which are aggregation-inhibiting molecules. BTE inhibited the phosphorylation of phospholipase C (PLC) γ2 and syk activated by collagen. BTE regulated platelet aggregation via cAMP-dependent phosphorylation of vasodilator-stimulated phosphoprotein (VASP) Ser¹⁵⁷. The anti-platelet effects of BTE in high fat diet (HFD)-induced obese rats were evaluated. After eight weeks of BTE treatment (300 and 600 mg/kg), the platelet aggregation rate in the treated groups was significantly less than that in the HFD-fed control group. Also, BTE exhibited a hepatoprotective effect and did not exert hepatotoxicity. Therefore, these data suggest that BTE has anti-platelet effects on collagen-stimulated platelet aggregation and may have therapeutic potential for the prevention of platelet-mediated thrombotic diseases.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.1
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• pp.27-32
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• 2009

The effects of oxidized low-density lipoprotein(OxLDL) and its major lipid constituent lysophosphatidylcholine(LPC) on $Ca^{2+}$ entry were investigated in cultured human umbilical endothelial cells(HUVECs) using fura-2 fluorescence and patch-clamp methods. OxLDL or LPC increased intracellular $Ca^{2+}$ concentration($[Ca^{2+}]_i$), and the increase of $[Ca^{2+}]_i$ by OxLDL or by LPC was inhibited by $La^{3+}$ or heparin. LPC failed to increase $[Ca^{2+}]_i$ in the presence of an antioxidant tempol. In addition, store-operated $Ca^{2+}$ entry(SOC), which was evoked by intracellular $Ca^{2+}$ store depletion in $Ca^{2+}$-free solution using the sarcoplasmic reticulum $Ca^{2+}$ pump blocker, 2, 5-di-t-butyl-l,4-benzohydroquinone(BHQ), was further enhanced by OxLDL or by LPC. Increased SOC by OxLDL or by LPC was inhibited by U73122. In voltage-clamped cells, OxLDL or LPC increased $[Ca^{2+}]_i$ and simultaneously activated non-selective cation(NSC) currents. LPC-induced NSC currents were inhibited by 2-APB, $La^{3+}$ or U73122, and NSC currents were not activated by LPC in the presence of tempol. Furthermore, in voltage-clamped HUVECs, OxLDL enhanced SOC and evoked outward currents simultaneously. Clamping intracellular $Ca^{2+}$ to 1 ${\mu}M$ activated large-conductance $Ca^{2+}$-activated $K^+(BK_{ca})$ current spontaneously, and this activated $BK_{ca}$ current was further enhanced by OxLDL or by LPC. From these results, we concluded that OxLDL or its main component LPC activates $Ca^{2+}$-permeable $Ca^{2+}$-activated NSC current and $BK_{ca}$ current simultaneously, thereby increasing SOC.

• Development and Reproduction
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• v.5 no.1
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• pp.53-57
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• 2001

Sperm capacitation and acrosome reaction (AR) have been known to be Ca$^{2+}$-dependent events. Sperm capacitation accompanies with cholesterol efflux fiom plasma membrane, that eventually stimulates AR. However, whether the AR mediated by cholesterol efflux is Ca$^{2+}$ dependent has not been verified yet. Recently, methyl beta cyclodextrin (MBCD) was found to evoke AR by stimulating the cholesterol efflux fiom sperm membrane. In the present study, we examined the requirement of Ca$^{2+}$ in the MBCD-induced AR. During incubation of sperm in the bicarbonate buffered media MBCD increased AR in a dose-dependent manner regardless of the Ca$^{2+}$ presence. In the presence of low molar concentration of Ca$^{2+}$ (100 ${\mu}$M), MBCD-induced AR was slightly increased compared to Ca$^{2+}$-free condition. In the absence of Ca$^{2+}$ supplement, spontaneous AR was slightly increased during the incubation but inhibited by 100 ${\mu}$M EGTA. MBCD potentiated AR even the presence of EGTA. However, EGTA attenuated MBCD-induced AR, suagesting the functional involvement of intracellular Ca$^{2+}$ in the MBCD-induced AR. Taken together, it was suggested that cholesterol efflux from the sperm plasma membrane was sufficient for induction of AR even in the absence of extracellular Ca$^{2+}$and that a condition permissive for mobilization of intracellular Ca$^{2+}$ is important for MBCD-induced AR.