• 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 ${\beta}-cells$.

• Development and Reproduction
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• v.7 no.2
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• pp.81-88
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• 2003

Initiation and activation of sperm motility are prerequisite processes for the contact and fusion of male and female gametes at fertilization. The phenomena are under the regulation of CAMP and $Ca^{2+}$ in vertebrates and invertebrates. Mammalian sperm requires $Ca^{2+}$and cyclic AMP for the activation of sperm motility. Cell signaling for the initiation and activation of sperm motility has been well studied in the ascidians, Ciona intestinalis and C. savignyi and salmonid fishes. In Ciona, whose cell signaling for activation of sperm motility has been established, the sperm-activating and -attracting factor released from unfertilized egg requires extracellular $Ca^{2+}$ for activating sperm motility and eliciting chemotactic behavior of the activated sperm toward the egg. On the other hand, the cyclic AMP-dependent phosphorylation of protein is essential for the initiation of sperm motility in salmonid fishes. A decrease in the environmental Ti concentration surrounding the spawned sperm causes a li efflux and $Ca^{2+}$ influx through the specific $K^{+}$ channel and dihydropyridine-sensitive L-/T- type $Ca^{2+}$ channel, respectively, thereby leading to the membrane hyperpolarization and $Ca^{2+}$ influx. The membrane hyperpolarization synthesizes cyclic AMP, which triggers the luther Process of cell signaling, i.e., cyclic AMP-dependent protein phosphorylation, to initiate sperm motility in salmond fishes.almond fishes.

• Archives of Pharmacal Research
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• v.28 no.4
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• pp.413-420
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• 2005

We previously demonstrated the ability of ginseng saponins (active ingredients of Panax ginseng) to enhance $Ca^{2+}$-activated $Cl^{-}$ current. The mechanism for this ginseng saponin-induced enhancement was proposed to be the release of $Ca^{2+}$ from $IP_{3}-sensitive$ intracellular stores through the activation of PTX-insensitive $G\alpha_{q/11}$ proteins and PLC pathway. Recent studies have shown that calmodulin (CaM) regulates $IP_{3}$ receptor-mediated $Ca^{2+}$ release in both $Ca^{2+}-dependent$ and -independent manner. In the present study, we have investigated the effects of CaM on ginseng saponin-induced $Ca^{2+}$-activated $Cl^{-}$ current responses in Xenopus oocytes. Intraoocyte injection of CaM inhibited ginseng saponin-induced $Ca^{2+}$-activated $Cl^{-}$ current enhancement, whereas co-injection of calmidazolium, a CaM antagonist, with CaM blocked CaM action. The inhibitory effect of CaM on ginseng saponin-induced $Ca^{2+}$-activated $Cl^{-}$ current enhancement was dose- and time-dependent, with an $IC_{50} of 14.9\pm3.5 {\mu}M$. The inhibitory effect of CaM on saponin's activity was maximal after 6 h of intraoocyte injection of CaM, and after 48 h the activity of saponin recovered to control level. The half-recovery time was calculated to be $16.7\pm4.3 h$. Intraoocyte injection of CaM inhibited $Ca^{2+}$-induced $Ca^{2+}$-activated $Cl^{-}$ current enhancement and also attenuated $IP_{3}$-induced $Ca^{2+}$-activated $Cl^{-}$ current enhancement. $Ca^{2+}$/CaM kinase II inhibitor did not inhibit CaM-caused attenuation of ginseng saponin-induced $Ca^{2+}$-activated $Cl^{-}$ current enhancement. These results suggest that CaM regulates ginseng saponin effect on $Ca^{2+}$-activated $Cl^{-}$ current enhancement via $Ca^{2+}$-independent manner.

• 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.

• The Korean Journal of Physiology
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• v.23 no.2
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• pp.329-337
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• 1989

Cardiac muscles show stimulation frequency-dependent tension changes i.e. Bowditch phenomenon and Woodworth phenomenon, the former is an increase of tension with the increase of stimulation frequency, whereas the latter is an increase of tension with a decrease of stimulation frequency. Bowditch phenomenon is seen in the range of frequency 1.0 cps and above, and Woodworth phenomenon below the frequency 1.0 cps in the most of mammalian cardiac atrium. To throw some light on the possible mechanism of both phenomena in rat atrium, influences of drugs affecting $Ca^{2+}$ influx through the plasma membrane $(verapamil,\;La^{3+},\;norepinephrine)$ and $Ca^{2+}$ release from sarcoplasmic reticulum (SR) on frequency-tension curve were studied. The results obtained are summarized as follows: 1) At low temperature $(27.5^{\circ}C)$, both Bowditch and Woodworth phenomenon were demonstrated. But Bowditch phenomenon disappeared at the temperature above $(32.5^{\circ}C)$. 2) At $(27.5^{\circ}C)$, in the presence of verapamil, a $Ca^{2+}$ channel blocker, a time course of change in the frequency-tension was studied. It was found that Bowditch phenomenon was affected before the Woodworth phenomenon, then the former was completely disappeared. At $(32.5^{\circ}C)$, where no Bow-ditch is seen in normal atrial muscle, Bowditch phenomenon was reappeared by an administration of norepinephrine suggesting again that slow inward current of such as $Ca^{2+}$ channel is closely related to Bowditch phenomenon. 3) At $27.5^{\circ}C$, in the presence of $La^{3+}$, although tensions were decreased at all stimulation frequencies, Bowditch and Woodworth phenomenon were still demonstrated. However in the presence of both $La^{3+}$ and verapamil, Bowditch phenomena was disappeared suggesting that $La^{3+}$ is less effective in blocking $Ca^{2+}$ channel than verapamil. 4) At $27.5^{\circ}C$, in the presence of ryanodine, an inhibitor of calcium release from SR, Woodworth phenomenon was disappeared, which was consistent with previous reports of others, suggesting that $Ca^{2+}$ release from SR is closely related to Woodworth phenomenon. From the above findings, it may be concluded that Bowditch phenomenon is dependent on the magnitude of $Ca^{2+}$ influx through slow channel and Woodworth phenomenon is dependent on the amount of $Ca^{2+}$ stored in SR.

• Archives of Pharmacal Research
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• v.18 no.3
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• pp.153-158
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• 1995

The levels of extracellualr glutamate, intracellular $Ca^{2+}\;([Ca2+]_i)$ and cGMP were determined for 1 h with the excitatory amino acids, N-methyl-D-aspartate (NMDA) or kainate in cultured cerebellar granule cells. Both NMDA and kainate produced a time-dependent release of glutamate, and kainate was more potent than NMDA in glutamate elevation. The elevation of extracellular glutamate was not purely governed by intracellular $Ca^{2+}$ concentration. However, in opposite to the time-dependent elevation of glutamate, the elevation of cGMP by NMDA and kainate were at maximum level in short-time (1 min) incubation then remarkably decreased with longer incubation times. Post-applications (30 min after agonist) of EAA antagonist did not block EAAs-induced glutamate elevation. However, NMDA antagonist, phencyclidine (PCP), blocked NMDA-induced cGMP elevation at pre- or post-application, but kainate antagonist, 6,7-dinitroquinoxaline-2,3-dione (DNQX), paradoxically augmented kainate-induced cGMP elevation for 1 h incubation. These results show that NMDA or kainate induces time-dependent elevations of extracellular glutamate, while the elevations of cGMP by these EAAs are remarkably decreased with longer incubation times. However, NMDA- arid kainate-indcued glutamate release was blocked by pre-application of each receptor antagonist but not by post-application while EAA-induced $[Ca^{2+}]_i$ was blocked by post-application of antagonist. These observations suggest that EAA-induced elevation of $[Ca^{2+}]_i$ is not parallel with elevation of glutamate release or cGMP.

• Proceedings of the Zoological Society Korea Conference
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• 2000.10a
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• pp.190.2-190
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• 2000

No Abstract, See Full Text

• Natural Product Sciences
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• v.10 no.3
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• pp.114-118
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• 2004

It is reported that $(1R,9S)-{\beta}-Hydrastine$ hydrochloride (BHSH) decreased the intracellular dopamine content by inhibiting tyrosine hydroxylase (TH) activity in PC12 cells. In this study, the inhibitory mechanisms on TH activity by BHSH in PC12 cells were investigated. BHSH treatment caused a reduction of TH activity and TH mRNA level in a dose-dependent manner. After the treatment of $20\;{\mu}M$ BHSH, TH activity and TH mRNA content were reduced at 15 min, reached the minimal levels at 6-24 h, and then recovered gradually to the control level. BHSH at $10-50\;{\mu}M$ caused a decrease in the basal intracellular cyclic AMP levels at 10 min in a concentration-dependent manner. In addition, BHSH at $20-100\;{\mu}M$ decreased the basal intracellular $Ca^{2+}$ concentration $([Ca^{2+}]_i)$ immediately in a dose-dependent manner. BHSH also inhibited the 56 mM $K^+ $ depolarization-induced elevation in $[Ca^{2+}]_i$, and blocked caffeine-activated store-operated $Ca^{2+}$ entry in PC12 cells. These data suggest that BHSH inhibits TH activity and TH gene expression, in part, through reducing cyclic AMP content and basal $[Ca^{2+}]_i$ in PC12 cells.

• Animal cells and systems
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• v.16 no.4
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• pp.269-273
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• 2012

Controlling metabolism throughout life is a necessity for living creatures, and perturbation of energy balance elicits disorders such as type-2 diabetes mellitus and cardiovascular disease. $Ca^{2+}$ plays a key role in regulating energy generation. $Ca^{2+}$ homeostasis of the endoplasmic reticulum (ER) lumen is maintained through the action of $Ca^{2+}$ channels and the $Ca^{2+}$ ATPase pump. Once released from the ER, $Ca^{2+}$ is taken up by mitochondria where it facilitates energy metabolism. Mitochondrial $Ca^{2+}$ serves as a key metabolic regulator and determinant of cell fate, necrosis, and/or apoptosis. Here, we focus on $Ca^{2+}$ transport from the ER to mitochondria, and $Ca^{2+}$-dependent regulation of mitochondrial energy metabolism.

• Biomolecules & Therapeutics
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• v.22 no.3
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• pp.223-231
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• 2014

In this study, we prepared cordycepin-enriched (CE)-WIB801C, a n-butanol extract of Cordyceps militaris-hypha, and investigated the effect of CE-WIB801C on collagen-induced human platelet aggregation. CE-WIB801C dose-dependently inhibited collagen-induced platelet aggregation, and its $IC_{50}$ value was $175{\mu}g/ml$. CE-WIB801C increased cAMP level more than cGMP level, but inhibited collagen-elevated $[CA^{2+}]_i$ mobilization and thromboxane $A_2$ ($TXA_2$) production. cAMP-dependent protein kinase (A-kinase) inhibitor Rp-8-Br-cAMPS increased the CE-WIB801C-downregulated $[CA^{2+}]_i$ level in a dose dependent manner, and strongly inhibited CE-WIB801C-induced inositol 1, 4, 5-trisphosphate receptor ($IP_3R$) phosphorylation. These results suggest that the inhibition of $[CA^{2+}]_i$ mobilization by CE-WIB801C is resulted from the cAMP/A-kinase-dependent phosphorylation of $IP_3R$. CE-WIB801C suppressed $TXA_2$ production, but did not inhibit the activities of cyclooxygenase-1 (COX-1) and $TXA_2$ synthase (TXAS). These results suggest that the inhibition of $TXA_2$ production by WIB801C is not resulted from the direct inhibition of COX-1 and TXAS. In this study, we demonstrate that CE-WIB801C with cAMP-dependent $CA^{2+}$-antagonistic antiplatelet effects may have preventive or therapeutic potential for platelet aggregation-mediated diseases, such as thrombosis, myocardial infarction, atherosclerosis, and ischemic cerebrovascular disease.