• The Korean Journal of Physiology and Pharmacology
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• v.2 no.1
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• pp.41-48
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• 1998

The present study was undertaken to characterize homocysteic acid (HCA)-and cysteic acid (CA)-mediated formation of inositol phosphates (InsP) in primary culture of rat cerebellar granule cells. HCA and CA stimulated InsP formation in a dose-dependent manner, which was prevented by the N-methyl-D-aspartate (NMDA) receptor antagonist D,L-2-amino-5-phosphopentanoic acid (APV). CA-, but not HCA-, mediated InsP formation was in part prevented by the metabotropic glutamate receptor antagonist ?${\alpha}$-methyl-4-carboxyphenylglycine ($({\pm})$-MCPG). Both HCA- and CA-mediated increases in intracellular calcium concentration were completely blocked by APV, but were not altered by $({\pm})$-MCPG. CA-mediated InsP formation was in part prevented by removal of endogenous glutamate. In contrast, the glutamate transport blocker L-aspartic acid-${\beta}$-hydroxamate synergistically increased CA responses. These data indicate that in cerebellar granule cells HCA mediates InsP formation wholly by activating NMDA receptor. In contrast, CA stimulates InsP formation by activating both NMDA receptor and metabotropic glutamate receptor, and in part by releasing endogenous glutamate into extracellular milieu.

• Microbiology and Biotechnology Letters
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• v.25 no.6
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• pp.592-597
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• 1997

During the screening of inhibitors against phospholipase C (PLC) and the formation of inositol phosphates (IP$_{t}$) at NIH3T3${\gamma}$1 cells from microbial secondary metabolites, we selected a fungal strain MT60109 which was capable of producing an inhibitor. By the taxonomic studies, this fungus was identified as Pseudallescheria sp. MT60109 and an inhibitor of PLC was purified by BuOH extraction and chromatographic techniques from the culture broth of Pseudallescheria sp. MT60109. The inhibitor was identified as thielavin B by the physico-chemical properties and spectroscopic analysis of UV, FAB-MS, $^{1}$H, $^{13}$C-NMR, $^{1}$H-$^{1}$H COSY and HMBC. Thielavin B showed potent inhibitory activity against PLC purified from bovine brain with an IC$_{50}$ of 20 $\mu$M. And it also inhibited the formation of inositol phosphates in platelet-derived growth factor (PDGF) -stimulated NIH3T3${\gamma}$1 cells with an IC$_{50}$ of 20 $\mu$M.

• YAKHAK HOEJI
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• v.41 no.4
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• pp.433-438
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• 1997

MT 51005 as a potent inhibitor of phospholipase C(PLC) was purified from the culture broth of a fungal strain No. 51005 isolated from soil. It was identified as a benzaldehyde d erivative, anguillosporal. by the physico-chemical properties and spectroscopic data. Anguillosporal showed the inhibitory activity against purified PLC with an $IC_{50}\;of\;13{\mu}g/ml$. And it also inhibited the formation of inositol phosphates($IP_t$) in platelet-derived growth factor(PDGF)-stimulated $NIH3T3{\gamma}1$ cells with an $IC_{50}\;of\;0.8{\mu}g/ml$.

• YAKHAK HOEJI
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• v.44 no.2
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• pp.162-168
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• 2000

To investigate the effects of protein kinases on endothelin-1-induced phospholipase C activation and $Ca^{2+}$ mobilization in Rat-2 fibroblast, we measured the formation of inositol phosphates and intracellular $Ca^{2+}$ concentration with [$^3$H]inositol and Fura-2/AM, respectively. Endothelin-1 dose-dependently activated phospholipase C and increased intracellular $Ca^{2+}$ concentration. Protein kinase C activator PMA, significantly inhibited both phospholipase C activity and $Ca^{2+}$ mobilization induced by endothelin-1. Tyrosine kinase inhibitor, genistein, inhibited both. On the other hand, cyclic nucleotide (cAMP and cGMP) did not have any influence on the signaling pathway of phospholipase C-Ca$^{2+}$ mobilization induced by endothelin-1. These results suggest that protein kinase C and tyrosine kinase counteract on the signaling pathway of phospholipase C-Ca$^{2+}$ mobilization induced by endothelin-1 in Rat-2 fibroblast. fibroblast.

• The Korean Journal of Physiology and Pharmacology
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• v.8 no.1
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• pp.57-63
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• 2004

Fluoxetine, a widely used anti-depressant compound, has several additional effects, including blockade of voltage-gated ion channels. We examined whether fluoxetine affects ATP-induced calcium signaling in PC12 cells by using fura-2-based digital calcium imaging and assay for $[^3H]-inositol$ phosphates (IPs). Treatment with ATP $(100\;{\mu}M)$ for 2 min induced $[Ca^{2+}]_i$ increases. The ATP-induced $[Ca^{2+}]_i$ increases were significantly decreased by removal of extracellular $Ca^{2+}$ and treatment with the inhibitor of endoplasmic reticulum $Ca^{2+}$ ATPase thapsigargin $(1\;{\mu}M)$. Treatment with fluoxetine for 5 min blocked the ATP-induced $[Ca^{2+}]_i$ increase concentration-dependently. Treatment with fluoxetine $(30\;{\mu}M)$ for 5 min blocked the ATP-induced $[Ca^{2+}]_i$ increase following removal of extracellular $Ca^{2+}$ and depletion of intracellular $Ca^{2+}$ stores. While treatment with the L-type $Ca^{2+}$ channel antagonist nimodipine for 10 min inhibited the ATP-induced $[Ca^{2+}]_i$ increases significantly, treatment with fluoxetine alone blocked the ATP-induced responses. Treatment with fluoxetine also inhibited the 50 mM $K^+-induced$ $[Ca^{2+}]_i$ increases completely. However, treatment with fluoxetine did not inhibit the ATP-induced $[^3H]-IPs$ formation. Collectively, we conclude that fluoxetine inhibits ATP-indueed $[Ca^{2+}]_i$ increases in PC12 cells by inhibiting both an influx of extracellular $Ca^{2+}$ and a release of $Ca^{2+}$ from intracellular stores without affecting IPs formation.