• The Korean Journal of Physiology
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• 제29권1호
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• pp.13-27
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• 1995

single $K^{+}$ channels of skeletal muscle from the rat and frog were into planar lipid bilayers and their properties were studied. Fusion was induced by an osmotic gradient. Of the four types of $K^{+}$ channels recorded, the two most frequently observed were a voltage and $Ca^{2+}-activated$ $K^{+}$ channel and a $K^{+}$ channel with a prominent conductance substate. The first $K^{+}$ channel was identified as the large $Ca^{2+}-activated$ $K^{+}$ (BK) channel because the open-state probability was increased with depolarization (e-fold change per $10.6{\pm}3.5$ mV, n=8) and internal $Ca^{2+}$ (half-activation at $16.7{\pm}3.8$ mV, n=8, pCa 4) and its conductance was large ($247{\pm}4.9$ pS, n=24 in 0.1 M KCI). Lifetime distributions of open- and closed-states could be fitted with single exponentials of several milliseconds. The mean open- and closed-lifetimes were linearly dependent on the intracellular $[Ca^{2+}]$ and $1/[Ca^{2+}]$, respectively. The second $K^{+}$ channel showed a conductance substate at $30{\sim}60%$ of the open state. Its current-voltage relation was linear in the range of $-80\;{\sim}\;+80\;mV$. The slope conductance of the substate and open-state were 40 and 144 pS in 0.2 M KCl, respectively. The channel was highly selective for $K^{+}$ over Cl. The open-state probability was weakly voltage-dependent (e-fold change per 35 mV. The lifetime distributions of open- and closed-states were fitted with two exponentials and the major gating occurred slowly at several hundred milliseconds. Based on the above results, we think the second type of $K^{+}$ channel is the sarcoplasmic reticulum $K^{+}$ (SRK) channel. In addition, both types of channel were also incorporated into the lipids extracted from the skeletal muscle. The channel properties recorded in the bilayers termed from synthetic and extracted lipids were qualitatively similar. Our data indicate that BK and SRK channels are rich in the skeletal muscle and their properties and regulation could be effectively studied in planar lipid bilayer.

• The Korean Journal of Physiology and Pharmacology
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• 제12권2호
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• pp.59-64
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• 2008

In our previous study, we found that spermine and putrescine inhibited spontaneous and acetylcholine (ACh)-induced contractions of guinea-pig stomach via inhibition of L-type voltage- dependent calcium current ($VDCC_L$). In this study, we also studied the effect of spermidine on mechanical contractions and calcium channel current ($I_{Ba}$), and then compared its effects to those by spermine and putrescine. Spermidine inhibited spontaneous contraction of the gastric smooth muscle in a concentration-dependent manner ($IC_{50}=1.1{\pm}0.11mM$). Relationship between inhibition of contraction and calcium current by spermidine was studied using 50 mM high $K^+$-induced contraction: Spermidine (5 mM) significantly reduced high $K^+$ (50 mM)-induced contraction to 37${\pm}$4.7% of the control (p<0.05), and inhibitory effect of spermidine on $I_{Ba}$ was also observed at a wide range of test potential in current/voltage (I/V) relationship. Pre- and post-application of spermidine (5 mM) also significantly inhibited carbachol (CCh) and ACh-induced initial and phasic contractions. Finally, caffeine (10 mM)-induced contraction which is activated by $Ca^{2+}$-induced $Ca^{2+}$ release (CICR), was also inhibited by pretreatment of spermidine (5 mM). These findings suggest that spermidine inhibits spontaneous and CCh-induced contraction via inhibition of $VDCC_L$ and $Ca^{2+}$ releasing mechanism in guinea-pig stomach.

• Journal of Ginseng Research
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• 제39권2호
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• pp.169-177
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• 2015

Background: Ginsenoside Rd (GSRd), one of the most abundant ingredients of Panax ginseng, protects the heart via multiple mechanisms including the inhibition of $Ca^{2+}$ influx.We intended to explore the effects of GSRd on L-type $Ca^{2+}$ current ($I_{Ca,L}$) and define the mechanism of the suppression of $I_{Ca,L}$ by GSRd. Methods: Perforated-patch recording and whole-cell voltage clamp techniques were applied in isolated rat ventricular myocytes. Results: (1) GSRd reduced $I_{Ca,L}$ peak amplitude in a concentration-dependent manner [half-maximal inhibitory concentration $(IC_{50})=32.4{\pm}7.1{\mu}mol/L$] and up-shifted the current-voltage (I-V) curve. (2) GSRd ($30{\mu}mol/L$) significantly changed the steady-state activation curve of $I_{Ca,L}$ ($V_{0.5}:-19.12{\pm}0.68$ vs. $-6.26{\pm}0.38mV$; n = 5, p < 0.05) and slowed down the recovery of $I_{Ca,L}$ from inactivation [the time content (${\zeta}$) from 91 ms to 136 ms, n = 5, p < 0.01]. (3) A more significant inhibitive effect of GSRd ($100{\mu}mol/L$) was identified in perforated-patch recording when compared with whole-cell recording [$65.7{\pm}3.2%$ (n = 10) vs. $31.4{\pm}5.2%$ (n = 5), p < 0.01]. (4) Pertussis toxin ($G_i$ protein inhibitor) completely abolished the $I_{Ca,L}$ inhibition induced by GSRd. There was a significant difference in inhibition potency between the two cyclic adenosine monophosphate elevating agents (isoprenaline and forskolin) prestimulation [$55{\pm}7.8%$ (n = 5) vs. $17.2{\pm}3.5%$ (n = 5), p < 0.01]. (5) 1H-[1,2,4]Oxadiazolo[4,3-a]-quinoxalin-1-one (a guanylate cyclase inhibitor) and N-acetyl-$\small{L}$-cysteine (a nitric oxide scavenger) partly recovered the $I_{Ca,L}$ inhibition induced by GSRd. (6) Phorbol-12-myristate-13-acetate (a protein kinase C activator) and GF109203X (a protein kinase C inhibitor) did not contribute to the inhibition of GSRd. Conclusion: These findings suggest that GSRd could inhibit $I_{Ca,L}$ through pertussis toxin-sensitive G protein ($G_i$) and a nitric oxide-cyclic guanosine monophosphate-dependent mechanism.

• Archives of Pharmacal Research
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• 제28권6호
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• pp.709-715
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• 2005

The purpose of this study was to investigate the effect of atropine on peripheral vasodilation and the mechanisms involved. The isometric tension of rat mesenteric artery rings was recorded in vitro on a myograph. The results showed that atropine, at concentrations greater than 1$\mu$M, relaxed the noradrenalin (NA)-precontracted rat mesenteric artery in a concentration-dependent manner. Atropine-induced vasodilatation was mediated, in part, by an endothelium-dependent mechanism, to which endothelium-derived hyperpolarizing factor may contribute. Atropine was able to shift the NA-induced concentration-response curve to the right, in a non-parallel manner, suggesting the mechanism of atropine was not mediated via the ${\alpha}_1$-adrenoreceptor. The $\beta$-adrenoreceptor and ATP sensitive potassium channel, a voltage dependent calcium channel, were not involved in the vasodilatation. However, atropine inhibited the contraction derived from NA and $CaCl_2$ in $Ca^{2+}$-free medium, in a concentration dependent manner, indicating the vasodilatation was related to the inhibition of extracellular $Ca^{2+}$ influx through the receptor-operated calcium channels and intracellular $Ca^{2+}$ release from the $Ca^{2+}$ store. Atropine had no effect on the caffeine-induced contraction in the artery segments, indicating the inhibition of intracellular $Ca^{2+}$ release as a result of atropine most likely occurs via the IP3 pathway rather than the ryanodine receptors. Our results suggest that atropine-induced vasodilatation is mainly from artery smooth muscle cells due to inhibition of the receptor-mediated $Ca^{2+}$-influx and $Ca^{2+}$-release, and partly from the endothelium mediated by EDHF.

• 식품기술
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• 제18권2호
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• pp.52-58
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• 2005

최근 20여년 동안 Panax ginseng의 다양한 효과가 연구 되어져 왔다. Panax ginseng의 주요 활성 성분인 ginsenosides는 오직 인삼에서만 발견되어지는 saponin이다. 최근 들어 신경, 非신경 또는 복합적으로 분포된 세포에서 ginsenoside가 $Ca^2+$, $K^+$,$Na^+$,$Cl^-$ channel이나 ligand gated ionchannel (5-HT3, nicotinic acetylcholine, NMDA receptor)과 같은 다양한 ion channel을 조절하는증거들이 발표되고 있다. Ginsenoside는 voltage-dependent $Ca^2+$, $K^+$,$Na^+$ channel의 활성을 억제하는 반면 $Ca^2+$-activated $Cl^-$ channel이나 $Ca^2+$-activated $K^+$ channel의 활성은 증가 시키는 것으로 나타났다. 또한 흥분성 ligand-gated ion channel인 $5-HT_3$, nicotinic acetylcholine, NMDA receptor의 활성은 억제한다. 본 총설에서는 현재까지 알려진 ion channel 활성에 대한 ginsenoside의 조절작용과 이것으로 인해 어떻게 생물학적 효능과 연결이 되어있는지에 대하여 이야기하고자 한다.

• Biomolecules & Therapeutics
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• 제17권1호
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• pp.32-42
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• 2009

The purpose of the present study was to examine the effect of dihydrexidine, a full $D_1$ receptor agonist, on the secretion of catecholamines (CA) from the perfused model of the rat adrenal gland, and to establish its mechanism of action. Dihydrexidine (10-100 ${\mu}M$), perfused into an adrenal vein for 60 min, relatively produced dose- and time-dependent inhibition in the CA secretory responses evoked by ACh (5.32 mM), high $K^+$ (56 mM), DMPP (100 ${\mu}M$) and McN-A-343 (100 ${\mu}M$). Dihydrexidine itself did fail to affect basal CA output. Also, in adrenal glands loaded with dihydrexidine (30 ${\mu}M$), the CA secretory responses evoked by Bay-K-8644 (10 ${\mu}M$), an activator of L-type $Ca^{2+}$ channels, cyclopiazonic acid (10 ${\mu}M$), an inhibitor of cytoplasmic $Ca^{2+}$-ATPase, and veratridine, an activator of voltage-dependent $Na+$ channels (10 ${\mu}M$), were also markedly inhibited, respectively. However, in the simultaneous presence of dihydrexidine (30 ${\mu}M$) and R (+)-SCH23390 (a selective antagonist of $D_1$ receptor, 3 ${\mu}M$), the CA secretory responses evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644, cyclopiazonic acid and veratridine were considerably recovered to the extent of the corresponding control secretion compared with the inhibitory responses by dihydrexidinetreatment alone. In conclusion, these experimental results suggest that dihydrexidine significantly inhibits the CA secretion evoked by cholinergic stimulation (both nicotinic and muscarinic receptors) and membrane depolarization from the rat adrenal medulla. It seems that this inhibitory effect of dihydrexidine may be mediated by inhibiting influx of both $Ca^{2+}$ and $Na^+$ into the cytoplasm as well as by suppression of $Ca^{2+}$ release from cytoplasmic calcium store through activation of dopaminergic $D_1$ receptors located on the rat adrenomedullary chromaffin cells.

• 약학회지
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• 제41권5호
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• pp.666-671
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• 1997

We studied effects of genistein and tyrphostin, inhibitors of tyrosine kinase, on contractions induced by high $K^+$ and norepinephrine in rat aorta. Genistein $(10^{-6}{\sim}10^{-4}M)$ and tyrphostin ($(10^{-5}{\sim}10^{-4}M)$) inhibited high $K^+$ and norepinephrine-induced sustained contractions, respectively in a concentration-dependent manner. High $K^+$ and norepinephrine caused an increase in $^{45}Ca^{2+}$ uptake while $10^{-4}M$ genistein and tyrphostin inhibited the $K^+$ and norepinephrine-increased $^{45}Ca^{2+}$ uptake, respectively. These results show that inhibitor of tyrosine kinase blocks the voltage-and receptor-operated $Ca^{2+}$ channels in rat aorta, respectively.

• 고려인삼학회:학술대회논문집
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• 고려인삼학회 2005년도 창립30주년기념 추계 학술대회 및 정기총회
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• pp.32-40
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• 2005

The last two decades have shown a marked expansion in publications of diverse effects of Panax ginseng. Ginsenosides, as active ingredients of Panax ginseng, are saponins found in only ginseng. Recently, a line of evidences shows that ginsenosides regulate various types of ion channel activity such as Ca$^{2+}$, K$^+$, Na$^+$, Cl$^-$, or ligand gated ion channels (i.e. 5-HT$_3$, nicotinic acetylcholine, or NMDA receptor) in neuronal, non-neuronal cells, and heterologously expressed cells. Ginsenosides inhibit voltage-dependent Ca$^{2+}$, K$^+$, and Na$^+$ channels, whereas ginsenosides activate Ca$^{2+}$-activated Cl$^-$ and Ca$^{2+}$-activated K$^+$ channels. Ginsenosides also inhibit excitatory ligand-gated ion channels such as 5-HT$_3$. nicotinic acetylcholine, and NMDA receptors. This presentation will introduce recent findings on the ginsenoside-induced differential regulations of ion channel activities as a ligand as other drugs do.

• The Korean Journal of Physiology and Pharmacology
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• 제18권5호
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• pp.377-381
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• 2014

Propofol is a widely used anesthetic. Many studies have shown that propofol has direct effects on blood vessels, but the precise mechanism is not fully understood. Secondary intrapulmonary artery rings from male rats were prepared and mounted in a Multi Myograph System. The following constrictors were used to induce contractions in isolated artery rings: high $K^+$ solution (60 mmol/L); U46619 solution (100 nmol/L); 5-hydroxytryptamine (5-HT; $3{\mu}mol/L$); or phenylephrine (Phe; $1{\mu}mol/L$). The relaxation effects of propofol were tested on high $K^+$ or U46619 precontracted rings. Propofol also was added to induce relaxation of rings preconstricted by U46619 after pretreatment with the nitric oxide synthase inhibitor $N^G$-nitro-L-arginine methyl ester (L-NAME). The effects of propofol on $Ca^{2+}$ influx via the L-type $Ca^{2+}$ channels were evaluated by examining contraction-dependent responses to $CaCl_2$ in the absence or presence of propofol (10 to $300{\mu}mol/L$). High $K^+$ solution and U46619 induced remarkable contractions of the rings, whereas contractions induced by 5-HT and Phe were weak. Propofol induced dose-dependent relaxation of artery rings precontracted by the high $K^+$ solution. Propofol also induced relaxation of rings precontracted by U46619 in an endothelium-independent way. Propofol at different concentrations significantly inhibited the $Ca^{2+}$-induced contractions of pulmonary rings exposed to high $K^+$-containing and $Ca^{2+}$-free solution in a dose-dependent manner. Propofol relaxed vessels precontracted by the high $K^+$ solution and U46619 in an endothelium-independent way. The mechanism for this effect may involve inhibition of calcium influx through voltage-operated calcium channels (VOCCs) and receptor-operated calcium channels (ROCCs).

• The Korean Journal of Physiology and Pharmacology
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• 제15권5호
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• pp.279-283
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• 2011

Quercetin (3,3',4',5,7-pentahydroxyflavone) is an attractive therapeutic flavonoid for cancer treatment because of its beneficial properties including apoptotic, antioxidant, and antiproliferative effects on cancer cells. However, the exact mechanism of action of quercetin on ion channel modulation is poorly understood in bladder cancer 253J cells. In this study, we demonstrated that large conductance $Ca^{2+}$-activated $K^+$ ($BK_{Ca}$) or MaxiK channels were functionally expressed in 253J cells, and quercetin increased $BK_{Ca}$ current in a concentration dependent and reversible manner using a whole cell patch configuration. The half maximal activation concentration ($IC_{50}$) of quercetin was $45.5{\pm}7.2{\mu}m$. The quercetin-evoked $BK_{Ca}$ current was inhibited by tetraethylammonium (TEA; 5 mM) a non-specific $BK_{Ca}$ blocker and iberiotoxin (IBX; 100 nM) a $BK_{Ca}$-specific blocker. Quercetin-induced membrane hyperpolarization was measured by fluorescence-activated cell sorting (FACS) with voltage sensitive dye, bis (1,3-dibutylbarbituric acid) trimethine oxonol ($DiBAC_4$2(3); 100 nM). Quercetin-evoked hyperpolarization was prevented by TEA. Quercetin produced an antiproliferative effect ($30.3{\pm}13.5%$) which was recovered to $53.3{\pm}10.5%$ and $72.9{\pm}3.7%$ by TEA and IBX, respectively. Taken together our results indicate that activation of $BK_{Ca}$ channels may be considered an important target related to the action of quercetin on human bladder cancer cells.