• The Korean Journal of Physiology
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• 제23권2호
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• pp.237-252
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• 1989

고양이 회장 종주근에서 세포막 소포를 분리하여 $Na^+$의 농도 경사에 의존하여 일어나는 $Ca^{2+}$ 이동의 특성에 대하여 연구하였다. 막소포 내부에서 외부로 향하는 $Na^+$의 농도 경사 존재시 $Ca^{2+}$의 축적이 현저히 증가하여 $Na^+$ 의존성 $Ca^{2+}$ 축적을 보였으며, 이는 외부용액에 $Na^+$ ionophore인 monensin을 처리시 소실되었다. 한편 이러한 $Ca^{2+}$ 축적의 증가 작용은 $Na^+$에 특이적이었으며 $K^+$, $Li^+$, $Rb^+$, $Cs^+$ 및 choline이온은 $Na^+$의 작용을 대치하지 못하였다. $Ba^{2+}$, $Sr^{2+}$, $Mn^{2+}$ 및 $Cd^{2+}$ 등의 2가 양이온들은 0.5 mM의 농도에서 $Na^+$ 의존성 $Ca^{2+}$ 축적을 억제하였으나 $Mg^{2+}$은 이 농도에서 억제 효과를 보이지 않았다. 막소포 외부의 pH를 pH 6.0에서 8.5까지 증가시 $Na^+$ 의존성 $Ca^{2+}$ 축적이 증가하였다. Amiloride는 0.5 mM 이상의 농도에서 $Na^+$ 의존성 $Ca^{2+}$ 축적을 유의하게 억제하였으나 diltiazem 및 vanadate는 이 농도에서 유의한 억제효과를 보이지 않았다. 동력학적으로 분석하여 측정한 $Na^+$ 의존성 $Ca^{2+}$ 축적의 $Ca^{2+}$에 대한 $K_m$ 값은 $18.2\;{\mu}M$이었으며 5초에서 측정한 $V_{max}$값은 689.7 pmole/mg protein이었다. $Ca^{2+}$ 축적에 대한 $Na^+$ 농도 경사의 효과를 동력학적으로 분석한 결과 막소포 외부에서의 $Ca^{2+}$에 대한 친화도에는 변화없이 최고 이동치만 증가시켜 전형적인 비상경적 작용 양상을 보였다. $Ca^{2+}$ 축적에 대한 $Na^+$ 농도 경사의 효과를 $Na^+$ 농도에 따라 측정하여 Hill plot을 시행한 결과 Hill coefficient가 2.52로 나타났다. 막소포 내부로 향하는 $K^+$ 농도 경사하에서 valinomycin을 처리하여 막소포 내부에 양전위를 발생시킨 결과 $Na^+$ 의존성 $Ca^{2+}$ 축적이 증가하였다. 이와 같은 결과들은 고양이 회장 평활근에서 분리한 세포막에 $Na^{+}-Ca^{2+}$ 교환기전이 존재하고 이는 다른 조직에서 밝혀진 것과 유사한 특성을 지녔으며 electrogenic한 기전으로 작용할 가능성을 시사하였다.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1994년도 춘계학술대회 and 제3회 신약개발 연구발표회
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• pp.290-290
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• 1994

The binding characteristic of oxomemazine to muscarinic receptor in the cerebrum, heart, and ileum were compared to those of pirenzepine to investigate whether oxomemazine could classify the muscarinic receptor subtypes. 〔$^3$H〕Quinucl idinyl benzilate(QNB) identified a single class of muscarinic receptors with apparent K$\sub$D/ value of about 60 pM in three tissues. Analysis of the pirenzepine inhibition curve of 〔$^3$H〕QNB binding to cerebral microsome indicated the presence of two receptor subtypes with high (Ki=16 nM, M$_1$-receptor) and low (Ki=400 nM, M$_2$-receptor) affinity for pirenzepine. Oxomemazine also identified two receptor subtypes with high (Ki=84 nM, On-receptor) and low (Ki=1 4 ${\mu}$M, O$\sub$L/-receptor) affinity in rat cerebral microsome, The percentage population of the M$_1$-and M$_2$-receptors to the total receptors were 61 : 39, and those of the O$\^$H/- and O$\sub$L/-receptors 39 : 61, respectively, However, the Hill coefficients of these two drugs for the inhibition of 〔$^3$H〕QNB binding to the heart and ileum were close to unity which indicated that these drugs bound to a uniform population of receptors in these two tissues. The Ki values for the low affinity sites of pirenzepine and oxomemazine in the cerebrum were similar to those of these drugs in the heart ileum. Both pirenzepine and oxomemazine increased K$\sub$D/ value for 〔$^3$H〕QNB without affecting the binding sites concentration and Hill coefficient for the 〔$^3$H〕QNB binding. Oxomemazine had a 10-fold lower affinity at Ma-receptors than at M$_1$-receptors, and pirenzepine a 8-fold lower affinity at O$\sub$L/-receptors than OH-receptors. Analysis of the shal low competition curves of oxomemazine for the H$_1$ receptors and pirenzepine for the O$\sub$L/-receptors yielded that 69% of the M$_1$-receptors were of the O$\sub$H/-receptors and the remaining 31% of the O$\sub$L/-receptors, and that 29% of the O$\sub$L/-receptors were of the M$_1$-receptors and 71% of the M$_2$-receptors. However, M$_2$ for oxomemazine and O$\sub$H/ for pirenzepine were composed of a uniform population. These results suggest that oxomemazine could discriminatethe muscarnic receptor subtypes and may subclassify the M$_1$-receptors into two subtypes.

• 한국산림과학회지
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• 제89권3호
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• pp.397-404
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• 2000

임도 옆도랑침식에 영향을 미치는 요인의 평가 및 안정도 판별을 위하여 광릉시험림의 임도를 대상으로 조사를 실시한 결과 침식에 미치는 기여순위는 종단물매, 시설위치, 절토사면경사, 절토사면구성물질, 유하거리, 노면형태, 노면재료, 절토사면피복도, 절토사면길이 순으로 나타났다. 임도 옆도랑침식을 유발하는 요인을 평가하면, 종단물매는 8% 이상, 임도시설위치는 산록(山麓)과 중복(中腹), 절토사면경사는 $50^{\circ}$ 이상, 절토사면토성은 견질토사, 자갈섞인 토사, 호박돌섞인 토사, 유하거리는 80m 이상의 지역에서, 그리고 노면재료는 토사도(土砂道)와 자갈부설도에서, 노면형태의 경우에는 철(凸)형과 직선형, 절토사면 피복도(被覆度)는 피복도가 중(中)이상인 곳에서 임도 옆도랑침식이 발생할 가능성이 높은 것으로 예측(豫測)되었다.

• Asian-Australasian Journal of Animal Sciences
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• 제16권7호
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• pp.946-951
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• 2003

The Genetic diversity and relationship of native Siri (Bos indicus) cattle populations of Bhutan were evaluated using 20 microsatellite markers. A total of 120 Siri cattle were sampled and were grouped into four populations according to their geographical locations which were named Siri West, Siri South, Siri Central and Siri East cattle. For each, 30 individuals were sampled. In addition, 30 samples each of Indian Jaba (B. indicus), Tibetan Goleng (B. taurus), Nepal Hill cattle (B. indicus), Holstein Friesian (B.taurus) and Mithun (B. frontalis) were typed. The mean number of alleles per loci (MNA) and observed heterozygosity (Ho) were high in the Siri populations ($MNA=7.2{\pm}0.3$ to $8.9{\pm}0.5$ and $Ho=0.67{\pm}0.04$ to $0.73{\pm}0.03$). The smallest coefficient of genetic differentiation and genetic distance ($F_{ST}=0.015$ and $D_A=0.073$) were obtained between Siri West and Siri Central populations. Siri East population is genetically distinct from the other Siri populations being close to the Indian Jaba ($F_{ST}=0.024$ and $D_A=0.084$). A high bootstrap value of 96% supported the close relationship of Siri South, Siri Central and Siri West, while the relationship between Siri East and Jaba was also supported by a high bootstrap value (82%). Data from principal component analysis and individual assignment test were in concordance with the inference from genetic distance and differentiation. In conclusion we identified two separate Siri cattle populations in Bhutan at the genetic level. One population included Siri cattle sampled from the West, Central and South of the country and the other Siri cattle was sampled from the East of the country. We suggest that Siri cattle conservation program in Bhutan should focus on the former population as it has received less genetic influence from other cattle breeds.

• The Korean Journal of Physiology and Pharmacology
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• 제21권4호
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• pp.415-421
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• 2017

We investigated the inhibitory effect of escitalopram, a selective serotonin reuptake inhibitor (SSRI), on voltage-dependent $K^+$ (Kv) channels in freshly separated from rabbit coronary arterial smooth muscle cells. The application of escitalopram rapidly inhibited vascular Kv channels. Kv currents were progressively inhibited by an increase in the concentrations of escitalopram, suggesting that escitalopram inhibited vascular Kv currents in a concentration-dependent manner. The $IC_{50}$ value and Hill coefficient for escitalopram-induced inhibition of Kv channels were $9.54{\pm}1.33{\mu}M$ and $0.75{\pm}0.10$, respectively. Addition of escitalopram did not alter the steady-state activation and inactivation curves, suggesting that the voltage sensors of the channels were not affected. Pretreatment with inhibitors of Kv1.5 and/or Kv2.1 did not affect the inhibitory action of escitalopram on vascular Kv channels. From these results, we concluded that escitalopram decreased the vascular Kv current in a concentration-dependent manner, independent of serotonin reuptake inhibition.

• The Korean Journal of Physiology and Pharmacology
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• 제21권2호
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• pp.225-232
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• 2017

We demonstrated the effect of nortriptyline, a tricyclic antidepressant drug and serotonin reuptake inhibitor, on voltage-dependent $K^+$ (Kv) channels in freshly isolated rabbit coronary arterial smooth muscle cells using a whole-cell patch clamp technique. Nortriptyline inhibited Kv currents in a concentration-dependent manner, with an apparent $IC_{50}$ value of $2.86{\pm}0.52{\mu}M$ and a Hill coefficient of $0.77{\pm}0.1$. Although application of nortriptyline did not change the activation curve, nortriptyline shifted the inactivation current toward a more negative potential. Application of train pulses (1 or 2 Hz) did not change the nortriptyline-induced Kv channel inhibition, suggesting that the effects of nortiprtyline were not use-dependent. Preincubation with the Kv1.5 and Kv2.1/2.2 inhibitors, DPO-1 and guangxitoxin did not affect nortriptyline inhibition of Kv channels. From these results, we concluded that nortriptyline inhibited Kv channels in a concentration-dependent and state-independent manner independently of serotonin reuptake.

• The Korean Journal of Physiology and Pharmacology
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• 제21권2호
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• pp.169-177
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• 2017

Lamotrigine is an antiepileptic drug widely used to treat epileptic seizures. Using whole-cell voltage clamp recordings in combination with a fast drug application approach, we investigated the effects of lamotrigine on 5-hydroxytryptamine $(5-HT)_3$ receptors in NCB-20 neuroblastoma cells. Co-application of lamotrigine ($1{\sim}300{\mu}M$) resulted in a concentration-dependent reduction in peak amplitude of currents induced by $3{\mu}m$ of 5-HT for an $IC_{50}$ value of $28.2{\pm}3.6{\mu}M$ with a Hill coefficient of $1.2{\pm}0.1$. These peak amplitude decreases were accompanied by the rise slope reduction. In addition, $5-HT_3$-mediated currents evoked by 1 mM dopamine, a partial $5-HT_3$ receptor agonist, were inhibited by lamotrigine co-application. The $EC_{50}$ of 5-HT for $5-HT_3$ receptor currents were shifted to the right by co-application of lamotrigine without a significant change of maximal effect. Currents activated by 5-HT and lamotrigine co-application in the presence of 1 min pretreatment of lamotrigine were similar to those activated by 5-HT and lamotrigine co-application alone. Moreover, subsequent application of lamotrigine in the presence of 5-HT and 5-hydroxyindole, known to attenuate $5-HT_3$ receptor desensitization, inhibited $5-HT_3$ receptor currents in a concentration-dependent manner. The deactivation of $5-HT_3$ receptor was delayed by washing with an external solution containing lamotrigine. Lamotrigine accelerated the desensitization process of $5-HT_3$ receptors. There was no voltage-dependency in the inhibitory effects of lamotrigine on the $5-HT_3$ receptor currents. These results indicate that lamotrigine inhibits $5-HT_3$-activated currents in a competitive manner by binding to the open state of the channels and blocking channel activation or accelerating receptor desensitization.

• The Korean Journal of Physiology and Pharmacology
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• 제5권2호
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• pp.165-175
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• 2001

Background: Recent in vivo experimental evidence suggests that isoflurane-induced cardioprotection may involve $K_{ATP}$ channel activation. However, it was demonstrated that isoflurane inhibited $K_{ATP}$ channel activities in the inside-out patch mode. To explain this discrepancy, the present investigation tested the hypothesis that a metabolite of isoflurane, trifluoroacetic acid (TFA), contributes to isoflurnae-induced cardioprotection via $K_{ATP}$ channel activation during myocardial ischemia and reperfusion. Methods: Single ventricular myocytes were isolated from rabbit hearts by an enzymatic dissociation procedure. Patch-clamp techniques were used to record single-channel currents. $K_{ATP}$ channel activities were assessed before and after the application of TFA with the inside-out patch mode. Results: TFA enhanced channel activity in a concentration-dependent fashion. The concentration of TFA for half-maximal activation and the Hill coefficient were 0.03 mM and 1.2, respectively. TFA did not affect the single channel conductance of $K_{ATP}$ channels. Analysis of open and closed time distributions showed that TFA increased burst duration and decreased the interburst interval without changes in open and closed time distributions shorter than 5 ms. TFA diminished ATP sensitivity of $K_{ATP}$ channels in a concentration-response relationship for ATP. Conclusions: TFA, a metabolite of isoflurane, enhanced $K_{ATP}$ channel activity in a concentration-dependent fashion. These results imply that TFA could mediate isoflurane-induced cardioprotection via $K_{ATP}$ channel activation during myocardial ischemia and reperfusion.

• The Korean Journal of Physiology and Pharmacology
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• 제20권2호
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• pp.193-200
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• 2016

Sertraline, a selective serotonin reuptake inhibitor (SSRI), has been reported to lead to cardiac toxicity even at therapeutic doses including sudden cardiac death and ventricular arrhythmia. And in a SSRI-independent manner, sertraline has been known to inhibit various voltage-dependent channels, which play an important role in regulation of cardiovascular system. In the present study, we investigated the action of sertraline on Kv1.5, which is one of cardiac ion channels. The effect of sertraline on the cloned neuronal rat Kv1.5 channels stably expressed in Chinese hamster ovary cells was investigated using the whole-cell patch-clamp technique. Sertraline reduced Kv1.5 whole-cell currents in a reversible concentration-dependent manner, with an $IC_{50}$ value and a Hill coefficient of $0.71{\mu}M$ and 1.29, respectively. Sertraline accelerated the decay rate of inactivation of Kv1.5 currents without modifying the kinetics of current activation. The inhibition increased steeply between -20 and 0 mV, which corresponded with the voltage range for channel opening. In the voltage range positive to +10 mV, inhibition displayed a weak voltage dependence, consistent with an electrical distance ${\delta}$ of 0.16. Sertraline slowed the deactivation time course, resulting in a tail crossover phenomenon when the tail currents, recorded in the presence and absence of sertraline, were superimposed. Inhibition of Kv1.5 by sertraline was use-dependent. The present results suggest that sertraline acts on Kv1.5 currents as an open-channel blocker.

• The Korean Journal of Physiology and Pharmacology
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• 제21권1호
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• pp.75-82
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• 2017

The effects of acepromazine on human ether-$\grave{a}$-go-go-related gene (hERG) potassium channels were investigated using whole-cell voltage-clamp technique in human embryonic kidney (HEK293) cells transfected with hERG. The hERG currents were recorded with or without acepromazine, and the steady-state and peak tail currents were analyzed for the evaluating the drug effects. Acepromazine inhibited the hERG currents in a concentration-dependent manner with an $IC_{50}$ value of $1.5{\mu}M$ and Hill coefficient of 1.1. Acepromazine blocked hERG currents in a voltage-dependent manner between -40 and +10 mV. Before and after application of acepromazine, the half activation potentials of hERG currents changed to hyperpolarizing direction. Acepromazine blocked both the steady-state hERG currents by depolarizing pulse and the peak tail currents by repolarizing pulse; however, the extent of blocking by acepromazine in the repolarizing pulse was more profound than that in the depolarizing pulse, indicating that acepromazine has a high affinity for the open state of the channels, with a relatively lower affinity for the closed state of hERG channels. A fast application of acepromazine during the tail currents inhibited the open state of hERG channels in a concentration-dependent. The steady-state inactivation of hERG currents shifted to the hyperpolarized direction by acepromazine. These results suggest that acepromazine inhibits the hERG channels probably by an open- and inactivated-channel blocking mechanism. Regarding to the fact that the hERG channels are the potential target of drug-induced long QT syndrome, our results suggest that acepromazine can possibly induce a cardiac arrhythmia through the inhibition of hERG channels.