• The Korean Journal of Physiology and Pharmacology
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• 제12권1호
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• pp.7-12
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• 2008

OLETF (Otsuka Long-Evans Tokushima Fatty) rats are characterized by obesity-related insulin resistance, which is a phenotype of type 2 diabetes. Sulfonylurea drugs or benzoic acid derivatives as inhibitors of the ATP-sensitive potassium $(K_{ATP})$ channel are commercially available to treat diabetes. The present study compared sulfonylurea drugs (glimepiride and gliclazide) with one of benzoic acid derivatives (repaglinide) in regard to their long-term effect on ameliorating insulin sensitivity in OLETF rats. Each drug was dissolved and fed with drinking water from 29 weeks of age. On high glucose loading at 45 weeks of age, response of blood glucose recovery was the greatest in the group treated with glimepiride. On immunohistochemistry analysis for the Kir6.2 subunit of $K_{ATP}$ channels, insulin receptor ${\beta}$-subunits, and glucose transporters (GLUT) type 2 and 4 in liver, fat and skeletal muscle tissues, the sulfonylurea drugs (glimepiride and gliclazide) were more effective than repaglinide in recovery from their decreased expressions in OLETF rats. From these results, it seems to be plausible that $K_{ATP}$-channel inhibitors containing sulfonylurea moiety may be much more effective in reducing insulin resistance than those with benzoic acid moiety. In contrast to gliclazide, non-tissue selectivity of glimepiride on $K_{ATP}$ channel inhibition may further strengthen an amelioration of insulin sensitivity unless considering other side effects.

• The Korean Journal of Physiology and Pharmacology
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• 제9권4호
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• pp.209-213
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• 2005

Interstitial cells of Cajal (ICCs) are the pacemaker cells that generate slow waves in the gastrointestinal (GI) tract. In the present study, we investigated the effect of mitochondrial ATP-sensitive potassium (mitoKATP) channel on pacemaking activity in cultured ICCs from murine small intestine by using whole-cell patch clamp techniques. Under current clamp mode, at 10μM glibenclamide, there was no change in pacemaking activity of ICCs. At $30{\mu}M$ glibenclamide, an inhibitor of the ATP sensitive $K^+$ channels, we could find two examples. If pacemaking activity of ICCs was irregulating, pacemaking activity of ICCs was changed into regulating and if in normal conditions, membrane potential amplitude was increased. At $50{\mu}M$ glibenclamide, the resting membrane potential was depolarized. At 3mM 5-HDA, an inhibitor of the mitoKATP channels, inhibited the pacemaking activity of ICCs. Both the amplitude and the frequency were decreased. At 5 mM 5-HDA, both the amplitude and the frequency were completely abolished. Diazoxide, an opener of the mitoKATP channels, was applied to examine its effect on pacemaking activity of ICCs. At $50{\mu}M$ concentration, the pacemaking activity of ICCs was inhibited. Both the amplitude and the frequency were decreased. At 1 mM concentration, both the amplitude and the frequency were completely abolished and the resting membrane potential was shaked.These results indicate that mitoKATP channel has an important role in pacemaking activity of ICCs.

• Journal of Yeungnam Medical Science
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• 제11권2호
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• pp.363-374
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• 1994

흰쥐의 적출 배뇨근에 대한 수종의 potassium 통로개방제의 작용을 관찰하고, 배뇨근에 존재하는 potassium 통로의 특성을 알아보기 위하여 체중 250~350g의 흰쥐 (Sprague-Dawley)를 단두하여 희생시킨 후 방광을 적출하였다. 적출된 방광으로 부터 $1.5mm{\times}1.5cm$의 배뇨근 수평절편을 만들어 1ml의 Tyrode 영양액을 포함하는 적출근편실험조에 현수하고 등척성장력을 측정하여 polygraph에 묘기하였다. 배뇨근절편은 potassium 통로 개방제인 pinacidil, BRL 38227 및 RP 52891의 누적 농도 첨가에 의하여 그 기본장력이 농도의존적으로 감소하였는데 그 작용강도는 RP 52891, pinacidil 그리고 BRL 38227의 순이었다. 전위 의존성 potassium 통로 봉쇄제인 procaine은 배뇨근 절편의 기본장력에 영향을 미치지 못했으며, pinacidil, BRL 38227 및 RP 52891에 의한 기본장력감소작용에 대해서도 영향을 미치지 못하였다. 칼슘 의존성 potassium 통로봉쇄제인 apamin은 배뇨근의 기본장력에 유의한 변화를 가져오지 못하였고, potassium 통로 개방제들에 대하여는 상경적 길항작용을 나타내지는 않았으나 BRL 38227과 RP 52891의 최고효능을 유의하게 감소시켰다. ATP 의존성 potassium 통로봉쇄제인 glibenclamide는 배뇨근 절편의 기본장력을 증가시키고, pinacidil을 상경적으로 길항하였으며, BRL 38227과 RP 52891을 상경적으로 길항하는 동시에 그 최대효능을 감소시켰다. 췌장의 ${\beta}$-세포에서 ATP 의존성 potassium 통로를 개방시켜 인슐린의 분비를 억제하는 galanin은 흰쥐의 배뇨근을 수축시켰다. 이상의 결과를 종합하면, 흰쥐의 배뇨근에서는 새로운 potassium 통로 개방제인 RP 52891의 배뇨근 이완작용이 pinacidil보다 강한 것으로 관찰되었다. 또 흰쥐 배뇨근에서는 ATP 의존성이며, glibenclamide 반응성인 potassium 통로가 존재 한다고 생각되는데, 이는 췌장의 ${\beta}$-세포에 있는 ATP 의존성 potassium 통로와는 다른 특성을 가진 것으로 추측된다.

• 한국의학물리학회지:의학물리
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• 제25권3호
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• pp.157-166
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• 2014

뉴론에서 ATP는 분비 과립내에 신경전달물질과 함께 다량 저장되어 있다가 신경전달물질과 함께 분비되는 것으로 알려져 있으므로 신경전달물질의 자극-분비(stimulus-secretion) coupling 과정에 있어 중요한 조절작용을 할 것으로 기대된다. 그러므로 본 연구에서는 뉴론과 그 발생학적 기원이 동일한 부신수질 세포(adrenal chromaffin cell)를 대상으로 하여 세포막 칼슘통로를 통한 세포막 전류에 미치는 ATP의 영향을 측정함으로써 신경전달물질이 자극-분비 coupling 과정에 작용하는 ATP의 조절 작용을 알아보고자 하였다. 부신수질 세포의 칼슘통로를 통한 세포막 전류는 패치클램프 테크닉으로 기록하였다. 10 mM $Ba^{2+}$을 포함한 세포 외 용액에서, $Ba^{2+}$ current는 0.1 mM ATP를 세포외부에 처치했을 때, 평균 $36{\pm}6%$ (n=6) 감소되어 나타났고 ATP를 씻어준 후 전류는 다시 회복되는 가역적 반응을 보였다. ATP의 전류 억제 기전을 알아보고자 칼슘통로에서 관찰되는 현상 중의 하나인 소통(facilitation)현상을 기록하였다. +80 mV의 큰 prepulse를 준 후 바로 테스트 펄스를 주며 측정한 전류는 큰 prepulse에 의해 억제효과가 풀리는(disinhibition) 현상을 나타내었다. ATP 처치 후 큰 자극을 주어 $37{\pm}5%$ (n=11)의 $Ba^{2+}$ 전류 증가가 있었고 이는 ATP가 없는 상태에서 순수하게 큰 자극에 의해 소통되는 $25{\pm}3%$ (n=12)과 유의한 차이를 보였다(p<0.05). ATP의 억제 기전이 G-protein을 매개로 한 것인지를 알아보고자 가수분해 되지 않는 GTP 유도체인 $GTP{\gamma}S$를 세포 내에 준 후 $Ba^{2+}$ 전류를 기록하였다. $GTP{\gamma}S$에 의해 55%의 전류 크기의 감소가 있었고 이 환경에서 큰 prepulse를 인가하였을 때 $34{\pm}4%$ (n=19)의 소통현상을 보였다. 이는 $GTP{\gamma}S$가 없는 환경에서의 $25{\pm}3%$ (n=12)의 소통현상을 보인 것과 유의한 차이를 보였다(p<0.05). $Ba^{2+}$ current trace의 활성화 과정(activation)을 curve-fitting한 결과, control은 single exponential curve로 fitting된 반면, ATP 또는 $GTP{\gamma}S$를 처치한 경우, 그리고 ATP와 $GTP{\gamma}S$ 모두 처치한 경우에서는 double-exponential curve로 가장 잘 fitting이 되었다. 즉, ATP나 $GTP{\gamma}S$를 처치했을 때 모두 전류가 더 느리게 활성화되는 모양을 나타내었고, 이상의 결과로 미루어 ATP와 $GTP{\gamma}S$는 같은 방식으로 칼슘통로를 억제하고, 이러한 억제효과는 세포막에 아주 큰 전압을 걸어주면 칼슘 통로에 결합했던 G-protein이 막전압 의존적으로 떨어짐으로써 소실(disinhibition)된다고 해석된다. 본 연구에서 확인한 ATP의 칼슘통로 억제효과는 자체 크로마핀 세포 또는 주변 세포에서 아드레날린이 적게 분비되게 하는 autocrine 또는 paracrine inhibition 과정의 중요한 기전으로 작용할 것이다.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 1997년도 학술발표회
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• pp.11-12
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• 1997

A concept that extracellular ATP plays a role as a neurotransmitter is now widely accepted. ATP released from nerve terminals transmits both excitatory and inhibitory signals to postsynaptic neurons, muscle cells, and non-excitable cells. ATP-activated channels are effectors that convert the binding of ATP into the opening of ion channel pores in postsynaptic membrane.(omitted)

• Journal of Ginseng Research
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• 제23권4호
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• pp.235-238
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• 1999

[ $K_{ATP}$ ]채널은 세포내 ATP에 의해서 억제되는 포타슘 채널로서 혈관평활근, 골격근 및 체장의 ${\beta}$세포 막에 존재하여, 근세포의 막전압 조절을 통하여 근수축 및 이완을 조절할 뿐만 아니라 췌장의 ${\beta}$세포로부터 인슐린분비를 조절한다. 홍삼 복합사포닌 및 사포닌 $Rg_3$ 성분은 토끼 관상동맥 평활근세포의 칼슘의존성-포타슘채널$(BK_{Ca})$의 활성을 증가시켜 막전압의 과분극을 유발하여 혈관평활근을 이완시킨다. 사포닌 $Rg_3$성분은 홍삼의 복합사포닌 성분보다 $BK_{Ca}$에 더 높은 활성을 보이기 때문에 본 연구는 사포닌 $Rg_3$성분이 토끼 관상동맥 단일 평활근세포의 ${\beta}$채널의 활성도를 조절하는지를 팻치클램프 방법으로 기록하였다. 막전압 의존성과 함께 내향전류(inward rectification)특성을 보이는 ${\beta}$채널의 활성을 토끼 관상동맥 평활근 세포로부터 기록하였다. 이 ${\beta}$채널은 ATP와 giyburide에 의해서 억제되었으며 minoxidil에 의해서 활성이 증가되었다. 홍삼 사포닌 $Rg_3$성분은 $K_{ATP}$채널의 전류극대치에는 영향을 주지 않고 전류의 inactivation을 억제시켜 결과적으로 $K_{ATP}$채널의 활성을 증가시켰으며, 단일 KhTr채널이 열리는 시간도 증가시켰다. 따라서 본 실험 결과는 사포닌 $Rg_3$성분이 KATP채널의 활성을 증가시켜 막전압을 조절하여 관상동맥 평활근의 이완을 촉진한다고 여겨진다.

• The Korean Journal of Physiology and Pharmacology
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• 제1권6호
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• pp.783-796
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• 1997

The relaxation induced by stimulation of the inhibitory non-adrenergic, non-cholinergic (iNANC) nerve is mediated by the release of iNANC neurotransmitters such as nitric oxide (NO), vasoactive intestinal peptide (VIP) and adenosine triphosphate (ATP). The mechanisms of NO, VIP or ATP-induced relaxation have been partly determined in previous studies, but the detailed mechanism remains unknown. We tried to identify the nature of iNANC neurotransmitters in the smooth muscle of guinea pig ileum and to determine the mechanism of the inhibitory effect of nitric oxide. We measured the effect of NO-donors VIP and ATP on the intracellular $Ca^{2+}$ concentration$([Ca^{2+}]_i)$, by means of a fluorescence dye(fura 2) and tension simultaneously in the isolated guinea pig ileal smooth muscle. Following are the results obtained. 1. Sodium nitroprusside $(SNP:10^{-5}\;M)$ or S -nitro-N-acetyl-penicillamine $(SNP:10^{-5}\;M)$ decreased resting $[Ca^{2+}]_i$ I and tension of muscle. SNP or SNAP also inhibited rhythmic oscillation of $[Ca^{2+}]_i$ and tension. In 40mM $K^+$ solution or carbachol ($(CCh:10^{-6}\;M)$-induced precontracted muscle, SNP decreased muscle tension. VIP did not change $[Ca^{2+}]_i$ and tension in the resting or precontracted muscle, but ATP increased resting $[Ca^{2+}]_i$ and tension in the resting muscle. 2. 1H-[1,2,4]oxadiazol(4,3-a)quinoxalin-1-one $(ODQ:1\;{\mu}M)$, a specific inhibitor of soluble guanylate cyclase, limited the inhibitory effect of SNP 3. Glibenclamide $(10\;{\mu}M)$, a blocker of $K_{ATP}$ channel, and 4-aminopyridine (4-AP:5 mM), a blocker of delayed rectifier K channel, apamin $(0.1\;{\mu}M)$, a blocker of small conductance $K_{Ca}$ channel had no effect on the inhibitory effect of SNP. Iberiotoxin $(0.1\;{\mu}M)$, a blocker of large conductance $K_{Ca}$ channel, significantly increased the resting $[Ca^{2+}]_i$, and tension, and limited the inhibitory effect of SNP. 4. Nifedipine $(1\;{\mu}M)$ or elimination of external $Ca^{2+}$ decreased not only resting $[Ca^{2+}]_i$ and tension but also oscillation of $[Ca^{2+}]_i$ and tension. Ryanodine $(5\;{\mu}M)$ and cyclopiazonic acid $(10\;{\mu}M)$ decreased oscillation of $[Ca^{2+}]_i$ and tension. 5. SNP decreased $Ca^{2+}$ sensitivity of contractile protein. In conclusion, these results suggest that 1) NO is an inhibitory neurotransmitter in the guinea pig ileum, 2) the inhibitory effect of SNP on the $[Ca^{2+}]_i$ and tension of the muscle is due to a decrease in $[Ca^{2+}]_i$ by activation of the large conductance $K_{Ca}$ channel and a decrease in the sensitivity of contractile elements to $Ca^{2+}$ through activation of G-kinase.

• The Korean Journal of Pain
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• 제25권4호
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• pp.221-227
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• 2012

Background: It has been reported that curcumin, the main active compound of Curcuma longa, also known as turmeric, exhibits antinociceptive properties. The aim of this study was to examine the participation of ATP-sensitive potassium channels ($K_{ATP}$ channels) and, in particular, that of the L-arginine-nitric oxide-cyclic GMP-$K_{ATP}$ channel pathway, in the antinociceptive effect of curcumin. Methods: Pain was induced by the intraplantar injection of 1% formalin in the right hind paw of Wistar rats. Formalin-induced flinching behavior was interpreted as an expression of nociception. The antinociceptive effect of oral curcumin was explored in the presence and absence of local pretreatment with L-NAME, an inhibitor of nitric oxide synthase, ODQ, an inhibitor of soluble guanylyl cyclase, and glibenclamide, a blocker of $K_{ATP}$ channels. Results: Oral curcumin produced a dose-dependent antinociceptive effect in the 1% formalin test. Curcumin-induced antinociception was not altered by local L-NAME or ODQ, but was significantly impaired by glibenclamide. Conclusions: Our results confirm that curcumin is an effective antinociceptive agent. Curcumin-induced antinociception appears to involve the participation of $K_{ATP}$ channels at the peripheral level, as local injection of glibenclamide prevented its effect. Activation of $K_{ATP}$ channels, however, does not occur by activation of the L-arginine-nitric oxide-cGMP-$K_{ATP}$ channel pathway.

• Biomolecules & Therapeutics
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• 제14권2호
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• pp.119-124
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• 2006

This study was performed to investigate the influence of the spinal adenosine $A_1$ receptors on the central regulation of blood pressure (BP) and heart rate (HR), and to define whether its mechanism is mediated by cyclic AMP (cAMP), cyclic GMP (cGMP) or potassium channel. Intrathecal (i.t.) administration of drugs at the thoracic level were performed in anesthetized, artificially ventilated male Sprague-Dawley rats. I.t. injection of adenosine $A_1$ receptor agonist, $N^6$-cyclohexyladenosine (CHA; 1, 5 and 10 nmol) produced dose dependent decrease of BP and HR and it was attenuated by pretreatment of 50 nmol of 8-cyclopentyl-1,3-dimethylxanthine, a specific adenosine $A_1$ receptor antagonist. Pretreatment with a cAMP analogue, 8-bromo-cAMP, also attenuated the depressor and bradycardiac effects of CHA (10 nmol), but not with cGMP analogue, 8-bromo-cGMP. Pretreatment with a ATP-sensitive potassium channel blocker, glipizide (20 nmol) also attenuated the depressor and bradycardiac effects of CHA (10 nmol). These results suggest that adenosine $A_1$ receptor in the spinal cord plays an inhibitory role in the central cardiovascular regulation and that this depressor and bradycardiac actions are mediated by cAMP and potassium channel.

• The Korean Journal of Physiology and Pharmacology
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• 제7권6호
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• pp.341-348
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• 2003

Mechanical stimuli to the cardiac myocytes initiate many biochemical and physiological events. Stretch-activated cation channels have been suggested to mediate these events. In this study, cell-attached and inside-out excised-patch clamp methods were used to identify stretch-activated cation channels in adult rat atrial myocytes. Channel openings were increased in cell-attached configuration when negative pressure was applied to the pipette, and also in inside-out excised patches by negative pressure. The channel was not permeable to $Cl^-$, $Na^+$ and $Cs^+$, but selectively permeable to $K^+$, and the degree of activation was dependent on the magnitude of negative pressure (full activation at ${\sim} -50 mmHg). In symmetrical 140 mM KCl, the slope conductance was $51.2{\pm}3$ pS between the potentials of -80 and 0 mV and $55{\pm}6$ pS between 0 and +80 mV (n=5). Glibenclamide ($100{mu}M$) or ATP (2 mM) failed to block the channel openings, indicating that it is not ATP-sensitive $K^+$ channel. Arachidonic acid ($30{mu}M$), which has been shown to activate a $K^+$ channel cooperatively with membrane stretch, did not affect the channel activity. $GdCl_3$ ($100{mu}M$) also did not alter the activity. These results demonstrate that the mechanical stretch in rat atrial myocytes activates a novel $K^+$-selective cation channel, which is not associated with other $K^+$ channels such as ATP-sensitive and arachidonic acid-activated $K^+$ channel.