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1.
背景:在运动生理状态下,KATP 在调节冠状动脉张力、运动诱导心肌保护效应和延缓骨骼肌疲劳等多个方面具有重要作用。目的:对KATP在运动中的作用进行了综述和探讨,以期为深入了解运动调节机体代谢提供理论参考。方法:检索1991年1月至2014年6月 PubMed数据库及维普中文科技数据库文献。英文检索词为“KATP Channels;Adenosine Triphosphate;Sports;Myocardium;Ion Channels”,中文检索词为“KATP通道;三磷酸腺苷;运动;心肌;离子通道”。选择与KATP分子结构、生物学功能及调控相关,以及KATP与冠状动脉、心肌、骨骼肌疲劳及运动能力相关的文献42篇文献进行探讨。结果与结论:ATP敏感性钾离子通道可以偶联细胞内能量代谢和细胞膜兴奋性,在应对各种生理和病理应激时是保护心肌的效应器之一。长期的耐力训练则会增加骨骼肌和心肌KATP的表达,可能是心肌和骨骼肌对运动应激产生的一种适应性表现。KATP 可能参与冠状动脉血流量的调节。在运动诱导的减轻心肌缺血再灌注损伤的保护效应中,心肌KATP具有重要作用。当骨骼肌疲劳发生时,KATP的激活有利于防止ATP的过度消耗而造成肌纤维损伤和细胞死亡,有利于疲劳的快速恢复。关于KATP与运动能力的关系仍需进一步的研究。  相似文献   

2.
Hypokalemic periodic paralysis (HOPP) is a rare disease associated with attacks of muscle weakness and hypokalemia. In the present study, immunoprecipitation/Western blotting has shown that a HOPP patient was deficient in sarcolemmal KATP channels. Real‐time RT‐PCR has revealed that HOPP has decreased mRNA levels of Kir6.2, a pore‐forming KATP channel subunit, without affecting the expression of other KATP channel‐forming proteins. Based on these findings, we conclude that HOPP could be associated with impaired expression of Kir6.2 which leads to deficiency in skeletal muscle KATP channels, which may explain the symptoms and clinical signs of this disease.  相似文献   

3.
Sympathetic vasoconstriction is sensitive to inhibition by metabolic events in contracting rat and human skeletal muscle, but the underlying cellular mechanisms are unknown. In rats, this inhibition involves mainly alpha2-adrenergic vasoconstriction, which relies heavily on Ca2+ influx through voltage-dependent Ca2+ channels. We therefore hypothesized that contraction-induced inhibition of sympathetic vasoconstriction is mediated by ATP-sensitive potassium (KATP) channels, a hyperpolarizing vasodilator mechanism that could be activated by some metabolic product(s) of skeletal muscle contraction. We tested this hypothesis in anesthetized rats by measuring femoral artery blood flow responses to lumbar sympathetic nerve stimulation or intraarterial hindlimb infusion of the specific alpha2-adrenergic agonist UK 14,304 during KATP channel activation with diazoxide in resting hindlimb and during KATP channel block with glibenclamide in contracting hindlimb. The major new findings are twofold. First, like muscle contraction, pharmacologic activation of KATP channels with diazoxide in resting hindlimb dose dependently attenuated the vasoconstrictor responses to either sympathetic nerve stimulation or intraarterial UK 14,304. Second, the large contraction-induced attenuation in sympathetic vasoconstriction elicited by nerve stimulation or UK 14,304 was partially reversed when the physiologic activation of KATP channels produced by muscle contraction was prevented with glibenclamide. We conclude that contraction-induced activation of KATP channels is a major mechanism underlying metabolic inhibition of sympathetic vasoconstriction in exercising skeletal muscle.  相似文献   

4.
5.
ATP-sensitive potassium channels (K(ATP) channels) are heteromeric complexes of pore-forming inwardly rectifying potassium channel subunits and regulatory sulfonylurea receptor subunits. K(ATP) channels were identified in a variety of tissues including muscle cells, pancreatic beta-cells, and various neurons. They are regulated by the intracellular ATP/ADP ratio; ATP induces channel inhibition and MgADP induces channel opening. Functionally, K(ATP) channels provide a means of linking the electrical activity of a cell to its metabolic state. Shortening of the cardiac action potential, smooth muscle relaxation, inhibition of both insulin secretion, and neurotransmitter release are mediated via K(ATP) channels. Given their many physiological functions, K(ATP) channels represent promising drug targets. Sulfonylureas like glibenclamide block K(ATP) channels; they are used in the therapy of type 2 diabetes. Openers of K(ATP) channels (KCOs), for example, relax smooth muscle and induce hypotension. KCOs are chemically heterogeneous and include as different classes as the benzopyrans, cyanoguanidines, thioformamides, thiadiazines, and pyridyl nitrates. Examples for new chemical entities more recently developed as KCOs include cyclobutenediones, dihydropyridine related structures, and tertiary carbinols.  相似文献   

6.
Hypokalemic periodic paralysis (HypoPP) is an ion channelopathy of skeletal muscle characterized by attacks of muscle weakness associated with low serum K+. HypoPP results from a transient failure of muscle fiber excitability. Mutations in the genes encoding a calcium channel (CaV1.1) and a sodium channel (NaV1.4) have been identified in HypoPP families. Mutations of NaV1.4 give rise to a heterogeneous group of muscle disorders, with gain-of-function defects causing myotonia or hyperkalemic periodic paralysis. To address the question of specificity for the allele encoding the NaV1.4-R669H variant as a cause of HypoPP and to produce a model system in which to characterize functional defects of the mutant channel and susceptibility to paralysis, we generated knockin mice carrying the ortholog of the gene encoding the NaV1.4-R669H variant (referred to herein as R669H mice). Homozygous R669H mice had a robust HypoPP phenotype, with transient loss of muscle excitability and weakness in low-K+ challenge, insensitivity to high-K+ challenge, dominant inheritance, and absence of myotonia. Recovery was sensitive to the Na+/K+-ATPase pump inhibitor ouabain. Affected fibers had an anomalous inward current at hyperpolarized potentials, consistent with the proposal that a leaky gating pore in R669H channels triggers attacks, whereas a reduction in the amplitude of action potentials implies additional loss-of-function changes for the mutant NaV1.4 channels.  相似文献   

7.
Hyperkalemic periodic paralysis (HyperKPP) produces myotonia and attacks of muscle weakness triggered by rest after exercise or by K+ ingestion. We introduced a missense substitution corresponding to a human familial HyperKPP mutation (Met1592Val) into the mouse gene encoding the skeletal muscle voltage-gated Na+ channel NaV1.4. Mice heterozygous for this mutation exhibited prominent myotonia at rest and muscle fiber-type switching to a more oxidative phenotype compared with controls. Isolated mutant extensor digitorum longus muscles were abnormally sensitive to the Na+/K+ pump inhibitor ouabain and exhibited age-dependent changes, including delayed relaxation and altered generation of tetanic force. Moreover, rapid and sustained weakness of isolated mutant muscles was induced when the extracellular K+ concentration was increased from 4 mM to 10 mM, a level observed in the muscle interstitium of humans during exercise. Mutant muscle recovered from stimulation-induced fatigue more slowly than did control muscle, and the extent of recovery was decreased in the presence of high extracellular K+ levels. These findings demonstrate that expression of the Met1592ValNa+ channel in mouse muscle is sufficient to produce important features of HyperKPP, including myotonia, K+-sensitive paralysis, and susceptibility to delayed weakness during recovery from fatigue.  相似文献   

8.
This study was conducted to examine the role of membrane hyperpolarization in mediating vascular hyporeactivity induced by cecal ligation and puncture (CLP) in endothelial-denuded strips of rat thoracic aorta ex vivo. The CLP for 18 h elicited a significant fall of blood pressure and a severe vascular hyporeactivity to norepinephrine as seen in severe sepsis. At the end of the in vivo experiments, thoracic aortas were removed from both CLP-treated and control rats. After removal of the endothelium, aortic segments were mounted in myographs for the recording of isometric tension and smooth muscle membrane potential. The membrane potential recording showed that a hyperpolarization was observed in the CLP-treated rats when compared with the control rats. This hyperpolarization was reversed by iberiotoxin (a large-conductance Ca2+-activated K+ channel blocker), 4-aminopyridine (a voltage-dependent K+ channel blocker), barium (an inward rectifier K+ channels blocker), N-(1-adamantyl)-N'-cyclohexyl-4-morpholinecarboxamidine hydrochloride (a pore-forming blocker of adenosine triphosphate (ATP)-sensitive K+ channels [KATP]), or methylene blue (a nonspecific guanylyl cyclase [GC] inhibitor). However, this hyperpolarization was not significantly affected by apamin (a small-conductance Ca2+-activated K+ channel blocker), glibenclamide (a sulfonylurea blocker of KATP), N(omega)-nitro-L-arginine methyl ester (a NOS inhibitor), or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (an NO-sensitive GC inhibitor). In addition, the basal tension of the tissues obtained from CLP rats was increased simultaneously, whereas membrane potential was reversed. In contrast, none of these inhibitors had significant effects on the membrane potential or the basal tension in control tissues. Thus, we provide electrophysiological and functional evidence demonstrating that an abnormal activation of K+ channels in vascular smooth muscle in animals with septic shock induced by CLP. Our observations suggest that the activation of large conductance Ca2+-activated K+ channels, voltage-dependent K+ channels, inward rectifier K+ channels, and KATP channels, but not small conductance Ca2+-activated K+ channels, contributes to CLP-induced vascular hyporeactivity. Furthermore, the hyperpolarization in septic shock induced by CLP is likely via non-NO-sensitive GC pathway.  相似文献   

9.
目的总结分析低钾型周期性瘫痪(HOPP)的临床特点。方法回顾分析38例HOPP患者的临床表现及主要辅助检查。结果 38例HOPP患者中有18例由多种诱因诱发,8例为甲状腺功能亢进症,其症状与甲状腺功能无平行关系。HOPP表现为肢体瘫痪,呈对称性,近端重于远端,从下肢发展到上肢。血清钾均降低,22例出现白细胞、中性粒细胞增高,22例有肌酶学变化,以肌酸磷酸激酶(CK)增高为主。口服补钾治疗为主要措施,甲亢性低钾型周期瘫痪须合用抗甲状腺药物及β受体阻滞剂。结论 HOPP发作由多种诱因诱发,部分与甲状腺功能亢进症有关。多数有肌酶学变化,以CK增高明显。  相似文献   

10.
Effects of azumolene on Ca2+ sparks in skeletal muscle fibers   总被引:1,自引:0,他引:1  
Azumolene is an analog of dantrolene, the only approved medicine for treatment of malignant hyperthermia (MH). The pharmacological mechanism of these drugs is to inhibit skeletal muscle sarcoplasmic reticulum (SR) Ca2+ release by modulating the activity of the SR ryanodine receptor (RyR) Ca2+ release channel. To investigate the effects of azumolene on SR Ca2+ channel gating within skeletal muscle fibers, we monitored Ca2+ sparks in permeabilized frog skeletal muscle fibers. Application of 0.0001 to 10 microM azumolene suppressed the frequency of spontaneous Ca2+ sparks in a dose-dependent manner (EC50 = 0.25 microM; Hill coefficient = 1.44), but it did not cause systematic dose-dependent effects on the properties of the Ca2+ sparks. These results suggest that azumolene decreases the likelihood of Ca2+ release channel openings that initiate Ca2+ sparks, thereby decreasing spark frequency, but it has little effect on aggregate Ca2+ channel open times during a spark. To assess azumolene inhibition of RyRs activated in a manner analogous to those activated during an MH episode, we applied DP4, a synthetic peptide corresponding to a central region of RyR1 (Leu2442 to Pro2477), which mimics an MH modification. Azumolene also decreased Ca2+ spark frequency in a dose-dependent manner without altering spark properties in the DP4 MH model. We conclude that azumolene suppresses the opening rate but not the open time of RyR Ca2+ release channels within skeletal fibers.  相似文献   

11.
1. The function of mitochondria, sarcotubular membranes (heavy microsomes), sarcolemma and myofibrils from the hind-leg skeletal muscle of about 60- and 150-day-old normal and myopathic (UM-X7.1) hamsters was examined. 2. The mitochondrial calcium uptake as well as mitochondrial phosphorylation and respiratory rates were lower in 60-day-old myopathic skeletal muscle, unlike 150-day-old myopathic animals, when pyruvate-malate and glutamate-malate were used as substrates. However, mitochondria from 150-day-old myopathic animals showed depressed glutamate-dependent respiratory and phosphorylation rates and succinate-supported initial rate of calcium uptake. 3. The microsomal calcium-uptake, but not calcium-binding, and Ca2+-stimulated adenosine triphosphatase (ATPase) activity of the 150-day-old myopathic skeletal muscle were lower than the control values. Although microsomal calcium-binding, calcium-uptake and ATPase activities of the 60-day-old myopathic muscle were not depressed significantly, the initial rate of calcium uptake was less than the control. 4. The sarcolemmal Ca2+-ATPase, but not Mg2+-ATPase or Na+ +K+-ATPase, activity was higher in 60-day-old myopathic muscle whereas the activities of all these enzymes from 150-day-old myopathic animals were higher than the control. On the other hand, the Na+ +K+-ATPase activities from 60- and 150-day-old myopathic animals were inhibited by ouabain to a lesser extent in comparison with the respective control values. 5. The myofibrillar Ca2+-ATPase and Mg2+-ATPase activities as well as inhibition of Mg2+-ATPase due to Na+ and K+ in myopathic muscle were no different from the control values. 6. The results reported here give further support to the view that different membrane systems of the dystrophic muscle are defective.  相似文献   

12.
Permanent neonatal diabetes (PNDM) is diagnosed in the first three months of life and is a major management problem as patients require lifelong insulin injections. Recently, activating mutations in the KCNJ11 gene which encodes the Kir6.2 subunit of the KATP channels in the pancreatic beta-cells were found to be an important cause of PNDM. The mutated KATP channels do not close in the presence of adenosine triphosphate (ATP) so the beta-cell membrane is hyperpolarized and insulin secretion does not occur. Some patients have DEND syndrome (developmental delay, epilepsy and neonatal diabetes) with the neurological features arising from mutated KATP channels in muscle, nerve and brain. Defining a genetic aetiology has not only given insights into clinical classification and disease mechanism, but has also influenced treatment. Sulphonylureas, by binding the sulphonylurea receptor, can close the KATP channel. This has led to patients who were insulin-dependent being able to discontinue insulin injections and achieve excellent control with sulphonylurea tablets. In this article we discuss the work that established Kir6.2 mutations as a common cause of neonatal diabetes, the clinical features, the underlying mechanism and the impact on patient treatment.  相似文献   

13.
14.
The neonatal disorder persistent hyperinsulinemic hypoglycemia of infancy (PHHI) arises as the result of mutations in the subunits that form the ATP-sensitive potassium (KATP) channel in pancreatic beta cells, leading to insulin hypersecretion. Diazoxide (a specific KATP channel agonist in normal beta cells) and somatostatin (octreotide) are the mainstay of medical treatment for the condition. To investigate the mechanism of action of these agents in PHHI beta cells that lack KATP currents, we applied patch clamp techniques to insulin-secreting cells isolated from seven patients with PHHI. Five patients showed favorable responses to medical therapy, and two were refractory. Our data reveal, in drug-responsive patients, that a novel ion channel is modulated by diazoxide and somatostatin, leading to termination of the spontaneous electrical events that underlie insulin hypersecretion. The drug-resistant patients, both of whom carried a mutation in one of the genes that encode KATP channel subunits, also lacked this novel K+ channel. There were no effects of diazoxide and somatostatin on beta cell function in vitro. These findings elucidate for the first time the mechanisms of action of diazoxide and somatostatin in infants with PHHI in whom KATP channels are absent, and provide a rationale for development of new therapeutic opportunities by K+ channel manipulation in PHHI treatment.  相似文献   

15.
Torsades de pointes (TdP) arrhythmia is a potentially fatal form of ventricular arrhythmia that occurs under conditions where cardiac repolarization is delayed (as indicated by prolonged QT intervals from electrocardiographic recordings). A likely mechanism for QT interval prolongation and TdP arrhythmias is blockade of the rapid component of the cardiac delayed rectifier K+ current (IKr), which is encoded by human ether-a-go-go-related gene (HERG). Over 100 non-cardiovascular drugs have the potential to induce QT interval prolongations in the electrocardiogram (ECG) or TdP arrhythmias. The binding site of most HERG channel blockers is located inside the central cavity of the channel. An evaluation of possible effects on HERG channels during the development of novel drugs is recommended by international guidelines. During cardiac ischaemia activation of ATP-sensitive K+ (KATP) channels contributes to action potential (AP) shortening which is either cardiotoxic by inducing re-entrant ventricular arrhythmias or cardioprotective by inducing energy-sparing effects or ischaemic preconditioning (IPC). KATP channels are formed by an inward-rectifier K+ channel (Kir6.0) and a sulfonylurea receptor (SUR) subunit: Kir6.2 and SUR2A in cardiac myocytes, Kir6.2 and SUR1 in pancreatic beta-cells. Sulfonylureas and glinides stimulate insulin secretion via blockade of the pancreatic beta-cell KATP channel. Clinical studies about cardiotoxic effects of sulfonylureas are contradictory. Sulfonylureas and glinides differ in their selectivity for pancreatic over cardiovascular KATP channels, being either selective (tolbutamide, glibenclamide) or non-selective (repaglinide). The possibility exists that non-selective KATP channel inhibitors might have cardiovascular side effects. Blockers of the pore-forming Kir6.2 subunit are insulin secretagogues and might have cardioprotective or cardiotoxic effects during cardiac ischaemia.  相似文献   

16.
Congenital hyperinsulinism is a condition of dysregulated insulin secretion often caused by inactivating mutations of the ATP-sensitive K+ (KATP) channel in the pancreatic beta cell. Though most disease-causing mutations of the 2 genes encoding KATP subunits, ABCC8 (SUR1) and KCNJ11 (Kir6.2), are recessively inherited, some cases of dominantly inherited inactivating mutations have been reported. To better understand the differences between dominantly and recessively inherited inactivating KATP mutations, we have identified and characterized 16 families with 14 different dominantly inherited KATP mutations, including a total of 33 affected individuals. The 16 probands presented with hypoglycemia at ages from birth to 3.3 years, and 15 of 16 were well controlled on diazoxide, a KATP channel agonist. Of 29 adults with mutations, 14 were asymptomatic. In contrast to a previous report of increased diabetes risk in dominant KATP hyperinsulinism, only 4 of 29 adults had diabetes. Unlike recessive mutations, dominantly inherited KATP mutant subunits trafficked normally to the plasma membrane when expressed in COSm6 cells. Dominant mutations also resulted in different channel-gating defects, as dominant ABCC8 mutations diminished channel responses to magnesium adenosine diphosphate or diazoxide, while dominant KCNJ11 mutations impaired channel opening, even in the absence of nucleotides. These data highlight distinctive features of dominant KATP hyperinsulinism relative to the more common and more severe recessive form, including retention of normal subunit trafficking, impaired channel activity, and a milder hypoglycemia phenotype that may escape detection in infancy and is often responsive to diazoxide medical therapy, without the need for surgical pancreatectomy.  相似文献   

17.
Voltage-dependent Ca++ channels of excitable cell membranes are coupled to drug recognition sites that influence Ca++ channel gating behavior. In cardiac tissue, these sites are themselves regulated by membrane potential, which may explain the apparent dependence of drug effects on Ca++ channel conductance state. Whether a similar relationship pertains in other (e.g., neural) cells is unknown. To examine this issue, we investigated the effect of K+-depolarization on binding of the dihydropyridine Ca++ channel antagonist, (+)-[3H]PN200-110, to intact PC12 cells in culture. Specific (nifedipine-sensitive) binding of 50 pM (+)-[3H]PN200-110 to intact PC12 cells was increased approximately 3-fold by K+-depolarization. Binding was also increased when membrane potential was abolished by treatment with digitonin; elevated [K+] had no additional effect under these conditions. Enhancement of binding by K+-depolarization was reversible upon repolarization and resulted from an increase in binding affinity (decrease in KD from 274 to 55 pM in equilibrium saturation experiments and from 625 to 44 pM in kinetic studies), without an increase in binding site number. These findings are in accord with a modulated receptor model of Ca++ channel function in which affinity for dihydropyridine Ca++ channel antagonists is enhanced by depolarization, and provide evidence that this form of Ca++ channel regulation occurs in neural, as well as muscle, cells.  相似文献   

18.
Falk T  Kilani RK  Yool AJ  Sherman SJ 《Gene therapy》2001,8(18):1372-1379
Modification of K+ currents by exogenous gene expression may lead to therapeutic interventions in skeletal muscle diseases characterized by alterations in electrical excitability. In order to study the specific effects of increasing outward K+ currents, we expressed a modified voltage-dependent K+ channel in primary cultured rat skeletal muscle cells. The rat Kv1.4 channel was expressed as an N-terminal fusion protein containing a bioluminescent marker (green fluorescent protein). Transgene expression was carried out using the helper-dependent herpes simplex 1 amplicon system. Transduced myoballs, identified using fluorescein optics and studied electrophysiologically with single-cell patch clamp, exhibited a greater than two-fold increase in K+ conductance by 20-30 h after infection. This increase in K+ current led to a decrease in membrane resistance and a 10-fold increase in the current threshold for action potential generation. Electrical hyperexcitability induced by the Na+ channel toxin anemone toxin II (1 microM) was effectively counteracted by overexpression of Kv1.4 at 30-32 h after transduction. Thus, virally induced overexpression of a voltage-gated K+ channel in skeletal muscle has a powerful effect in reducing electrical excitability.  相似文献   

19.
Sepsis-associated vasodilation and shock are centrally orchestrated by NO. Nevertheless, inhibition of NO synthesis may not be the target of choice for the treatment of septic shock because it increases morbidity and mortality. Potential other therapeutic targets include soluble guanulate cyclase (sGC) and K+ channels. In this study, we investigated the protective effect of the sGC inhibitor methylene blue (MB) and various K+ channel inhibitors on LPS- and TNF-induced mortality in mice. In TNF-induced shock, the importance of SK channels was underscored by the ability of a single treatment with the small-conductance calcium-activated SK channel inhibitor apamin to provide significant protection. The only other K+ channel inhibitor that can add survival benefit to the apamin treatment was iberiotoxin, stressing the importance of large-conductance calcium-activated BK channels as well. Although MB can protect against TNF-induced shock and mortality, it cannot prevent LPS-induced mortality. Treatment with the nonspecific K+ channel inhibitor tetraethylammonium or with inhibitors specific for adenosine triphosphate (ATP)-sensitive KATP channels (glibenclamide), BK channels (iberiotoxin), or SK channels (apamin) could not protect either. However, when we combined MB treatment with a single dose of apamin and iberiotoxin, mice were completely protected against LPS-induced death for at least 2 days. In conclusion, the protective effect of MB in combination with apamin and iberiotoxin indicates an important role for SK and BK channels, rather than KATP channels, during endotoxemia. Our results point to SK and BK channels as potential targets in septic shock treatment to be modulated preferentially together with sGC.  相似文献   

20.
Shock states are associated with an impaired tissue oxygen supply-demand relationship and perturbations within the microcirculation, leading to global tissue hypoxia, finally resulting in multiple-organ failure or even death. Two of the most frequent causes of shock are acute hemorrhage and sepsis. Although the origin and the pathophysiology of hemorrhagic and septic shock are basically different, the involvement of adenosine triphosphate-sensitive potassium (KATP) channels, as an important regulator of vascular smooth muscles tone, plays a pivotal role under both conditions. Because the excessive activation of vascular KATP channels is a major cause of arterial hypotension and vascular hyporesponsiveness to catecholamines, the pharmacological inhibition of KATP channels may represent a goal-directed therapeutic option to stabilize the hemodynamic situation in shock states. Despite promising results of preclinical studies, the efficacy of this innovative therapeutic approach remains to be confirmed in the clinical setting. The differences in the species, the comorbidity, and the difficulty in determining the exact onset of shock in clinical practice and, thus, any duration-related alterations in vascular responses and KATP channel activation may explain the discrepancy between the results obtained from experimental and clinical studies. Currently, two of the most relevant problems related to effective KATP blockade in shock states are represented by (1) the dose itself (benefit-risk ratio) and (2) the route of administration (oral vs. i.v.). This review article critically elucidates the published in vivo studies on the role of KATP channel inhibition in both described shock forms and discusses the advantages and the potential pitfalls related to the treatment of human shock states.  相似文献   

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