瑞格列奈引起频发性室性早搏1例

瑞格列奈(诺和龙)为胰岛素分泌刺激药,它通过与胰岛β细胞膜上的特异性受体结合,促进胰岛细胞膜上的ATP依赖性K 通道关闭,抑制K 从β细胞外流,使细胞膜去极化,从而开启电压依赖的Ca2 通道,使细胞外Ca2 进入细胞内,促进胰岛素分泌。而这种刺激胰岛释放的作用是依赖     

格列美脲

[通用名称] glimepiride,格列美脲 [商品名] Amaryl,亚莫利 [化学名称] 1-p-2-3-乙基-甲基-2-氧-3-吡咯啉-1-羧胺基-乙基-苯磺酰基-3-(反式-4-甲基环己基)脲. [药理作用] 本品为第三代磺酰脲类长效抗糖尿病药,其作用机制是通过与胰腺β-细胞表面的磺酰脲受体(相对分子质量为6.5×104的蛋白质)结合,此受体与ATP敏感的K+(KATP)通道相耦连,促使KATP通道关闭,引起细胞膜的去极化,使电压依赖性钙通道开放,Ga2+内流而促使胰岛素的释放,并抑制肝葡萄糖的合成.近期的研究表明,不同的磺酰脲类药物与KATP的亲和力不同.其顺序为:优降糖＝格列美脲>甲苯磺丁脲>氯磺丙脲.此外,格列美脲还可以通过非胰岛素依赖的途径增加心脏葡萄糖的摄取,这可能是葡萄糖转运因子1,4两种蛋白质表达作用增加所致.由于格列美脲对心血管KATP通道的作用弱于格列波脲、格列齐特及格列吡嗪.故心血管的不良反应亦很少.     

磺脲类药物对Kir6．2突变的糖尿病患者更为有效

杂合子可激活KCNJ11的突变,该基因编码ATP敏感性钾通道(KATP)的Kir6.2亚单位,它的突变使30%￣58%的病例在6个月以内就确诊为糖尿病。患者出现酮症酸中毒或严重的高血糖,并接受胰岛素治疗。发病机制是由于B细胞的KATP通道损伤,不能关闭,造成细胞内ATP的升高,胰岛素分泌功能受损,从而引发糖尿病。而磺脲类药物可以通过ATP非依赖途径关闭KATP通道,因此Pearson等人评价了磺脲类药物对Kir6.2突变糖尿病患者的疗效(NEnglJMed,355:467-477.)。在这项研究中,共评价了49例有Kir6.2突变、接受适当剂量磺脲类药物治疗后的血糖水平,并在其…     

Q二甲双胍可否用于肾功能正常但有蛋白尿的患者？可否用于慢性支气管炎、肺心病患者？

二甲双胍不促进胰岛素的分泌，其降糖作用主要通过增加肌肉等组织无氧酵解、减少肠道葡萄糖的吸收、增加外周组织胰岛素的敏感性等途径；二甲双胍几乎全部经尿代谢，所以对肾功能的依赖较大。肾功能正常伴蛋白尿的患者可以根据其尿蛋白水平分为微量蛋白尿和大量蛋白尿阶段，对于前者，     

抗心肌缺血药物的新靶点:线粒体ATP敏感性钾通道

ATP敏感性钾通道 (KATP)是心脏保护作用的调节位点。随着KATP药理学和分子生物学特征的深入研究 ,发现KATP开放剂介导的心脏保护机制并不依赖于动作电位时程(APD)的缩短和负性肌力作用 ,而与线粒体功能有关。细胞内存在线粒体KATP(mitoKATP)。mitoKATP开放的心脏保护作用机制尚不十分清楚 ,可能与K+ 内流 ,线粒体膜去极化 ,降低Ca2 + 超载 ,基质容积增加有关 ,后者可增加ATP合成、促进线粒体呼吸     

Cl~-通道及Ca~(2+)通道阻断剂对ATP触发的牛脑血管平滑肌细胞Ca~(2+)内流作用的影响

采用Fura 2荧光测定胞浆游离Ca2 + 浓度([Ca2 + ]i)变化技术 ,在培养的牛脑中动脉平滑肌细胞上 ,观察电压依赖Ca2 + 通道 (VDCC)抑制药尼莫地平 ,非电压依赖Ca2 + 通道 (NVDCC)SK&F96365以及Cl-通道抑制药呋塞米 ,印防己毒素对ATP引起的[Ca2 + ]i 反应的影响 .实验表明ATP可使 [Ca2 + ]i 呈现双相升高反应 ,即快速峰相及随后持续稳定的平台相 .尼莫地平 ,SK&F96365及印防己毒素对ATP触发的Ca2 + 内流无明显影响 ,而呋塞米能呈浓度依赖性地抑制ATP触发的Ca2 + 内流 .提示ATP触发的牛脑中动脉平滑肌细胞Ca2 + 内流是经SK&F96365不敏感的NVDCC ,与呋塞米敏感的Cl- 通道开放有关 .     

前列腺素F_(2α)增强膜去极化和升高胞内钙促进NIT-1β细胞胰岛素分泌

目的探讨前列腺素F2α(PGF2α)促进NIT-1β细胞葡萄糖刺激性胰岛素分泌的作用机制。方法放射免疫法检测NIT-1β细胞胰岛素分泌量;激光共聚焦显微镜检测细胞[Ca2+]i。结果葡萄糖浓度为16.5mmol·L-1时,PGF2α5μmo·lL-1或钾通道阻断剂四乙胺(TEA)20mmol·L-1均使NIT-1β细胞胰岛素分泌明显增加,而先给予TEA后再加PGF2α或先给PGF2α再加TEA均不能使胰岛素分泌进一步增加。葡萄糖浓度为5.5mmol·L-1时,PGF2α不能使胰岛素分泌增加,预先给予20mmol·L-1TEA再应用PGF2α,胰岛素分泌显著增加。60mmol·L-1KCl和250μmol·L-1二氮嗪使细胞膜处于最大去极化状态时,PGF2α不能促进胰岛素分泌。16.5mmol·L-1葡萄糖浓度下,预先给予氯通道阻断剂4,4′-二异硫氰酸水合茋-2,2′-二磺酸(DIDS),PGF2α不能促进胰岛素分泌。另外,16.5mmol·L-1葡萄糖下,5μmol·L-1PGF2α引起NIT-1β细胞[Ca2+]i升高,而预先给予60mmol·L-1KCl和250μmo·lL-1二氮嗪后再给予PGF2α不能引起细胞[Ca2+]i升高;在DIDS作用下,NIT-1β细胞[Ca2+]i显著降低,恢复静息期后给予PGF2α,细胞[Ca2+]i再次降低。结论促进细胞膜去极化在PGF2α增强胰岛素分泌中起着重要作用。PGF2α可能通过激活氯通道,增强NIT-1β细胞膜去极化,升高细胞[Ca2+]i,促进高浓度葡萄糖刺激下的胰岛素分泌。     

吡那地尔对人肺动脉平滑肌细胞内Ca2+浓度的影响

目的 探讨ATP敏感性钾(KATP)通道开放剂吡那地尔(Pin)对内皮素1(ET-1)诱导的人肺动脉平滑肌细胞(PASMCs)增殖及细胞内[Ca2+]i的影响.方法 体外培养人PASMCs,用ET-1诱导其增殖,应用MTT法、Fluo-3和激光扫描共聚焦显微镜技术评价Pin对ET-1诱导的人PASMCs增殖及PASMCs[Ca2+]i调节的作用.结果 Pin显著抑制ET-1诱导的人PASMCs增殖.呈浓度依赖效应,KATP通道拮抗剂格列本脲呈浓度依赖性阻断Pin的作用;ET-1诱导人PASMCs内[Ca2+]i显著增加,Pin(10 μmol/L)拈抗ET-1诱导的人PASMCs内[Ca2+]i升高.结论 KATP通道开放剂Pin可明显抑制ET-1诱导的人PASMCs增殖作用,抑制细胞内Ca2+浓度增加.     

匹那地尔合用卡立泊来德对离体大鼠心肌梗死范围的影响

<正>三磷酸腺苷(ATP)敏感性钾通道(KATP通道)是受细胞内ATP浓度等多因素调节的钾通道,KATP通道在缺血及再灌注损伤的发生和发展中起很重要的作用。匹那地尔可开放KATP通道,对心脏有保护作用[1]。Na+/H+交换蛋白是一种存在于细胞膜上的糖蛋白,在生理状态下受很多因素的调节[2]。Na+/H+交换阻滞剂卡立泊来德[3]和KATP通道开放剂均可缩小心肌梗     

口服Ⅱ型糖尿病药物的研究

当前,临床使用的口服糖尿病药物主要有4类:磺酰脲类降血糖药;双胍类药物;α—葡萄糖苷酶拮抗剂;最近又开发胰岛素抵抗改善剂。1 作用机制1.1 磺酰脲类(SU) 对 NIDDM 患者而言,其 B细胞内葡萄糖代谢障碍,ATP 合成率低,ATP 感受性钙通道不能完全关闭,对胰岛素分泌造成损害。胰脏 B 细胞膜上还存在 SU 特异受体,与钙通道相关,而与葡萄糖的摄取及代谢无关。SU 药物与 SU受体结合后,ATP 感受性钙通道关闭,而后葡萄糖经过同样的途径使 B 细胞中胰岛素分泌增加。发挥     

Hypoglycemic and hypotriglyceridemic effects of tolbutamide in triphenyltin chloride-induced diabetic rabbits

Triphenyltin (TPT) induces transient hyperglycemia and hypertriglyceridemia in rabbits and hamsters through inhibition of the insulin release stimulated by glucose. The disturbed site in TPT-diabetes is a result of signal transduction occurring before the voltage-dependent Ca2+ channel. The ATP-sensitive K channel (KATP channel) is located immediately at the upstream signal of voltage dependent Ca2+ channels on the signaling pathway of insulin secretion. KATP channel produces depolarization by a signal of ATP through glucose metabolism and by stimulation from sulfonylurea drugs (tolbutamide, glibenclamide). To clarify if the insulin secretion that a KATP channel mediates is inhibited in vivo, we studied the effects of tolbutamide (a sulfonylurea) on changes in plasma glucose, triglyceride and insulin in TPT-diabetic rabbits prepared by po administration of 100 mg TPT-chloride/kg bw. In TPT-diabetic rabbits, plasma glucose decreased to a minimum at about 50% and plasma triglyceride levels also decreased. Insulin release was detected after injecting = 10 mg tolbutamide/kg, and insulin was secreted much higher than in normal rabbits. These findings suggest that the insulin released by tolbutamide stimulus decreased the plasma glucose and triglyceride levels in the TPT-diabetic rabbits. Moreover, a possible mechanism to be considered is as follows: tolbutamide combines with sulfonylurea receptor; membrane depolarization is induced by a KATP channel with the signal of a sulfonylurea receptor; insulin is released. The inhibition of insulin secretion by TPT may be caused by a glucose metabolic disorder in beta cells before the occurrence of membrane depolarization due to closed KATP channels interacting directly with a sulfonylurea receptor.     

Current understanding of K ATP channels in neonatal diseases: focus on insulin secretion disorders

ATP-sensitive potassium (K(ATP)) channels are cell metabolic sensors that couple cell metabolic status to electric activity, thus regulating many cellular functions. In pancreatic beta cells, K(ATP) channels modulate insulin secretion in response to fluctuations in plasma glucose level, and play an important role in glucose homeostasis. Recent studies show that gain-of-function and loss-of-function mutations in K(ATP) channel subunits cause neonatal diabetes mellitus and congenital hyperinsulinism respectively. These findings lead to significant changes in the diagnosis and treatment for neonatal insulin secretion disorders. This review describes the physiological and pathophysiological functions of K(ATP) channels in glucose homeostasis, their specific roles in neonatal diabetes mellitus and congenital hyperinsulinism, as well as future perspectives of K(ATP) channels in neonatal diseases.     

Imidazoline NNC77-0074 stimulates insulin secretion and inhibits glucagon release by control of Ca(2+)-dependent exocytosis in pancreatic alpha- and beta-cells

We have investigated the effects of the novel imidazoline compound (+)-2-(2-(4,5-dihydro-1H-imidazol-2-yl)-thiopene-2-yl-ethyl)-pyridine (NNC77-0074) on stimulus-secretion coupling in isolated pancreatic alpha- and beta-cells. NNC77-0074 stimulated glucose-dependent insulin secretion in intact mouse pancreatic islets. No effect was observed at 相似文献   

Selectivity of prandial glucose regulators: nateglinide, but not repaglinide, accelerates exocytosis in rat pancreatic A-cells

The effects of the two prandial glucose regulators, repaglinide and nateglinide, on ATP-sensitive K(+) (K(ATP)) channel activity, membrane potential and exocytosis in single rat pancreatic A-cells were investigated using the patch-clamp technique. K(ATP) channel activity was reversibly blocked by repaglinide (K(d)=22 nM) and nateglinide (K(d)=410 nM) and this was associated with membrane depolarisation and initiation of electrical activity. The effect of repaglinide and nateglinide on stimulation of glucagon secretion by direct interference with the exocytotic machinery was investigated by the use of capacitance measurements. Nateglinide, but not repaglinide, at concentrations similar to those required to block K(ATP) channels potentiated Ca(2+)-evoked exocytosis 3-fold. In alphaTC1-9 glucagonoma cells addition of nateglinide, but not repaglinide, was associated with stimulation of glucagon secretion. These results indicate that the fast-acting insulin secretagogue nateglinide is glucagonotropic primarily by stimulating Ca(2+)-dependent exocytosis.     

Membrane ion channels and diabetes

Type-2, or non-insulin-dependent diabetes mellitus is a serious disease that is now widespread throughout Western society. Glucose intolerance, or failure of glucose to stimulate insulin secretion, is a primary factor in the manifestation of this disease and is likely to be due to the failure of glucose metabolism to stimulate pancreatic beta-cell electrical activity, calcium influx, and insulin secretion. In this review we describe how ion channels regulate the electrical behaviour of the beta-cell and how the membrane potential depolarises in response to a rise in glucose metabolism. Central to these electrical events is the inhibition of ATP-sensitive potassium channel by ATP, and we summarise recent advances in our understanding of the properties of this ion channel in coupling beta-cell metabolism to electrical activity. We discuss the mechanism, specificity, and clinical implications of the pharmacological inhibition of KATP channels by sulphonyureas and other antidiabetic drugs. The roles of other ion channels in regulating electrical activity are considered, and also their potential use as targets for drug action in treating beta-cell disorders.     

Lack of effect of the vasodilator pinacidil on insulin secretion in healthy humans

Pinacidil is a new antihypertensive vasodilator drug which is supposed to act by opening of ATP-sensitive and glibenclamide-sensitive K+ channels in vascular smooth muscle cell membranes. Similar K+ channels play an important role in insulin secretion from pancreatic islets cells. Inhibition of insulin secretion has been demonstrated with high concentrations of pinacidil in vitro. In the present study the insulin response to oral glucose were studied in six healthy subjects before and on the last day of 2 weeks treatment with pinacidil. The drug was given by the oral route 12.5 mg bid in the first week and 25 mg bid in the second. There were no significant changes in fasting blood levels of insulin or glucose, glucose-stimulated insulin secretion, or oral glucose tolerance during pinacidil administration. These results may suggest that pinacidil at therapeutic concentrations does not activate insulin regulating K+ channels in pancreatic islet cells.     

Resveratrol enhances insulin secretion by blocking K(ATP) and K(V) channels of beta cells

The present study investigated the effect of resveratrol on the electrophysiology and insulin secretion of pancreatic beta cells, and examined resveratrol-induced alterations in insulin levels and plasma glucose of normal and streptozotocin-induced diabetic rats. Whole-cell voltage clamp study in the MIN6 cell, a mouse beta cell line, revealed that resveratrol significantly inhibited ATP-sensitive K(+) current at 3 micromol/l, and voltage-gated K(+) currents at 30 micromol/l. Ca(2+)-activated K(+) current was activated by resveratrol at 100 micromol/l. In MIN6 cells stained with membrane potential dye DiBAC(4)(5), resveratrol markedly depolarized membrane potential at the concentrations of 3-100 micromol/l. Insulin secretion was increased in the presence of resveratrol in MIN6, Hit-T15, and RIN-m5F cells. Resveratrol (3 mg/kg, i.p.) increased insulin secretion associated with a lowering in plasma glucose in normal rats, but not in streptozotocin-diabetic rats within the initial 60 min. In conclusion, resveratrol can act as an insulin-secretagogue through I(KATP) and I(KV) inhibition which can contribute to plasma glucose lowering effect in normal rats.     

Stimulation of insulin secretion by glucose in the absence of diminished potassium (86Rb+) permeability.

Two inhibitors of the nucleotide-sensitive K+ (KATP) channel, tolbutamide and quinine, were utilized in order to assess the role of this channel in glucose-stimulated insulin release from perifused rat islets. In the absence of these drugs, the addition of 15 mM glucose elicited a marked biphasic stimulation of insulin secretion concomitant with a reduction in the rate of 86Rb+ efflux. In the presence of either 500 microM tolbutamide or 100 microM quinine, a reduced rate of efflux of 86Rb+ was observed together with an elevated rate of insulin release. Under such conditions, the addition of 15 mM glucose retained the ability to stimulate insulin secretion though this was associated with a marked increase in 86Rb+ efflux. It is concluded that a net reduction in beta-cell K+ permeability is not an obligatory step in glucose-stimulated insulin release. Thus, glucose is likely to exert depolarizing actions on the beta-cell in addition to the closure of K+ channels.     

咪达唑仑对大鼠单一心室肌细胞ATP敏感性钾电流的作用

目的研究咪达唑仑对大鼠单一心室肌细胞ATP敏感性钾电流(IKATP)的作用。方法急性酶解法分离大鼠心室肌细胞,利用膜片钳制技术全细胞记录法,设保持电位为-40mV,指令电位为-100～+40mV,步阶脉冲20mV,波宽200ms,刺激间隔6s的方波钳制方案进行刺激。结果咪达唑仑能够开放心室肌细胞ATP敏感性钾(KATP)通道,在一定范围内具有剂量依赖性关系。指令电位在-60mV时,咪达唑仑(0.3～10μmol/L)可使KATP通道开放率分别增加至给药前的(119±5)%,(121±4)%和(121±6)%(P<0.01,n=9)。更高浓度(50～100μmol/L)咪达唑仑使KATP通道开放率略有下降,其他指令电位下的IKATP改变也符合此趋势。结论咪达唑仑对大鼠单一心室肌细胞KATP通道具有开放作用,这可能是其发挥心脏保护的机制之一。     

Inhibition of voltage-gated Ca2+ channels and insulin secretion in HIT cells by the Ca2+/calmodulin-dependent protein kinase II inhibitor KN-62: comparison with antagonists of calmodulin and L-type Ca2+ channels.

To probe for the involvement of Ca2+/calmodulin-dependent protein kinase II in the regulation of insulin secretion, the effects of a specific inhibitor of this enzyme, KN-62, on secretagogue-stimulated insulin secretion, cytosolic Ca2+ concentration ([Ca2+]i) rise, membrane depolarization, and nutrient metabolism were examined in HIT-T15 cells. KN-62 dose-dependently inhibited insulin secretion induced by a nutrient mixture (10 mM glucose, 5 mM leucine, and 5 mM glutamine) alone or combined with either the Ca(2+)-mobilizing receptor agonist bombesin or the cAMP-raising agent forskolin in intact cells. KN-62 did not affect Ca(2+)- or GTP analogue-induced insulin secretion from permeabilized cells, indicating an action at a step before exocytosis. The stimulating effects of nutrients on insulin secretion, [Ca2+]i, and membrane depolarization were potentiated by bombesin. Similarly, bombesin promoted a larger depolarization and [Ca2+]i rise in the presence of nutrients. This was associated with enhanced Ca2+ mobilization and the appearance of sustained [Ca2+]i elevation. The bombesin-induced membrane depolarization, like the nutrient effect, was inhibited by diazoxide, suggesting that this is due to closure of ATP-sensitive K+ channels. Bombesin elicited Ca2+ influx by both membrane potential-sensitive and -insensitive conductance pathways. KN-62 did not affect Ca2+ mobilization and only partially reduced Ca2+ entry during the sustained [Ca2+]i rise in bombesin-stimulated cells. When added before or during the stimulation, KN-62 dose-dependently inhibited nutrient- and KCl-stimulated [Ca2+]i elevation and Mn2+ influx (reflecting Ca2+ entry). The calmodulin antagonist CGS 9343B and the L-type Ca2+ channel blocker SR-7037 mimicked the inhibitory effect of KN-62 on stimulated insulin secretion and [Ca2+]i elevation. Membrane depolarization and nutrient metabolism (reduction of a tetrazolium derivative), however, were not altered by KN-62 treatment, indicating that the early coupling events from nutrient metabolism to closure of ATP-sensitive K+ channels remain operative. These results suggest that KN-62 and the calmodulin antagonist CGS 9343B inhibit Ca2+ influx by means of direct interaction with L-type Ca2+ channels, which, in turn, causes inhibition of stimulated insulin secretion. Thus, it appears that Ca2+/calmodulin-dependent protein kinase II is not involved in the regulation of insulin secretion.