The effects of KATP channel modulators on counterregulatory responses and cognitive function during acute controlled hypoglycaemia in healthy men: a pilot study.

AIMS: To examine the effects of agents that alter potassium adenosine triphosphate (KATP) channel activity in beta-cells on cognitive function and counterregulatory hormone responses during acute hypoglycaemia, given the physiological similarities between the pancreatic beta-cell and the hypothalamic glucose-sensitive neurones (GSN) and the widespread distribution of sulphonylurea receptors in neuronal cells throughout the brain. METHODS: Ten healthy males were studied on four occasions and in random order underwent three stepped hypoglycaemic (plasma glucose aims: 3.4, 2.8, 2.4 mmol/l) and one euglycaemic (plasma glucose aim: 5 mmol/l) insulin clamps. Prior to each hypoglycaemic study, volunteers received either 10 mg glibenclamide, or 5 mg/kg diazoxide or placebo orally. Cognitive function, symptom scores and counterregulatory hormone responses were measured at each glycaemic level. RESULTS: There was no statistically significant effect of either drug on the symptoms generated or the counterregulatory hormonal response during hypoglycaemia. However, cognitive function was better preserved during hypoglycaemia in the glibenclamide-treated arm, particularly four-choice reaction time which deteriorated at a plasma glucose 2.5 mmol/l compared with 3.0 mmol/l with diazoxide (P = 0.015) and 2.9 mmol/l with placebo (P = 0.114). CONCLUSIONS: Single doses of pharmacological agents which alter membrane KATP channel activity do not affect the counterregulatory response to hypoglycaemia but may modify cognitive function during cerebral glucopenia. The unexpected effects of glibenclamide on cortical function suggest a novel action of sulphonylureas that warrants further investigation.     

钾通道开放剂降低血管平滑肌细胞内游离钙浓度(英文)

目的:研究PCO—Pin,Nic,Lem及RP对VMSC内[Ca~(2 )]_i的改变及其可能机制。方法:VSMC加入Fura-2 AM 2.5μmol·L~(-1)37℃下孵育50min,[Ca~(2 )]_i用荧光分光光度计检测。结果:4种PCO能较弱地抑制K~ 30 mmol·L~(-1)诱导的[Ca~(2 )]_i增加,但明显抑制ATP 0.1mmol·L~(-1)诱导的[Ca~(2 )]_i峰相及持续相增加,且呈剂量依赖性。格列苯脲完全阻断Pin,Lem及RP的作用,只部分抑制Nic的作用。无钙液中先给4种PCO,能显著抑制ATP诱导的[Ca~(2 )]_i峰相增加。结论:4种PCO均抑制ATP诱导的[Ca~(2 )]_i增加,此作用与减少细胞外钙内流及细胞内钙释放有关。     

吡那地尔对体外培养大鼠大脑皮层神经细胞缺氧缺糖损伤的保护作用

目的 :探讨ATP敏感性K+ 通道 (KATP)开放剂吡那地尔 (pinacidil,Pin)对缺氧缺糖再复氧损伤大鼠大脑皮层神经细胞的保护作用。方法 :体外培养大鼠大脑皮层神经细胞 ,细胞培养至 10d ,建立神经细胞缺氧缺糖损伤模型 ,观察Pin及KATP阻断剂格列苯脲对缺氧缺糖不同时间 ,再复氧 2 4h后细胞死亡率、丙二醛 (MDA)含量、超氧化物歧化酶 (SOD)活力的影响。结果 :缺氧缺糖、再复氧后大鼠的神经细胞死亡率均显著升高、MDA生成增多、SOD的活力下降 ,Pin干预后 ,细胞死亡率下降、MDA生成减少、SOD的活力升高 ;格列苯脲能拮抗Pin这种保护作用。结论 :Pin对缺氧缺糖损伤神经细胞具有保护作用 ,并与拮抗氧自由基有关     

Die Kombinationstherapie Insulin/Sulfonylharnstoff in der Langzeittherapie des Typ-II-Diabetes nach „Sekundärversagen“

Summary In type 2 diabetes with secondary failure of sulfonylurea therapy good metabolic control can seldom be achieved by insulin therapy even with high insulin doses. Hyperinsulinemia however is a possible risk factor of cardiovascular disease in type 2 diabetes. Maintaining the effects of sulfonylurea action insulin should be added in as small amounts as possible to avoid hyperinsulinemia and to ameliorate hyperglycemia.16 type 2 diabetics with secondary failure were treated either with insulin alone (group A;n=8) or with 3.5 mg b.i.d glibenclamide plus small amounts of intermediate insulin (group B;n=8) in a randomised order. After the inpatient period outpatient control was performed monthly up to six months, later on four times a year up to two years.Both groups were comparable with regard to age, duration of diabetes, body weight and metabolic control. The daily insulin dose was 14±2 IU after one month and 19±2 IU after two years in group B. In contrast 30±3 IU and 43±5 IU respectively were needed in group A (p<0.001). All patients B were treated with one daily injection, all patients A needed two injections. Resulting in nearly identical metabolic control in group A basal insulin levels exceeded those in group B after two years significantly (28.6±3.7 vs. 18.6±1.6 mcU/ml;p<0.01). Endogenous C-peptide response was suppressed in group A compared to group B after inpatient period and after one month (0.12±0.01 vs. 0.49±0.15 and 0.09±0.04 vs. 0.13±0.08 pmol/ml;p<0.05). The combined therapy of insulin and sulfonylureas demonstrates the benefit of a prolonged sulfonylurea administration in the treatment of type 2 diabetes with secondary failure.As compared to common insulin therapy a small amount of exogenous insulin by one daily injection additionally to glibenclamide shows similar improvement in metabolic control. Hyperinsulinemia as a risk factor of macroangiopathy is markedly reduced in patients treated with combined therapy compared to those with insulin alone.

Herrn Professor Dr. N. Zöllner zum 65. Geburtstag gewidmet     

精制蝮蛇抗栓酶加优降糖治疗Ⅱ型糖尿病临床观察

为使Ⅱ型糖尿病及有关并发症的治疗达到简便、适用和良好的效果 ,该研究采用了精制蝮蛇抗栓酶加优降糖治疗Ⅱ型糖尿病 ,并与优降糖治疗组对照 ,3wk一疗程 ,两组病例各 5 5例。结果治疗组总有效率 87 3% (48/5 5 ) ,对照组总有效率6 7 3% (37/5 5 )。经统计学处理 ,P <0 0 5 ,两组疗效有显著性差异 ,该疗法减少了口服降糖药的用量 ,避免了胰岛素的不良反应 ,有利于有关并发症的改善 ,无明显副作用发生 ,疗效确实。     

The effect of glibenclamide on the production of interstitial adenosine by inhibiting ecto-5′-nucleotidase in rat hearts

1. Adenosine exerts cardioprotective effects on the ischaemic myocardium. The production of adenosine in the ischaemic myocardium is attributed primarily to the enzymatic dephosphorylation of adenosine 5′-monophosphate (AMP) by 5′-nucleotidase. We determined the activity of 5′-nucleotidase in rat hearts. The objective of the study was to determine the effects of ATP-sensitive K⁺ (K_ATP) channel antagonists (glibenclamide and 5-hydroxydecanoate) on the production of adenosine, by use of a flexibly mounted microdialysis technique.
2. Rats were anaesthetized and the microdialysis probe was implanted in the left ventricular myocardium, followed by perfusion with Tyrode solution. The baseline level of dialysate adenosine was 0.51±0.09 μM (n=16). Introduction of AMP (100 μM) through the probe increased the dialysate adenosine markedly to 9.79±0.43 μM (n=12, P<0.001 vs baseline), and this increase was inhibited by the ecto-5′-nucleotidase inhibitor, α,β-methyleneadenosine 5′-diphosphate (100 μM), to 0.76±0.12 μM (n=8). Thus, the dialysate adenosine noted during the perfusion of AMP originated from dephosphorylation of AMP by ecto-5′-nucleotidase, and the dialysate level of adenosine attained reflects the ecto-5′-nucleotidase activity in the tissue in situ.
3. Glibenclamide (0.1–100 μM) decreased the adenosine concentration measured during the perfusion of AMP (100 μM) in a concentration-dependent manner (IC₅₀=10.5 μM). In contrast, 5-hydroxydecanoate (10–100 μM) did not affect the concentrations of dialysate adenosine, measured in the presence of AMP (100 μM). These results suggest that glibenclamide inhibits the activity of endogenous ecto-5′-nucleotidase and decreases the concentration of adenosine in the interstitial space of rat ventricular muscles in situ.

     

Interactions between imidazoline compounds and sulphonylureas in the regulation of insulin secretion

1. Imidazoline α₂-antagonist drugs such as efaroxan have been shown to increase the insulin secretory response to sulphonylureas from rat pancreatic B-cells. We have investigated whether this reflects binding to an islet imidazoline receptor or whether α₂-adrenoceptor antagonism is involved.
2. Administration of (±)-efaroxan or glibenclamide to Wistar rats was associated with a transient increase in plasma insulin. When both drugs were administered together, the resultant increase in insulin levels was much greater than that obtained with either drug alone.
3. Use of the resolved enantiomers of efaroxan revealed that the ability of the compound to enhance the insulin secretory response to glibenclamide resided only in the α₂-selective-(+)-enantiomer; the imidazoline receptor-selective-(−)-enantiomer was ineffective.
4. In vitro, (+)-efaroxan increased the insulin secretory response to glibenclamide in rat freshly isolated and cultured islets of Langerhans, whereas (−)-efaroxan was inactive. By contrast, (+)-efaroxan did not potentiate glucose-induced insulin secretion but (−)-efaroxan induced a marked increase in insulin secretion from islets incubated in the presence of 6 mM glucose.
5. Incubation of rat islets under conditions designed to minimize the extent of α₂-adrenoceptor signalling (by receptor blockade with phenoxybenzamine; receptor down-regulation or treatment with pertussis toxin) abolished the capacity of (+)-and (±)-efaroxan to enhance the insulin secretory response to glibenclamide. However, these manoeuvres did not alter the ability of (±)-efaroxan to potentiate glucose-induced insulin secretion.
6. The results indicate that the enantiomers of efaroxan exert differential effects on insulin secretion which may result from binding to effector sites having opposite stereoselectivity. Binding of (−)-efaroxan (presumably to imidazoline receptors) results in potentiation of glucose-induced insulin secretion, whereas interaction of (+)-efaroxan with a second site leads to selective enhancement of sulphonylurea-induced insulin release.

     

Behaviour of glibenclamide on repeated administration to diabetic patients

Summary Six maturity onset diabetic patients took glibenclamide 5 mg by mouth, every morning 10 min before a standard breakfast. Serum levels of immunoreactive glibenclamide, glucose and immunoreactive insulin were measured repeatedly on the first and 15th days of treatment. Measured glibenclamide blood levels were in close agreement with an analogue computer simulation of data obtained from healthy volunteers: there was no accumulation of drug in the blood, but there was strong evidence for the existence of a slowly equilibrating deep compartment. Considerable insulin release and correction of the breakfast-induced hyperglycaemia were observed immediately after administration of the drug, as well as 5 h later, at lunch time. The clinical significance of blood levels of glibenclamide, as well as the correlation of pharmacokinetics with pharmacodynamics, are discussed in the light of these results.Glossary of symbols IR- immuno-reactive - GLI glibenclamide - IRI immuno-reactive insulin - GLU glucose - AK 1 values obtained with patient AK on the first day of treatment - AK 15 values obtained with patient AK on the 15th day of treatment - b serum level - b_max maximal serum level - t time after dose - t_max time of maximal serum level - G gastro-intestinal system - B central compartment (blood) - T peripheral compartment (tissue) - E excreta - M,N coefficients of the equation of a bi-exponential decay curve - µ, v exponents of the equation of a bi-exponential decay curve - e base of natural logarithms - K_BG K_EB K_TB K_BT first order rate constants (e. g. K_BG means: into B, from G) - K_BG first order rate constants - etc. not corrected for the volume of distribution     

复方盐酸二甲双胍片中格列本脲含量及其均匀度的HPLC测定

建立了测定复方盐酸二甲双胍片中格列本脲含量及其均匀度的HPLC法.采用ODS(150 mm×4.6 mm,5μm)色谱柱,流动相为甲醇-pH3.5磷酸二氢铵溶液(53),流速1 ml/min,检测波长274 nm.格列本脲在0.015～0.36 mg/ml范围内具有良好的线性,平均回收率为99.3%,RSD 0.61%.均匀度符合药典规定.     

钾通道阻滞剂对大鼠支气管平滑肌细胞增殖的影响

目的探讨电压依赖性延迟整流钾通道(K_V)、Ca²⁺激活钾通道(K_Ca)和ATP敏感性钾通道(K_ATP)对大鼠支气管平滑肌细胞(BSMC)增殖的影响。 方法应用免疫细胞化学、MTT微量比色分析法及流式细胞术,观察K_V,K_Ca和K_ATP对培养中大鼠BSMC增殖的影响。结果K_V阻断剂4-氨基吡啶(4-AP)显著促进大鼠BSMC增殖细胞核抗原的表达,提高BSMC吸光度值,使S+G₂M期细胞数显著增多,并显著提高基础状态下BSMC内Ca²⁺浓度,而K_Ca阻断剂四乙铵(TEA)和K_ATP阻断剂格列本脲(Glib)均无此效应。 结论大鼠BSMC K_V活性的抑制,可提高细胞内Ca²⁺浓度,促进细胞的增殖,而K_Ca和K_ATP对BSMC的增殖均无明显影响。