Developmental delay, Epilepsy and Neonatal Diabetes (DEND) syndrome is the most severe form of Permanent Neonatal Diabetes with KCNJ11 gene mutation which accounts for most of the cases. We report the first DEND syndrome in Malaysia with heterozygous missense mutation Q52R at KCNJ11 (Kir6.2) gene with delayed presentation beyond 6 months of age and failure to transition to glibenclamide. This report signifies the phenotypical variability among patients with the same genetic mutation and the different response to treatment.
Glyburide

Background and Objective: Type 2 (T2DM) and gestational diabetes mellitus (GDM) among pregnant Filipinos have been increasing over the years because of lifestyle westernization. While insulin has been the safe mainstay when dietary measures fail to maintain normoglycemia during pregnancy, recent studies have suggested oral hypoglycemic agents (OHAs) such as metformin and glibenclamide, may offer cheaper and efficacious alternatives. The problem however, is the passage of these drugs through the placenta which may pose possible danger towards the development of the growing embryo. The proposed study aims to evaluate and compare the embryotoxic and teratogenic potentials of the varying concentrations of the two PhilHealth covered oral hypoglycemic agents in the Philippines, namely metformin (biguanide) and glibenclamide (sulfonylureas). Methodology: In this study, a comparison on embryotoxic potentials of metformin and glibenclamide was conducted using zebrafish embryotoxicity test (ZFET) across concentrations found in fetal (10, 20, 100, 500, 1000, 2000 μg/L) and maternal serum (10, 20, 100, 500, 1000, 2000 mg/L). Results and Conclusions Results revealed that metformin showed no significant (p>0.05) lethal effects, but revealed significant risk for teratogenicity, specifically decreased head and tail lengths and advanced hatching. Conversely, glibenclamide revealed significant potential for lethal (e.g., coagulation) and teratogenic effects including pericardial and yolk sac edema, spinal deformity and increased tail length. Comparative evaluation between the two OHAs reveal that glibenclamide has significantly (p<0.05) higher lethal and teratogenic effects. Together, our results suggest that the use of metformin over glibenclamide is favorable for safety testing in pregnant women suffering T2DM and GDM for the benefit of expanding treatment options for these diseases.
Glyburide ; Metformin ; Teratogenesis ; Zebrafish

To identify the presence of inwardly rectifying K+ channels and its characteristics, membrane currents were measured using a whole-cell patch clamp from isolated gastric myocytes of guinea-pig. Change of external K+ concentration from 5 to 90 mM induced an inward current at a holding potential of 80 mV. The high K+-induced inward current was blocked by Ba2+ and Cs+, but not by glibenclamide. With 90 mM K+ in bath, the Ba2+- and Cs+-sensitive currents showed strong inward rectification. Ten mM TEA weakly blocked the inward current only at potentials more negative than 50 mV. With 90 mM K+ in bath, hyperpolarizing step pulses from 10 mV induced inward currents, which were inactivated at potentials more negative than 70 mV. Reduction of external K+ to 60 mM decreased the amplitudes of the currents and shifted the reversal potential to more negative potential. The inactivation of inward K+ current at negative clamp voltage was not affected by removing external Na . These results suggest that the inwardly rectifying K+ channels may exist in gastric smooth muscle.
Baths ; Glyburide ; Membranes ; Muscle Cells* ; Muscle, Smooth ; Tea

BACKGROUND: This study was designed to evaluate the role of KATP channel activation and change of monophasic action potential duration on cardioprotective effect of ischemic preconditioning in cat. METHODS: 34 cats were divided into 4 groups: control (n=10), ischemic preconditioning(n=8), glibenclamide pre-treated(n=8) and nicorandil pre-treated group(n=8). Ischemic preconditioning was done in ischemic preconditioning and glibenclamide pre-treated groups by 3 episodes of 5 min ischemia and 10 min reperfusion. All subjects underwent 40 min of ischemia and 40 min reperfusion. The KATP channel antagonist glibenclamide was given as intravenous bolus (0.5mg/kg) 10 min before ischemic precondtioning and infused (5 microgram/min) during ischemic preconditioning. Nicorandil, a KATP channel opener was injected as intravenous bolus (0.5mg/kg) before 40 min ischemic procedure. Monophasic action potential duration at 50% repolarization(MAP50) was measured in the ischemic and non-ischemic area respectively by epicardial probe throughout the experiment. The effects of ischemic preconditioning were determined by infarct size (% area at risk). RESULTS: Ischemic preconditioning or pretreatment with nicorandil prior to 40 min ischemia demonstrated a significant reduction in infarct size(26.6+/-7%, 33+/-8% infarction of the risk zone, respectively, p<0.01, p<0.05 vs. control) with respect to control(42+/-7% infarction of the risk zone). Pretreatment with glibenclamide abolished the effect of ischemic preconditioning(40+/-8% infarction of the risk zone, p=NS vs. control) Ischemic preconditioning group exhibited a significant reduction of ischemic area MAP50 duration in the ischemic area during preconditioning; at first preconditioning 123+/-9msec vs. 137+/-19msec control(p=NS), at second preconditioning 105+/-16msec vs. 140+/-19msec control(p<0.01), at third preconditioning 109+/-15msec vs. 138+/-19msec control(p<0.05). Pretreatment with glibenclamide prevented the reduction of MAP50 in the ischemic area during ischemic preconditioning. During 40 minutes ischemia, MAP50 shortening was more pronounced in the preconditioned group than in control group; at 10 min 85+/-22 msec vs. 131+/-31msec control(p<0.05), at 20 min 88+/-21msec vs. 130+/-32msec control(p<0.05), and at 30 min 103+/-24msec vs. 136+/-30msec control(p<0.05). This shortening effect was prevented by glibenclamide pretreatment. Nicorandil pretreatment pronounced the ischemic shortening of MAP50 in ischemic area and the nicorandil effect was most significant during early ischemic period; at 10 min 97+/-21msec(p<0.05 vs. control), at 20 min 104+/-32msec (p=NS vs. control), and at 30 min 134+/-28msec(p=NS vs. control). MAP50 measured in non-ischemic area was not significantly different between groups. CONCLUSION: We conclude that KATP channel activation and monophasic action potential duration shortening play a important role in myocardial protection during ischemic injury.
Action Potentials* ; Animals ; Cats* ; Glyburide ; Infarction ; Ischemia ; Ischemic Preconditioning* ; Nicorandil ; Reperfusion

BACKGROUND: It is generally accepted that propofol does not inhibit hypoxic pulmonary vasoconstriction (HPV). However, because the previous studies for the effects of propofol on HPV were established in vivo, the effects of physiologic variables could not be ruled out. Therefore, we investigated the effects of various concentrations of propofol on HPV at isolated rat lungs and the relationship of these effects of propofol on HPV and endothelium-derived relaxing factor (EDRF) and an ATP-dependent K+ channel which were candidates as the mechanism of HPV. METHODS: In 30 isolated rat lungs, after three hypoxic challenges for 5 minutes, we administered saline in the control group, N(G)-nitro-L-arginine methyl ester (L-NAME) in the L group and glibenclamide in the G group followed by three hypoxic challenges for 5 minutes. In addition, we studied the effects of various concentrations of propofol on HPV in the three groups. RESULTS: L-NAME and glibenclamide did not alter baseline pulmonary arterial pressure but L-NAME significantly enhanced HPV. Clinical concentrations of propofol did not affect HPV and high concentrations of propofol inhibited HPV. The pretreatment of L-NAME and glibenclamide did not alter the inhibition of HPV even at high concentrations of propofol. CONCLUSIONS: The EDRF and ATP-dependent K+ channel did not largely contribute to baseline pulmonary arterial tone but EDRF might be released and downregulate HPV. Clinical concentrations of propofol did not inhibit HPV but high concentrations of propofol inhibited HPV. In addition, the mechanism of inhibition of HPV at high concentrations of propofol did not relate to the EDRF pathway and ATP-dependent K+ channel.
Animals ; Arterial Pressure ; Endothelium-Dependent Relaxing Factors ; Glyburide* ; Lung* ; NG-Nitroarginine Methyl Ester* ; Propofol* ; Rats* ; Vasoconstriction*

BACKGROUND: This study investigated the effects of the K+ channel opener, pinacidil on hypoxic pulmonary vasoconstriction in isolated perfused rabbit lungs. In order to evaluate the vasodilatation mechanism of K+ channel opener, we also studied the effects of two K+ channel blocker, tetraethylammonium (TEA), a Ca2+ activated K+ channel blocker and glibenclamide (GLB), an ATP-sensitive K+ channel blocker. METHODS: Isolated lungs from white rabbits were ventilated with a normoxic gas (21%O2-5%CO2-74%N2) and a hypoxic gas (3%O2- 5%CO2-92%N2) alternatively, and then perfused with blood-containing perfusate solution. After a hypoxic pressor response (HPR) had been obtained, various drugs were added to the perfusate reservoir to achieve the predetermined circulating concentration, and the influences of the drugs on HPR were then tested. RESULTS: Pinacidil (0.3-6.0 mcM) produced a dose-dependent pulmonary vasodilation on hypoxic ventilation challenge. TEA (1 mM) caused pulmonary vasoconstriction in normoxic ventilation and potentiated a hypoxic pressor response. When the hypoxic pressor response was potentiated by TEA, pinacidil (1.0, 3.0 mcM) reduced the contraction, but GLB did not cause pulmonary vasoconstriction under normoxic ventilation, potentiate a hypoxic pressor response. CONCLUSIONS: Piacidil is capable of opposing the pulmonary responses of acute hypoxia. Moreover the effects of TEA and GLB suggest that HPV might be mediated through Ca2+ activated K+ channels, not through ATP-sensitive K+ channels.
Anoxia ; Glyburide* ; Lung* ; Pinacidil* ; Potassium Channels, Calcium-Activated ; Rabbits ; Tea ; Tetraethylammonium ; Vasoconstriction* ; Vasodilation ; Ventilation

BACKGROUND: It has been generally accepted that Cisapride (Prepulsid?or propulsid?), a widely used gastrointestinal prokinetic agent, is associated with Torsades de Points, a life-threatening arrhythmia. Recently, cisapride-induced APD (action potential duration)-prolongation was inhibited by glibenclamide, a KATP channel blocker. But the direct effect of cisapride on K(ATP) channels has not been studied until now. Therefore, we investigated cisapride's effects on KATP channels of isolated rat ventricular myocytes. METHODS: After the isolation of rat ventricular myocytes, we analysed the single channel current with patch pipettes. The method of analysis was the student t-test. RESULTS: 1) Cisapride (10(-6) M- 10(-4) M) inhibited KATP channel opening without changing channel conductance Ki was about 20micronM, and Hill coefficient was 0.75. 2) Cisapride inhibited pinacidil-induced KATP channel opening in the cell attached mode. CONCLUSIONS: These results suggest that cisapride-induced APD prolongation and arrythmic effects may be partly related to KATP channel inhibition.
Animals ; Arrhythmias, Cardiac ; Cisapride* ; Glyburide ; Humans ; KATP Channels ; Muscle Cells ; Rats

BACKGROUND: K+ channel opener has been considered as a vasorelaxing agent working through hyperpolarization of vascular smooth muscle cells. Renal tubules-proximal, thick ascending limb of Henle and cortical collecting duct-are the site of the diversity of the K+ channel. ATP-sensitive K+ channel has been observed in the apical membranes of the thick ascending limb of Henle and collecting duct, and basolateral membrane of the proximal tubule. It was also shown that K+ channel opener increased renal hemodynamics and elicited diuretic and natriuretic effects. METHODS: To clarify the renal effects of WAY120491, a K+ channel opener, experiments were performed in unanesthetized normotensive and renal hypertensive rabbits allowing unilateral renal arterial infusion of agent. RESULTS: Intrarenal arterial infusion (0.13, 0.32 and 0.64 microgram/kg/min) of WAY120491 increaased CPAH, CCr, urine volume, UNaV, UKV and CH2O. Renal hemodynamic effects and increments of urine volume and free water clearance were completely blocked by glibenclamide (8.2 g/kg/min), while increments of UNaV and FENa were not significantly affected. Renal hemodynamic and tubular effects of WAY120491 were not significantly different in two-kidney one clip Goldblatt hypertensive rabbits from sham-operated rabbits. CONCLUSIONS: These results suggest that WAY120491 elicits renal effects through ATP-sensitive K+ channel in the renal vasculatures and renal tubules and the renal effects of WAT120491 may not be altered in the hypertension.
Diuresis ; Extremities ; Glyburide ; Hemodynamics ; Hypertension ; Membranes ; Muscle, Smooth, Vascular ; Natriuresis ; Natriuretic Agents ; Rabbits* ; Water

OBJECTIVE: The purpose of this study was to investigate the effects of fluoxetine (Prozac) on membrane potential and ionic currents in RINm5F insulinoma cells. METHODS: Membrane potential and ionic currents in RINm5F cell were recorded by using whole-cell and perforated-patch clamp techniques. RESULTS: Under current clamp conditions, diazoxide (200 microM), an activator of K ATP channels, induced a hyperpolarization of the resting membrane potential (-16.1+/-1.4 mV, n=), which was accompanied by a abolition of action potential firing. This diazoxide-induced hyperpolarization was blocked by glibenclamide (10 microM). Fluoxetine produced significant depolarization of membrane potential (15.9+/-3.1 mV, n=) and blocked diazoxide-induced hyperpolarization. Diazoxide activated inward currents in the presence of high external K + (90 mM) at a holding potential of -60 mV. Fluoxetine suppressed diazoxide-activated currents in a concentration-dependent (IC 50 =.84 microM) manner. However, the inhibitory action of fluoxetine was not specific to K ATP currents because it also inhibited both voltage-activated K + and Ca 2+ currents in a concentration-dependent manner. K ATP currents were more sensitive to fluoxetine block than both voltage-activated K + and Ca 2+ currents. CONCLUSION: Our results indicate that fluoxetine increased excitability of RINm5F cells mainly by the preferential block of K ATP currents. Fluoxetine-induced depolarization may influence insulin secretion in insulinoma cells.
Action Potentials ; Adenosine Triphosphate ; Diazoxide ; Fires ; Fluoxetine* ; Glyburide ; Insulin ; Insulinoma* ; Membrane Potentials* ; Membranes*

Ischemic damage is one of the most serious problems. The openers of KATP channel have been suggested to have an effect to limit the ischemic damage. However, it is not yet clear how KATP channels of a cell correspond to hypoxic damage. To address the question, N2a cells were exposed to two different hypoxic conditions as follows: 6 hours hypoxia followed by 3 hours reperfusion and 12 hours hypoxia followed by 3 hours reperfusion. As the results, 6 hours hypoxic treatment increased glibenclamide-sensitive basal KATP current activity (approximately 6.5-fold at 0 mV test potential) when compared with nomoxic condition. In contrast, 12 hours hypoxic treatment induced a relatively smaller change in the KATP current density (2.5-fold at 0 mV test potential). Additionally, in experiments where KATP channels were opened using diazoxide, the hypoxia for 6 hours significantly increased the current density in comparison to control condition (p < 0.001). Interestingly, the augmentation in the KATP current density reduced after exposure to the 12 hours hypoxic condition (p < 0.001). Taken together, these results suggest that KATP channels appear to be recruited more in cells exposed to the 6 hours hypoxic condition and they may play a protective role against hypoxia-reperfusion damage within the time range.
Animals ; Anoxia ; Diazoxide ; Glyburide ; KATP Channels ; Mice* ; Neuroblastoma* ; Potassium Channels* ; Potassium* ; Reperfusion