In order to clarify the cause of intracellular ATP dependency on Zn2+ blockade of KATP channels in pancreatic beta cells, we investigated the KATP channel activity during external Zn2+ application using voltage clamp technique. Cultured beta cells were used for patch-clamp experiment. When 3 mM glucose was applied in bath, KATP channel activity was increased transiently by externally applied Zn2+ in the cell-attached mode and was recoverable. The KATP channel activity was, however, consistently increased by Zn2+ application during the 0 mM glucose in bath. Inside-out mode, internally applied Zn2+ elicited no response on the KATP channels. Another divalent cation, Mn2+, didn't have any effect on the KATP channels. Therefore, This effect, so-called external glucose-dependency on Zn2+ blockade of the KATP channels, might be due to intracellular Zn2+ metabolism which induces ATP consumption. This appears to be a mechanism that the Zn2+ blockade of the KATP channels in the pancreatic beta cells depends on the intracellular ATP concentration.
Adenosine Triphosphate* ; Baths ; Glucose ; Insulin-Secreting Cells* ; KATP Channels* ; Metabolism

The ATP-sensitive potassium (K(ATP)) channels which extensively distribute in diverse tissues (e.g. vascular smooth muscle, cardiac cells, and pancreas) are well-established for characteristics like vasodilatation, myocardial protection against ischemia, and insulin secretion. The aim of this review is to get insight into the novel roles of K(ATP) channels in Parkinson's disease (PD), with consideration of the specificities K(ATP) channels in the central nervous system (CNS), such as the control of neuronal excitability, action potential, mitochondrial function and neurotransmitter release.
Humans ; KATP Channels ; drug effects ; physiology ; Mitochondria ; metabolism ; Parkinson Disease ; metabolism ; therapy

AIMTo investigate the action and mechanism of Syn-1A in reversing the activation of K(ATP) channel induced by weak acidic pH.

METHODSThe patches excised from Kir6.2/SUR2A expressing HEK-293 cells were used to establish inside-out configuration. To examine the actions of weak acidic pH in activation of the channel and the reverse action of Syn-1A on it, the inside-out patches were continuously perfused with the solution of pH from 7.4, 7.0, 6.8, 6.5 to 6.0 with or without Syn-1A. In vitro binding was employed to study the influence of different pH to the binding of Syn-1A to SUR2A subunit.

RESULTSSyn-1A blocked pH 6.5, 6.8 and 7.0 induced activation of the channel, and Syn-1A binding to SUR2A were increased by reducing pH from 7.4 to 6.0.

CONCLUSIONSyn-1A would assert some inhibition of the KATP channels, which might temper the fluctuation of acidic pH-induced K(ATP) channel opening that could induce fatal re-entrant arrhythmias.

HEK293 Cells ; Humans ; Hydrogen-Ion Concentration ; KATP Channels ; metabolism ; Patch-Clamp Techniques ; Potassium Channels ; metabolism ; Potassium Channels, Inwardly Rectifying ; metabolism ; Syntaxin 1 ; pharmacology

The effects of acute cooling/rewarming on cardiac K(+) currents and membrane potential were investigated. Membrane potential and current were assessed with whole-cell patch-clamp technique in current- and voltage-clamp modes. When the temperature of bath solution was decreased from 25 °C; to 4 °C, the transient outward current (I(to)) was completely abolished, the sustained outward K(+) current (I(ss)) at +60 mV and the inward rectifier K(+) current (I(K1)) at -120 mV were depressed by (48.5±14.1)% and (35.7±18.2)%, respectively, and the membrane potential became more positive. After the temperature of bath solution was raised from 4 °C; to 36 °C;, the membrane potential exhibited a transient hyperpolarization and then was maintained at a stable level. In some myocytes (36 out of 58), activation of the ATP-sensitive K(+) (K(ATP)) channels after rewarming was observed. The rewarming-induced change in the membrane potential was inhibited by the Na(+)/K(+)-ATPase inhibitor ouabain (100 μmol/L), and the rewarming-elicited activation of K(ATP) channels was inhibited by the protein kinase A inhibitor H-89 (100 μmol/L). Moreover, decrease of the temperature from 25 °C; to 4 °C; did not induce any significant change in cell volume when the cell membrane potential was clamped at 0 mV. However, significant cell shrinkage with spots was observed soon after rewarming-induced activation of K(ATP) channels. These data demonstrate that acute cooling/rewarming has a profound influence on the membrane potential and K(+) currents of ventricular myocytes, and suggest that activation of K(ATP) channels may play a role in cardiac cooling/rewarming injury.
Animals ; Cold Temperature ; Isoquinolines ; pharmacology ; KATP Channels ; metabolism ; Membrane Potentials ; Myocytes, Cardiac ; physiology ; Patch-Clamp Techniques ; Rats ; Rewarming ; Sulfonamides ; pharmacology

Intermittent hypoxia (IH), or periodic hypoxia is referred as exposure to hypoxia interrupted by normoxia that occurs under many physiological and pathophysiological conditions. A lot of researches showed that IH adaptation, like ischemic preconditioning (IPC) and long-term high-altitude hypoxic adaptation (LHA), had significant cardioprotective effects including increasing the tolerance of myocardium to ischemia/reperfusion injury, limiting infarction size and morphologic damage, inhibiting apoptosis of myocardial cells, enhancing recovery of cardiac function in ischemia/reperfusion, and antiarrhythmia. However, the precise mechanisms underlying the protective effects of IH against ischemia/reperfusion injury are far from clear. The potential candidates participating in the protective effects of IH include oxygen transport, energy metabolism, neurohumoral regulation, antioxidase, stress protein, adenosine, ATP-sensitive potassium channel, mitochondrion, calcium control, nitric oxide and protein kinase. The effects of IH are affected by the protocol of hypoxic exposure, age and sex of experimental animals. IH adaptation, for longer lasting time than IPC and lesser side effect than LHA, might have a practical value for using.
Adaptation, Physiological ; Calcium ; Energy Metabolism ; Humans ; Hypoxia ; Ischemic Preconditioning ; KATP Channels ; Myocardium ; Myocytes, Cardiac ; Potassium Channels ; Reperfusion Injury ; physiopathology ; prevention & control

The cardiac electrophysiological effects of hydrogen sulfide (H2S) were examined in guinea pig papillary muscles in vitro using intracellular microelectrode technique. The results obtained were as follows: (1) the duration of action potential (APD) in the normal papillary muscles was decreased by NaHS (H(2)S donor, 50, 100, 200 micromol/L) in a concentration-dependent manner; (2) in partially depolarized papillary muscles, 100 micromol/L NaHS not only reduced APD, but also decreased the amplitude of action potential (APA), overshoot (OS) and maximal velocity of depolarization at phase 0 (V(max)); (3) pretreatment with ATP-sensitive K(+) (K(ATP)) channel blocker glibenclamide (20 micromol/L) partially blocked the effects of NaHS (100 micromol/L); (4) pretreatment with L-type Ca(2+) channel agonist Bay K8644 (0.5 micromol/L) also partially blocked the effects of NaHS (100 micromol/L); (5) pretreatment with Ca(2+)-free Krebs-Henseleit solution containing glibenclamide (20 micromol/L) completely blocked the effects of NaHS (100 micromol/L); (6) APD in the normal papillary muscles was increased by DL-propargylglycine (PPG, an inhibitor of cystathionine gamma-lyase, 200 micromol/L). All these results suggest that the electrophysiological effects of H(2)S on papillary muscles in our study are due to an increase in potassium efflux through the opening of K(ATP) channels and a decrease in calcium influx. Endogenous H(2)S may act as an important regulator in electrophysiological characters in papillary muscles.
Action Potentials ; physiology ; Animals ; Calcium ; metabolism ; Female ; Guinea Pigs ; Hydrogen Sulfide ; pharmacology ; In Vitro Techniques ; KATP Channels ; metabolism ; Male ; Papillary Muscles ; metabolism ; physiology

UNLABELLEDOBJECTIVE To investigate the effect of Guanxinkang (GXK) on ATP-sensitive potassium channel in myocardial cells of rat with ischemic/reperfusion injury and its possible mechanism for cardiac vascular protection and anti-myocardial ischemia.

METHODSWistar rats were established into I/R injured models by 10 min perfusion--30 min no-flow ischemia--45 min reperfusion, and divided into 5 groups: the I/R model group and 4 treatment groups treated respectively with glibenclamide, pinacidil, GXK and GXK+glibenclamide. Rats' heart were isolated for detecting Ca(2+)-Mg(2+)-ATPase, Na(+)-K(+)-ATPase activity in myocardial cells, and the changes of current in ATP-sensive potassium channel (K(ATP)) was recorded by whole patch clamp technique. Data were controlled by those taken from normal rats in a control group.

RESULTSK(ATP) in the GXK treated group were higher than that in the I/R model group; and similar to that in the pinacidil treated group (P > 0.05). As compared with the model group, activities of Ca(2+)-Mg(2+)-ATPase and Na(+)-K(+)-ATPase in the GXK treated group were increased significantly (P < 0.05).

CONCLUSIONGXK shows definite intervention effect on myocardial I/R injury; which is possibly by way of furthering the opening of K(ATP) channel, decreasing Ca2+ influx, and inhibiting Ca2+ overload.

Animals ; Calcium ; metabolism ; Drugs, Chinese Herbal ; pharmacology ; KATP Channels ; drug effects ; Male ; Myocardial Ischemia ; metabolism ; physiopathology ; Myocardial Reperfusion Injury ; prevention & control ; Myocytes, Cardiac ; metabolism ; Rats ; Rats, Wistar

The present study aimed to investigate the protective effect and mechanism of hydrogen sulfide donor NaHS administration against gastric mucosal injury induced by gastric ischemia-reperfusion (GI-R) in rats. GI-R injury was induced by clamping the celiac artery of adult male SD rats for 30 min and followed by reperfusion for 1 h. The rats were randomly divided into sham group, GI-R group, NaHS group, glibenclamide group and pinacidil group. Gastric mucosal damage was analyzed with macroscopic injured area, deep damage was assessed with histopathology scores, and the hydrogen sulfide concentration in plasma was determined by colorimetric method. The results showed that pretreatment of NaHS significantly reduced the injured area and deep damage of the gastric mucosa induced by GI-R. However, NaHS did not significantly alter the levels of hydrogen sulfide in plasma 14 d after NaHS administration. The gastric protective effect of NaHS during reperfusion could be attenuated by glibenclamide, an ATP-sensitive potassium channel (K(ATP)) blocker. However, K(ATP) opener pinacidil inhibited the GI-R-induced injury. These results suggest that exogenous hydrogen sulfide plays a protective role against GI-R injury in rats possibly through modulation of K(ATP) channel opening.
Animals ; Gastric Mucosa ; pathology ; Hydrogen Sulfide ; metabolism ; Ischemic Preconditioning ; methods ; KATP Channels ; metabolism ; physiology ; Male ; Rats ; Rats, Sprague-Dawley ; Reperfusion Injury ; prevention & control ; Stomach ; blood supply ; Sulfides ; pharmacology

AIMThe present study described the effects of iptakalim and pinacidil, which belong to two different chemical structures of potassium channel opener (KCO), on mRNA expression for subunits of ATP-sensitive potassium channel (KATP), including SUR1, SUR2, Kir6.1, and Kir6.2.

METHODSReverse transcription-polymerase chain reaction (RT-PCR) using primers specific for these four subunit genes was performed on total RNA from rat tissues of heart, aortic smooth muscle and tail artery smooth muscle, after iptakalim and pinacidil administration for one week.

RESULTSCompared with the normal control group without drug administration, in heart tissue, iptakalim and pinacidil showed no significant effects on mRNA levels of the four subunits of KATP. In endothelium-free aortic smooth muscle, SUR2 mRNA level was up-regulated significantly in pinacidil group, while no subunits were changed by iptakalim treatment. In endothelium--free tail artery smooth muscle, Kir6.1 and Kir6.2 mRNA levels were reduced significantly in iptakalim group, and SUR2 and Kir6. 1 in pinacidil group.

CONCLUSIONThe gene expression patterns of KATP were different among tissues of heart, large artery and small artery. Iptakalim selectively down-regulated the mRNA levels of Kir6.1 and Kir6.2 in smooth muscle of small arteries, and the regulation effect of iptakalim on KATP was different from that of pinacidil in cardiovascular system.

ATP-Binding Cassette Transporters ; Animals ; Gene Expression ; drug effects ; KATP Channels ; drug effects ; metabolism ; Male ; Muscle, Smooth, Vascular ; drug effects ; metabolism ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo study the effects of iptakalim (Ipt), an ATP-sensitive potassium channel opener, on cardiac remodeling induced by isoproterenol (ISO) in Wistar rats.

METHODSISO was given subcutaneously (85 mg/(kg x d), sc, 7 days) to induce cardiac remodeling in rats. The rats in Ipt treated group were administrated with Ipt 3 mg/kg (po) after ISO injection. After treated with Ipt for 6 weeks, the hemodynamic parameters were tested by an eight channel physiological recorder (RM-6000). Then the heart weight was weighed and the cardiac remodeling index was calculated. HE stain and Masson's stain were employed to perform histological analysis, the hydroxyproline(Hyp) content in cardiac tissue was detected by colorimetric method, radioimmunoassay was used to measure the plasma levels of endothelin-1 (ET-1) and prostacyclin (PGI2).

RESULTSSix weeks after ISO injection, the cardiac functions of model group were damaged markedly compared with those of normal group. The characteristics of ventricular remodeling in model group included that the heart weight index, myocyte cross-sectional area, myocardial fibrosis, and the hydroxyproline content in cardiac tissue were all increased significantly. The plasma level of ET-1 was increased, while the plasma level of PGI2 was decreased significantly. These changes could be reversed by Ipt treatment (3 mg/(kg x d) for 6 weeks).

CONCLUSIONIpt can reverse cardiac remodeling induced by isoproterenol in rats. The endothelial protective effect regulating effects of Ipt on the balance between the ET-1 and PGI2 system may be involved in its mechanisms.

Animals ; Endothelin-1 ; blood ; Hemodynamics ; Hydroxyproline ; metabolism ; Isoproterenol ; pharmacology ; KATP Channels ; drug effects ; Male ; Myocardium ; metabolism ; Propylamines ; pharmacology ; Prostaglandins I ; blood ; Rats ; Rats, Wistar ; Ventricular Remodeling ; drug effects