Research Progress on Relationship Between Potassium Channels and Visceral Hypersensitivity / 胃肠病学

Visceral hypersensitivity is one of the pathogenesis of functional gastrointestinal disorders (FGIDs) including irritable bowel syndrome and functional dyspepsia. In recent years, more and more studies have suggested that the occurrence of gastrointestinal hypersensitivity is related to the changes of neuronal plasticity in the intestinal nervous system or afferent pathway, and potassium channels play a crucial role in controlling neuronal excitability. Lots of studies have shown that decreased expressions or activities of voltage-gated potassium channels, calcium-activated potassium channels, and two-pore domain potassium channels in nociceptors can increase the excitability of neurons, increase visceral pain, and participate in the occurrence of FGIDs. This article reviewed the research progress on relationship between potassium channels and visceral hypersensitivity.

Role of calcium-activated potassium channels in neuronal pacemaker activity / 中国药理学与毒理学杂志

Spontaneous rhythmic activity of pacemaker neurons in the central nervous system underlies fundamental neurological processes such as locomotion, cognition and circadian rhythm. Among the wide range of ion channels required for its generation, the Ca2+-activated K+(KCa) channels play a prominent role in maintaining physiologically-relevant frequency and pattern of pacemaker activity. Much of our understanding of the functions of KCa channels in pacemaker neurons have been derived from pharmacological studies using channel modulators, such as iberiotoxin and apamin. Despite the significant advances made, recent studies have painted an increasingly complex picture of the effects of widely used KCa channel modulators on unintended targets that may confound our under?standing of their functions. In this review, we discussed the utility and shortcomings of the KCa channel modulators, and highlighted the significance of these findings, because the KCa channel modulators have been used in early clinical trials to treat disorders ranging from Parkinson disease to alcoholism.

Influence of up-regulated expression of HSP70 on myocardial KCa3.1 in rabbits with atrial fibrillation caused by rapid atrial pacing / 心血管康复医学杂志

Objective:To observe influence of up‐regulated expression of myocardial heat shock protein (HSP) 70 in‐duced by heat stress on myocardial calcium‐activated potassium channel (KCa ) 3.1 expression in rabbits with atrial fibrillation (AF) caused by rapid atrial pacing (RAP) .Methods :A total of 24 New Zealand white rabbits were ran‐domly divided into sham operation group (n=8 ,only implant electrode without pacing ) ,pacing group (n=8 ,right atrium (RA) received RAP at 600 times/min for 6h) and heat stress pacing group (heat stress group ,n=8 ,received heat stress preconditioning ,then the same RAP as pacing group ) .Results:Compared with sham operation group and pacing group ,there were significant up‐regulation of HSP70 mRNA and protein expression in different sites of heart [HSP70 protein ,left atrium (LA):(39.00 ± 3.21) vs .(39.75 ± 2.82) vs .(69.75 ± 3.45) ,RA: (38.38 ± 2.92) vs .(39.50 ± 3.89) vs .(69.00 ± 2.93) ,left atrial appendage (LAA):(37.75 ± 3.28) vs .(39.00 ± 3.89) vs . (68.63 ± 3.23) ,right atrial appendage (RAA): (37.00 ± 3.85) vs .(38.38 ± 3.74) vs .(68.75 ± 2.82)] in heat stress group , P0.05 ;compared with pacing group with down‐regulation of KCa3.1 mRNA and protein expressions ,there were significant up‐regulation of KCa3.1 mRNA and protein expressions in different sites of heart [KCa3.1 protein ,LA:(21.25 ± 1.67) vs .(24.00 ± 2.62) ,RA :(21.13 ± 1.96) vs .(23.75 ± 1.83) ,LAA :(21.00 ± 2.07) vs .(23.75 ± 1.67) ,RAA:(20.88 ± 2.03) vs .(23.50 ± 2.45)] in heat stress group ,P0. 05. Conclusion:Heat stress may induce up‐regulated expression of myocardial HSP 70 of myocardium ,and HSP 70 may inhibit down‐regulation of KCa 3. 1 mR‐NA and protein expressions in rabbits with atrial fibrillation.

Effect of trimebutine maleate on ion channels in colon smooth muscle cell of cold restraint stress induced rats / 中华消化杂志

Objective To investigate the effects of trimebutine maleate (TM) on the expression of large conductance calcium-activated potassium channel (BKCa) and ryanodine receptors (RyR)channels at mRNA and protein level in colonic smooth muscle cell of cold restraint stress(CRS)induced rats.Methods A total of 24 Wistar rats were divided into CRS group,CRS with TM group and control group equally.The rats of CRS group were gavaged with 0.9％NaCl (6 ml/kg) daily; the rats of CRS with TM group were gavaged with 15 g/L TM (6 ml/kg) daily and activity was restricted in wire cage at 4 ℃ for two hours,continuously for five days.The rats of control group were gavaged with 0.9 ％ NaCl (6 ml/kg) once without CRS.The amount and characteristics of stool of rats in each group were observed.The colonic smooth muscle was isolated to detect the expression of BKCa and RyR at mRNA and protein level by reverse transcription-polymerase chain reaction (RT-PCR) and Western Blot.Results The median of rats defecation particles of CRS group was six,control group was one and CRS with TM group was five.Compared with control group,the defecation appearance of CRS group and CRS with TM group was looser and wetter observed by naked eyes.Compared with control group,there was no obvious pathological changes in CRS and CRS with TM group.There was no significant difference in the mRNA expression of BKCa and RyR channels between control group and CRS group.Compared with control group,the BKCa expression at mRNA level of CRS with TM group increased 1.45 fold.Compared with control group,the RyR2 expression at mRNA level of CRS with TM group increased 1.32 fold.Compared with control group,the BKCa expression at protein level of CRS with TM group increased 1.39 fold,and there was no RyR2 expression band at protein level.Conclusion TM might affect colonic smooth muscle contraction through the upregulation of BKCa expression at mRNA and protein level and RyR expression at mRNA level.

Effect of propofol on spontaneous transient outward K+ currents in mouse cerebral arterial smooth muscle cells / 中华麻醉学杂志

Objective To investigate the effects of propofol on the spontaneous transient outward K+ currents in mouse cerebral arterial smooth muscle cells.Methods Kunming mice of both sexes,weighing 18-22 g,were used in this study.Vascular smooth muscle cells were freshly isolated from cerebral arteries in two steps.Five cells were chosen and studied.When holding potential was - 30 mV,spontaneous transient outward K+ currents were recorded before and after the application of 56 μmol/L propofol by perforated whole-cell patch-clamp technique.The amplitude,frequency,area under the curve and half time width of spontaneous transient outward K+ currents were analyzed.Results Propofol 56 μmol/L significantly increased the amplitude,frequency and area under the curve of spontaneous transient outward K+ currents.There was no significant change in the half time width of spontaneous transient outward K+ currents after administration,Conclusion Propofol can activate spontaneous transient outward K+ currents in mouse cerebral arterial smooth muscle cells,and thus induces vascular smooth muscle relaxation.

The effect of cholecystokinin on proximal colon myocyte in guinea-pigs and its mechanism / 中华消化杂志

Objective To investigate the effect of cholecystokinin (CCK) on colon motility and its mechanism in development of irritable bowel syndrome via recording ionic channels currents and contraction of guinea-pig proximal colon. Methods The guinea-pigs (body weight ranged from 200 g to 250 g) were deprived of food, but not water, for 12 hours before experiment. The animal was sacrificed and 6 cm of proximal colon was obtained. The contractile activity of isolated proximal colon in 1 × 10-7 ,5 × 10-7 or 1 × 10-6 mol/L of CCK-8 solution was recorded. The impact of 1 × 10-7 , 5 × 10-7 and 1 × 10-6 mol/L of CCK-8 and 1 × 10-6 mol/L CCK-8 nifidipin on current of calcium activated potassium channel (IBKac) was detected with an EPC-10 amplifier and an image analysis software.Results In comparison with blank [(0. 68 ±0. 12) g], the amplitude of colon contraction in 1 × 10-7 ,5×10-7 and 1×10-6 mol/L of CCK-8 was increased by (15. 0±1.5)%,(28. 0±1.4)%, and (36.0±1.6) %, respectively ( n = 7, P = 0. 023,0. 005 and 0. 01 ), but there was no significant change of frequency. When exogenous stimulation at +60 mV, the current of IBKac was enhanced to (117. 45 ± 3.60)%, (125.42± 5. 30)% or (136. 98±6. 80)% in 10-7 ,5 × 10-7 or 10-6 mol/L of CCK-8,respectively, compared with controls (n= 7, P＜0.01 ). However, after adding nifidipin, the current of IBKca was reduced to (102.23±5.60)% in 10-6mol/L of CCK-8 at +60 mV when compared with controls (n=7, P= 1. 491 ). Conclusion CCK enhances proximal colonic motility by increasing Ca2+ influx and IBKac current, which is characterized by enhancement of amplitude of contraction.

Ca2+-activated K+ Current in Freshly Isolated c-Kit Positive Cells in Guinea-pig Stomach

This study was designed to isolate Ca2+-activated K+ current (IKCa) and elucidate its physiological significance in freshly isolated interstitial cells of Cajal (ICCs) of guinea-pig stomach. Single ICC was freshly isolated by enzymatically dissociating from myenteric border of gastric antrum free of circular muscles, and conventional whole-cell voltage clamp technique including immunohistochemical techniques were employed to characterize the cells: In myenteric border of gastric antrum, ICC-MY (ICCs from myenteric border) were detected by immunohistochemical reactivity, and single ICC-MY which has many branches was immunohistochemically c-Kit positive. Under K+-rich and 0.1 mM ethylene glycol-bis (2-aminoethyl ether)-N,N,N',N'-tetraacetic acid pipette solution, ICC produced spontaneous inward current (-256+/-92.2 pA). When step-depolarizing pulse from -80 to +80 mV was applied at holding potential (Vh) of -80 mV, voltage-dependent outward currents were recorded with superimposed spontaneous transient outward currents (STOCs). Both STOCs and outward currents were reversibly affected by tetraethylammonium chloride (TEA) and iberiotoxin (IbTX); 2 mM TEA and 200 nM IbTX completely abolished STOCs and significantly inhibited outward K+ current over the whole potential range tested for current/voltage (I/V) relationship. In addition, TEA delayed repolarization phase of spontaneous inward current. The present results indicate the presence of IKCa in a single ICC, and it might be involved in regulation of repolarizing phase of spontaneous inward current in guinea-pig stomach.

Role of three kinds of potassium channel in airway hyperresponsiveness of asthmatic guinea pigs / 中国病理生理杂志

AIM: To investigate the role of Ca2+ - activated, delayed - rectifier and ATP sensitive K+ channel (KCa, Kdr, KATP) in airway hyperresponsiveness of asthmatic guinea pigs. METHODS: The method of recording the tone of isolated trachea rings was performed, and the changes of dose-response curves of trachea rings to histamine caused by different K+ channel blockade were investigated. RESULTS: (1) After inhibition of KCa, by tetraethylammonium (TEA) , the dose - response curve of trachea rings to histamine did not change in control group, while the maximal contraction of trachea rings to 10-4 mol/L and 10-3 mol/L histamine decreased significantly ( P

Properties of ACh-sensitive BK channels in mice type Ⅱ vestibular hair cells and its modulation by calcium / 中国病理生理杂志

AIM: To explore the properties of the acetylcholine(ACh)-sensitive potassium channel in type Ⅱ vestibular hair cells(VHCs Ⅱ) in mice saccular macula and the modulation effect of calcium ions.METHODS: Under the whole-cell patch mode,the pharmacology properties of ACh-sensitive potassium channel and the modulation of calcium ions on ACh-sensitive potassium channel were investigated.RESULTS: Following extracellular perfusion of ACh,VHCs Ⅱ displayed a slow and sustained outward current,which was sensitive to tetraethylammonium(TEA,5 mmol/L) and charybdotoxin(CTX,100 nmol/L),but not sensitive to 4-aminopyride(4-AP,15 ?mol/L).ACh-sensitive potassium current was inhibited by intracellular application of ethylene glycol-bis(B-aminoethylether)-N,N,N',N'-tetraacetic-acid(EGTA,5 mmol/L) and extracellular perfusion of Cd2+ and Ni2+,respectively.Intracellular application of heparin(8 g/L) failed to inhibit ACh-sensitive potassium current.CONCLUSION: Extracellular application of ACh activates the big conductance,calcium-dependent potassium current(BK) in VHCs Ⅱ of mice,which is potently modulated by extracellular Ca2+ ions.However,intracellular IP3-dependent Ca2+ ions release mechanism is not involved in the activation of the ACh-sensitive BK channel.

Role of calcium activated potassium channel in cardioprotection induced by anoxic postconditioning in isolated rat heart / 中国病理生理杂志

AIM: To investigate whether calcium activated potassium channel(KCa) and mitochondrial permeability transition pore(mPTP) contribute to cardioprotective effect elicited by anoxic postconditioning.METHODS: The isolated perfused hearts of male Sprague-Dawley rats were subjected to 30 min global anoxic followed by 120 min reoxygenation.Formazan content of myocardium was measured at 490 nm spectrophotometrically,and the level of lactate dehydrogenase(LDH) in the coronary effluent was detected.The absorbance of isolated heart mitochondria at 520 nm was determined.RESULTS: Anoxic postconditioning increased formazan content,reduced LDH release,improved the hemodynamic parameters of the left ventricular developed pressure,maximal rise/fall rate of left ventricular pressure,left ventricular end-diastolic pressure and rate pressure product and attenuated the decrease of coronary flow during reperfusion.Pretreatment with paxilline(1 ?mol/L) inhibited the effect of anoxic postconditioning.The opening of mPTP was suppressed in the mitochondria isolated from A/R hearts treated with anoxic postconditioning.CONCLUSION: The findings indicate that in the isolated rat heart,anoxic postconditioning protects myocardium against anoxic/reoxygenation injury via inhibiting KCa and the mPTP opening.

Effect of remifentanil on calcium-activated potassium currents in human mesenteric arterial smooth muscle cells / 中华麻醉学杂志

Objective To investigate the ionic mechanism of remifentanil-induced vaso-relaxation by recording calcium-activated K~+-currents(IKCa)in human arterial smooth muscle cells(MASMCs).Methods Human MASMCs were obtained freshly by the method of enzymolysis.IKCa were separated with 4-AP 5 mmol?L~(-1) and recorded by the whole-cell voltage-clamped technique.The effects of remifentanil(1.2,4.8,19.4 mmol?L~(-1))on amplitude and threshold of activation for IKCa were assessed.Results Remifentanil significantly increased IKCa and had no effect on the threshold of activation for IKCa as compared with the control group(P＜0.05 or 0.01),and the IKCa returned to the baseline level after remifentanil was washed out.Conclusion Remifentanil produces vasodilation by activating IKCa in MASMCs.

Effects of caffeine and ryanodine on KCa in porcine coronary artery smooth muscle cells / 中国病理生理杂志

AIM:To study the effect of caffeine on the large conductance calcium activated potassium (KCa) channels by patch-clamp technique on smooth muscle cells enzymatically isolated from the porcine coronary artery (PCASMC),and to investigate the effect of ryanodine on KCa being activated by caffeine.METHODS:Using the single channel patch-clamp technique,single PCASMC was isolated by collagenase,the activity of single KCa channel was recorded in porcine coronary artery smooth muscle cells.RESULTS:Caffeine (0.1-10 mmol/L) enhanced the open probability (Po) of KCa channels in a dose-dependent manner in the intracellular side of inside-out patches and its effect was almost completely abolished by washout. Caffeine decreased the mean close time markedly,but had no effect on the amplitude of KCa channels. However,ryanodine (10-40 ?mol/L) decreased Po of KCa channels activated by caffeine in a dose-dependent manner in cell-attached patches. The mean open time also decreased.CONCLUSION:Caffeine directly activates KCa channels of porcine coronary artery smooth muscle cells in inside-out patches,the activity of single KCa channel is inhibited by ryanodine indirectly in cell-attached patches.

Effect of potassium channels on acute hypoxic pulmonary vasoconstriction in COPD and chronic hypoxic patients / 中国病理生理杂志

AIM: The aim of this study is to investigate the possible role of potassium channel in hypoxic pulmonary vasoconstriction (HPV). METHODS: Fresh human lung tissues were obtained from the Division of Chest Surgery to establish a human model of HPV in vitro. Three groups, control group, COPD group and COPD plus chronic hypoxia group were divided. Human isolated pulmonary artery rings and specific blocking agent corresponding to K_V, K_ Ca, K_ ATP were used to investigate the possible role of the potassium channel in HPV. RESULTS: (1) In acute hypoxia, the vascular ring tension in three groups all increased (P