A 3D-QSAR Study on a Novel Chromanol Class of I_ (Ks) Potassium Channel Blockers

Aim and Method A novel three-dimensional quantitative structure-activityrelationship (3D-QSAR) method, self-organizing molecular field analysis (SOMFA) , was used toinvestigate the correlation between the molecular properties and a class of chromanol analogs asI_(Ks) blockers. Results The cross-validated correlation coefficient q^2 values (0.698) and noncross-validated correlation coefficient r^2 values (0.701) proved a good conventional statisticalcorrelation. Conclusion The final SOMFA model has therefore good predictive activity for the furthermolecular design of chromanol I_(Ks) potassium channel blockers.

Treatment of Helicobacter pylori with potassium competitive acid blockers:A systematic review and meta-analysis

BACKGROUND Helicobacter pylori(H.pylori)infects over half the global population,causing gastrointestinal diseases like dyspepsia,gastritis,duodenitis,peptic ulcers,GMALT lymphoma,and gastric adenocarcinoma.Eradicating H.pylori is crucial for treating and preventing these conditions.While conventional proton pump inhibitor(PPI)-based triple therapy is effective,there’s growing interest in longer acid suppression therapies.Potassium competitive acid blocker(P-CAB)triple and dual therapy are new regimens for H.pylori eradication.Initially used in Asian populations,vonoprazan(VPZ)has been recently Food and Drug Administration-approved for H.pylori eradication.AIM To assess the efficacy of regimens containing P-CABs in eradicating H.pylori infection.METHODS This study,following PRISMA 2020 guidelines,conducted a systematic review and meta-analysis by searching MEDLINE and Scopus libraries for randomized clinical trials(RCTs)or observational studies with the following command:[("Helicobacter pylori"OR"H pylori")AND("Treatment"OR"Therapy"OR"Eradication")AND("Vonaprazan"OR"Potassium-Competitive Acid Blocker"OR"P-CAB"OR"PCAB"OR"Revaprazan"OR"Linaprazan"OR"Soraprazan"OR"Tegoprazan")].Studies comparing the efficacy of P-CABs-based treatment to classical PPIs in eradicating H.pylori were included.Exclusion criteria included case reports,case series,unpublished trials,or conference abstracts.Data variables encompassed age,diagnosis method,sample sizes,study duration,intervention and control,and H.pylori eradication method were gathered by two independent reviewers.Meta-analysis was performed in R software,and forest plots were generated.RESULTS A total of 256 references were initially retrieved through the search command.Ultimately,fifteen studies(7 RCTs,7 retrospective observational studies,and 1 comparative unique study)were included,comparing P-CAB triple therapy to PPI triple therapy.The intention-to-treat analysis involved 8049 patients,with 4471 in the P-CAB intervention group and 3578 in the PPI control group across these studies.The analysis revealed a significant difference in H.pylori eradication between VPZ triple therapy and PPI triple therapy in both RCTs and observational studies[risk ratio(RR)=1.17,95%confidence interval(CI):1.11-1.22,P<0.0001]and(RR=1.13,95%CI:1.09-1.17,P<0.0001],respectively.However,no significant difference was found between tegoprazan(TPZ)triple therapy and PPI triple therapy in both RCTs and observational studies(RR=1.04,95%CI:0.93-1.16,P=0.5)and(RR=1.03,95%CI:0.97-1.10,P=0.3),respectively.CONCLUSION VPZ-based triple therapy outperformed conventional PPI-based triple therapy in eradicating H.pylori,positioning it as a highly effective first-line regimen.Additionally,TPZ-based triple therapy was non-inferior to classical PPI triple therapy.

Effects Of ATP Sensitive potassium channel opener on the mRNA and pro- tein expressions of caspase-12 after cerebral ischemia-reperfusion in rats

Objective To investigate effects of K_ATP opener on the expressions of caspase-12 mRNA and protein, and to explore the role of endoplasmic reticulum （ER） stress pathway in the mechanism of K_ATP opener protecting against neuronal apoptosis after cerebral ischemia-reperfusion. Methods Two hundred rats were randomly divided into four groups： sham operation group, ischemia-reperfusion group, K_ATP opener group, and K_ATP blocker group. The middle cerebral artery occlusion （MCAO） model was established by intraluminal suture occlusion method; neuronal apoptosis was detected by TUNEL staining. The mRNA and protein expressions of caspase-12 were detected by semi-quantitative RT-PCR and immunohisto-chemical staining, respectively. Results In ischemia-reperfusion group, K_ATP opener group and K_ATP blocker group, the number of apoptotic cells and the mRNA and protein expressions of caspase-12 gradually increased following cerebral reperfusion, and reached the peak at 24 h. In K_ATP opener group, The number of apoptotic cells was significantly less than that in ischemia-reperfusion group and K_ATP blocker group at 12 h, 24 h, 48 h and 72 h （P 〈 0.05 or P 〈 0.01）; while the mRNA and protein levels of caspase-12 were significantly less than those in ischemia-reperfusion group and K_ATP blocker group at all times （P 〈 0.05 or P〈0.01）. There were no differences between the ischemia-reperfusion group and K_ATP blocker group at each time （P〉 0.05）. Conclusion K_ATP opener may protect neurons from apoptosis following the cerebral ischemia-reperfusion by inhibiting ER stress pathway.

Aberrant expression of ether à go-go potassium channel in colorectal cancer patients and cell lines

AIM: To study the expression of ether à go-go (Eag1) potassium channel in colorectal cancer and the relation- ship between their expression and clinico-pathological features. METHODS: The expression levels of Eag1 protein were determined in 76 cancer tissues with paired non- cancerous matched tissues as well as 9 colorectal adenoma tissues by immunohistochemistry. Eag1 mRNA expression was detected in 13 colorectal cancer tissues with paired non-cancerous matched tissues and 4 colorectal adenoma tissues as well as two colorectal cancer cell lines (LoVo and HT-29) by reverse transcription PCR. RESULTS: The frequency of positive expression of Eag1 protein was 76.3% (58/76) and Eag1 mRNA was 76.9% (10/13) in colorectal cancer tissue. Expression level of Eag1 protein was dependent on the tumor size, lymphatic node metastasis, other organ metastases and Dukes’ stage (P < 0.05), while not dependent on age, sex, site and degree of differentiation. Eag1 protein and mRNA were negative in normal colorectal tissue, and absolutely negative in colorectal adenomas except that one case was positively stained for Eag1 protein. CONCLUSION: Eag1 protein and mRNA are aberrantly expressed in colorectal cancer and occasionally expressed in colorectal adenoma. The high frequency of expression of Eag1 in tumors and the restriction of normal expression to the brain suggest the potential of this protein for diagnostic, prognostic and therapeutic purposes.

ATP-sensitive potassium channels:novel potential roles in Parkinson's disease

The ATP-sensitive potassium（KATP）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 KATPchannels in Parkinson＇s disease（PD）,with consideration of the specificities KATPchannels in the central nervous system（CNS）, such as the control of neuronal excitability,action potential,mitochondrial function and neurotransmitter release.

Migration-associated secretion of melanoma inhibitory activity at the cell rear is supported by KCa3.1 potassium channels

Malignant melanoma, characterized by invasive local growth and early formation of metastases, is the most aggressive type of skin cancer. Melanoma inhibitory activity （MIA）, secreted by malignant melanoma cells, interacts with the cell adhesion receptors, integrins a4131 and 05131, facilitating cell detachment and promoting formation of me- tastases. In the present study, we demonstrate that MIA secretion is confined to the rear end of migrating cells, while in non-migrating cells MIA accumulates in the actin cortex. MIA protein takes a conventional secretory pathway including coat protein complex I （COPI）- and coat protein complex II （COPII）-dependent protein transport to the cell periphery, where its final release depends on intracellular Ca2＋ ions. Interestingly, the Ca2＋-activated K＋-channel, subfamily N, member 4 （KCa3.1）, known to be active at the rear end of migrating cells, was found to support MIA secretion. Secretion was diminished by the specific KCa3.1 channel inhibitor TRAM-34 and by expression of dominant- negative mutants of the channel. In summary, we have elucidated the migration-associated transport of MIA protein to the cell rear and also disclosed a new mechanism by which KCa3.1 potassium channels promote cell migration.

Effects of Ginkgo biloba extracts with mirodenafil on the relaxation of corpus cavernosal smooth muscle and the potassium channel activity of corporal smooth muscle cells

In this study, we investigated the effects of a combination of Ginkgo biloba extracts （GBE） and phosphodiesterase type 5 （PDE-5） inhibitors on the muscular tone of the corpus cavernosum and potassium channel activity of corporal smooth muscle cells. Strips of corpus cavernosum from male New Zealand white rabbits were mounted in organ baths for isometric tension studies. After contraction with 1 × 10^-5 mol I^-1 norepinephrine, GBE （0.01-1 mg ml^-1） and mirodenafil （0.01-100 nmol I^-1） were added together into the organ bath. In electrophysiological studies, whole-cell currents were recorded by the conventional patch-clamp technique in cultured smooth muscle cells of the human corpus cavernosum. The corpus cavemosum was relaxed in response to GBE in a dose-dependent manner （from 0.64%±8.35% at 0.01 mg ml^-1 to 52.28%±11.42% at 1 mg ml^-1）. After pre-treatment with 0.03 mg ml^-1 of GBE, the relaxant effects of mirodenafil were increased at all concentrations, After tetraethylammonium （TEA） （1 mmol I^-1） administration, the increased effects were inhibited （P〈0.01）. Extracellular administration of GBE increased the whole-cell K^＋ outward currents in a dose-dependent fashion. The increase of the outward current was inhibited by I mmol 1-1 TEA. These results suggest that GBE could increase the relaxant potency of mirodenafil even at a minimally effective dose. The K＋ flow through potassium channels might be one of the mechanisms involved in this synergistic relaxation.

Changes of Expression of Stretch-activated Potassium Channel TREK-1 mRNA and Protein in Hypertrophic Myocardium

The expression of stretch activated potassium channel TREK-1 mRNA and protein of hypertrophic myocardium was measured. Using a model of hypertrophy induced by coarctation of abdominal aorta in male Wistar rats, the expression of TREK-1 mRNA and protein was detected by using semi quantitative RT-PCR and Western blot respectively. At 4th and 8th week after constriction of the abdominal aorta , rats developed significant left ventricular hypertrophy. As compared to sham-operated group, stretch-activated potassium channel TREK-1 mRNA was strongly expressed and protein was up regulated in operation groups （P〈0.05）. It was concluded that the expression of TREK-1 was up-regulated in hypertrophic myocardium induced by chronic pressure overload in Wistar rats.

Astrocytic Kir4.1 potassium channels as a novel therapeutic target for epilepsy and mood disorders

Astrocytic Kir4.1 channels and spatial potassium buffering：Astrocytes play a crucial role in maintaining the structural and functional integrity of the brain,which includes formation of the blood-brain barrier,maintenance of water and ion homeostasis,metabolism of neurotransmitters and secretion of various neuroactive molecules.

Adenosine triphosphate-sensitive potassium channel opener protects PC12 cells against hypoxia-induced apoptosis through PI3K/Akt and Bcl-2 signaling pathways

Although previous studies have shown the neuroprotective effects of the adenosine triphosphate （ATP）-sensitive potassium （KATP） channel opener against ischemic neuronal damage, little is known about the mechanisms involved. Phosphatidylinositol-3 kinase （PI3K）/v-akt murine thy-moma viral oncogene homolog （Akt） and Bcl-2 are thought to be important factors that mediate neuroprotection. The present study investigated the effects of KATP openers on hypoxia-induced PC12 cell apoptosis, as well as mRNA and protein expression of Akt and Bcl-2. Results demon-strated that pretreatment of PC12 cells with pinacidil, a KATP opener, resulted in decreased PC12 cell apoptosis following hypoxia, as detected by Annexin-V fluorescein isothiocyanate/ propidium iodide double staining flow cytometry. In addition, mRNA and protein expression of phosphorylated Akt （p-Akt） and Bcl-2 increased, as detected by immunofluorescence, Western blot analysis, and reverse-transcription polymerase chain reaction. The protective effect of this preconditioning was attenuated by glipizide, a selective KATP blocker. These results demonstrate for the first time that the protective mechanisms of KATP openers on PC12 cell apoptosis following hypoxia could result from activation of the PI3K/Akt signaling pathway, which further activates expression of the downstream Bcl-2 gene.

Chlorogenic acid alters the voltage-gated potassium channel currents of trigeminal ganglion neurons

Chlorogenic acid（5-caffeoylquinic acid, CGA） is a phenolic compound that is found ubiquitously in plants, fruits and vegetables and is formed via the esterification of caffeic acid and quinic acid. In addition to its notable biological functions against cardiovascular diseases, type-2 diabetes and inflammatory conditions, CGA was recently hypothesized to be an alternative for the treatment of neurological diseases such as Alzheimer＇s disease and neuropathic pain disorders. However, its mechanism of action is unclear.Voltage-gated potassium channel（Kv） is a crucial factor in the electro-physiological processes of sensory neurons. Kv has also been identified as a potential therapeutic target for inflammation and neuropathic pain disorders. In this study, we analysed the effects of CGA on the two main subtypes of Kv in trigeminal ganglion neurons, namely, the IK,Aand IK,Vchannels. Trigeminal ganglion（TRG）neurons were acutely disassociated from the rat TRG, and two different doses of CGA（0.2 and 1 mmol·L21） were applied to the cells.Whole-cell patch-clamp recordings were performed to observe alterations in the activation and inactivation properties of the IK,Aand IK,Vchannels. The results demonstrated that 0.2 mmol·L21CGA decreased the peak current density of IK,A. Both 0.2 mmol·L21and1 mmol·L21CGA also caused a significant reduction in the activation and inactivation thresholds of IK,Aand IK,V. CGA exhibited a strong effect on the activation and inactivation velocities of IK,Aand IK,V. These findings provide novel evidence explaining the biological effects of CGA, especially regarding its neurological effects.

Characteristics of Transient Outward Potassium Channel Exposed to 3 mT Static Magnetic Field

Acutely isolated mouse hippocampal CA3 pyramidal neurons were exposed to 3 mT static magnetic field,and the characteristics of transient outward K+ channel were studied using the whole-cell patch-clamp technique.The experiment revealed that the amplitude of transient outward potassium channel current was reduced.The maximum activated current densities of control group and exposure group were 163.62±20.68 pA/pF and 98.74±16.57 pA/pF(n=12,P<0.01) respectively.The static magnetic field exposure affected the activation and inactivation process of transient outward potassium channel current.Due to the magnetic field exposure,the half-activation voltage of the activation curves changed from 5.59±1.96 mV to 27.87±7.24 mV(n=12,P<0.05) ,and the slope factor changed from 19.43±2.11 mV to 25.87±4.22 mV(n=12,P<0.05) .The half-inactivation voltage of the inactivation curves also changed from-56.09±0.89 mV to-57.16±1.10 mV(n=12,P>0.05) and the slope factor of the inactivation curves from 8.69±0.80 mV to 10.87±1.02 mV(n=12,P<0.05) .The results show that the static magnetic field can change the characteristics of transient outward K+ channel,and affect the physiological functions of neurons.

THE PROTECTIVE EFFECT OF Na^+ CHANNEL BLOCKERS AGAINST CELL DAMAGE CAUSED BY ISCHEMIA

In order to observe it blockers of sodium channel obsesses the neuroprotective effect on hippocampal CA 1 pyramidal cell under the condition of transient brain ischemia, the present experiment used 24 male Wistar rats aged 9 months and divided them into four groups. Lidocaine and/or furosemide were injected introcerebroventicularlly (I.C.V). Stained with H E and accounted the CA 1 pyramidal cell numbers by computer in each group suggested following findings: Although 5 μl of 2% lidocaine was injected I.C.V, the results indicated lidocaine didn't have any blockade to pyramidal cell injuries in hippocampal CA 1 area (P<0 05). In the group medicated with 2 5μl of both 2% lidocaine and 2% furosemide, the results showed that the combined approach had a blockade to injuries of pyramidal cells compared with control group (P<0 01). The present experiment indicates that the combined blockade of lidocaine and furosemide injected I.C.V. to Na + channel can prevent the injuries from hippocampal neurons owing to ischemia.

Effect of acupuncture combined with Xijing Tongmai decoction on the sustained expression of transient outward potassium channel related protein in rats with myocardial infarction

Objective:To observe the sustained expression of transient outward potassium channel related proteins at the end of the treatment and 30 days after the end of the treatment in rats,and to explore the sustained curative effect and mechanism of acupuncture combined with Xijingtongmai decoction in rats with myocardial infarction.Methods:Twenty of 130 male SD rats were random extracted as the control group,and the rest were used to establish myocardial infarction by fed with high-fat diet and then injected with isoproterenol.According to ECG,80 rats were successfully established.Then they were randomly divided into model group,acupuncture combined with Chinese medicine group,acupuncture group and Western medicine group.The content of bFGF protein was measured by ELISA.The protein contents of Kv1.4,Kv4.2,Kv4.3 and KChIP2 were measured by Western blot.Results:At the end of treatment,compared with the model group,the protein contents of Kv1.4,Kv4.2,Kv4.3,KChIP2 and bFGF in each treatment group increased,and the increase was most significant in the acupuncture combined with Chinese medicine group(P<0.05).At the end of treatment,compared with the model group,the protein contents of Kv1.4,Kv4.2,Kv4.3,KChIP2 and bFGF in each treatment group increased,and the increase was most significant in the acupuncture combined with Chinese medicine group(P<0.05).Compared with the treatment group at the end of treatment,the expression of Kv1.4,Kv4.2,Kv4.3,KChIP2 and bFGF protein in each treatment group 30 days after the end of treatment decreased slightly(P<0.05),but still higher than that of the model group at this time(P<0.05).The combination of acupuncture and Chinese medicine group decreased the least of them(P<0.05).Conclusion:The results showed that acupuncture combined with xijingtongmai decoction had a sustained good effect.Its sustained action mechanism may be achieved by continuously increasing the protein content of Kv1.4,Kv4.2,Kv4.3,KChIP2 and bFGF through transient outward potassium channel.

Acetylcholine modulates transient outward potassium channel in acutely isolated cerebral cortical neurons of rats

BACKGROUND： The neuronal transient outward potassium channel has been shown to be highly associated with acetylcholine. However, the influence of acetylcholine on the transient outward potassium current in cerebral cortical neurons remains poorly understood. OBJECTIVE： To investigate acetylcholine modulation on transient outward potassium current in rat parietal cortical neurons using the whole-cell patch-clamp technique. DESIGN, TIME AND SETTING： A neuroelectrophysiology study was performed at the Department of Physiology, Harbin Medical University between January 2005 and January 2006. MATERIALS： Wistar rats were provided by the Animal Research Center, the Second Hospital of Harbin Medical University; PC-IIC patch-clamp amplifier and IBBClamp data collection analysis system were provided by Huazhong University for Science and Technology, Wuhan, China; PP-83 microelectrode puller was purchased from Narrishage, Japan. METHODS： The parietal somatosensory cortical neurons were acutely dissociated, and the modulation of acetylcholine （0.1, 1, 10, 100 μmol/L） on transient outward potassium channel was recorded using the whole-cell patch-clamp technique. MAIN OUTCOME MEASURES： Influence of acetylcholine on transient outward potassium current, potassium channel activation, and inactivation. RESULTS： The inhibitory effect of acetylcholine on transient outward potassium current was dose- and voltage-dependent （P 〈 0.01）. Acetylcholine was found to significantly affect the activation process of transient outward potassium current, i.e., the activation curve of transient outward potassium current was left-shifted, while the inactivation curve was shifted to hyperpolarization. Acetylcholine significantly prolonged the time constant of recovery from inactivation of transient outward potassium current （P 〈 0.01）. CONCLUSION： These results suggest that acetylcholine inhibits transient outward potassium current by regulating activation and inactivation processes of the transient outward potassium channel.

Effects of Acute Mechanical Stretch on the Expression of Mechanosensitive Potassium Channel TREK-1 in Rat Left Ventricle

To explore the role of mechanosensitive potassium channel TREK-1, Western blot analysis was used to investigate the expression changes of TREK-1 in left ventricle in acute mechanically stretched heart. Forty Wistar rats were randomly divided into 8 groups （n=5 in each group）, subject to single Langendorff perfusion for 0, 30, 60, 120 min and acute mechanical stretch for 0, 30, 60, 120 min respectively. With Langendorff apparatus, an acute mechanically stretched heart model was established. There was no significant difference in the expression of TREK-1 among single Langendorff perfusion groups （P〉0.05）. As compared to non-stretched Langendorff-perfused heart, only the expression of TREK-1 in acute mechanically stretched heart （120 min） was greatly increased （P〈0.05）. This result suggested that some course of mechanical stretch could up-regulate the expression of TREK-1 in left ventricle. TREK-1 might play an important role in mechanoelectric feedback, so it could reduce the occurrence of arrhythmia that was induced by extra mechanical stretch.

Chronic salt-loading downregulates large-conductance Ca^(2+)-activated potassium channel in mesenteric arterial smooth muscle cells from SD rats

Objective Large-conductance calcium-activated potassium(BKCa)channel modulates vascular smooth muscle tone.In the present study,we tested the hypothesis that salt,one of the factors which significantly influence blood pressure(BP),can regulate BKCa activity and then elevate blood pressure.Methods Male Sprague-Dawley rats aged 6 weeks were randomized into high salt diet group(HS)and control group,fed with high salt diet(containing 5% NaCl)and standard rat chow(containing 0.4% NaCl)respectively for 16 weeks.Tail systolic blood pressure(SBP),body weight(BW)and 24-hour urinary output were tested every 4 weeks.Content of urinary Na+ was detected using flame spectrophotometrical method.At the end of 16 weeks,all the rats were killed,the mesenteric arteries were obtained,and single mesenteric smooth muscle cells were isolated at once.The resting membrane potential(Em),the total potassium currents and the currents after perfusion with TEA solution of the cells were all recorded by whole cell patch clamp.The transcriptions of BKCa channel α and β1 subunits in mesenteric arterial vascular smooth muscle cells(VSMC)of each group were calculated by real-time RT-PCR.Results There was no difference in SBP and BW at each stage between control group and HS group;the urinary Na+ level in HS animals was elevated significantly after 4 weeks.The negative values of Em in HS group VSMCs were reduced compared with those in the control group.Transcriptions of β1 subunit of BKCa channels were decreased in HS group,but α subunit transcriptions did not differ between the two groups.Whole cell potassium currents did not differ between HS and control groups,but BKCa currents of HS group VSMCs were lower than those of control group ones.Conclusion Even without elevating SBP,salt-loading can still modulate the expression and activity of BKCa channel in the mesenteric arterial VSMC and elevate vascular tone.

The Effects of Protein Kinase C (PKC) on the Tension of Normal and Passively Sensitized Human Airway Smooth Muscle and the Activity of Voltage-dependent Delayed Rectifier Potassium Channel (Kv)

The effects of protein kinase C （PKC） on the tension and the activity of voltage-dependent delayed rectifier potassium channel （K,,） were examined in normal and passively sensitized human airway smooth muscle （HASM）, by measuring tones and whole-cell patch clamp techniques, and the Kv activities and membrane potential （Em） were also detected. The results showed that phorbol 12-myristate 13-acetate （PMA）, a PKC activator, caused a concentration-dependent constriction in normal HASM rings. The constriction of the passively sensitized muscle in asthma serum group was significantly higher than that of the normal group （P〈0.05）, and the constrictions of both groups were completely abolished by PKC inhibitor Ro31-8220 and calcium channel inhibitor nifedipine. Kv activities of HASM cells were significantly inhibited by PMA, and the Em became more positive, as compared with the DMSO （a PMA menstruum）-treated group （P〈0.01）. This effect could be blocked by Ro31-8220 （P〈0.01 ）. It was concluded that activation of PKC could increase the tones of HASM, which might be related to the reduced Kv activity. In passively sensitized HASM rings, this effect was more notable.

Short Review of Ischemia- and Hypoxia-Protective Roles of “Big Potassium” (BK) Channels

There is accumulating evidence that the subfamily of large-conductance potassium (“big”, “BK”) channels are involved in diverse, and perhaps coordinated, protective or counteractive responses to local or generalized ischemia and hypoxia. Although widely distributed, the physiological differences among BK channels which results from posttranslational modification (alternative splicing) and co-assembly with auxiliary modulatory subunits (β1-4 and γ1-4), bestows localized differences in subunit composition, distribution, 2nd-messenger coupling, and pharmacologic properties. Due to the ubiquitous nature of BK channels and the multiplicity of subtypes, they have many potential therapeutic applications in the maintenance of oxygen homeostasis, cerebro- and cardio-protection, and stimulation of respiration in response to drug-induced respiratory depression. BK channels may also offer other potentially broad and underrecognized promising targets for novel pharmaceutical development.

Effect of genistein on voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells

AIM： To investigate the action of genistein （GST）, a broad spectrum tyrosine kinase inhibitor, on voltagegated potassium channels in guinea pig proximal colon smooth muscle cells. METHODS： Smooth muscle cells in guinea pig proximal colon were enzymatically isolated. Nystatin-perforated whole cell patch clamp technique was used to record potassium currents including fast transient outward current （Ikto） and delayed rectifier current （Ikdr）, tWO of which were isolated pharmacologically with 10 mmol/L tetraethylammonium or 5 mmol/L 4-aminopyridine. Contamination of calcium-dependent potassium currents was minimized with no caldum and 0.2 mmol/L CdCl2 in an external solution. RESULTS： GST （10-100 μmol/L） reversibly and dosedependently reduced the peak amplitude of Ikto with an IC50 value of 22.0±6.9 μmol/L. To a lesser extent, Ikdr, was also inhibited in both peak current and sustained current. GST could not totally block the outward potassium current as a fraction of the outWard potassium current, which was insensitive to GST. GST had no effect on the steady-state activation （n =6） and inactivation kinetics （n =6） of Ikto. Sodium orthovanadate （1 retool/L）, a potent inhibitor of tyrosine phosphatase, significantly inhibited GST-induced inhibition （P〈 0.05）. CONCLUSION： GST can dose-dependently and reversibly block voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells.