Renal outer medullary potassium (ROMK) channel is an important K⁺ excretion channel in the body, and K⁺ secreted by the ROMK channels is most or all source of urinary potassium. Previous studies focused on the ROMK channels of thick ascending limb (TAL) and collecting duct (CD), while there were few studies on the involvement of ROMK channels of the late distal convoluted tubule (DCT2) in K⁺ excretion. The purpose of the present study was mainly to record the ROMK channels current in renal DCT2 and observe the effect of high potassium diet on the ROMK channels by using single channel and whole-cell patch-clamp techniques. The results showed that a small conductance channel current with a conductance of 39 pS could be recorded in the apical membrane of renal DCT2, and it could be blocked by Tertiapin-Q (TPNQ), a ROMK channel inhibitor. The high potassium diet significantly increased the probability of ROMK channel current occurrence in the apical membrane of renal DCT2, and enhanced the activity of ROMK channel, compared to normal potassium diet (P < 0.01). Western blot results also demonstrated that the high potassium diet significantly up-regulated the protein expression levels of ROMK channels and epithelial sodium channel (ENaC), and down-regulated the protein expression level of Na⁺-Cl^- cotransporter (NCC). Moreover, the high potassium diet significantly increased urinary potassium excretion. These results suggest that the high potassium diet may activate the ROMK channels in the apical membrane of renal DCT2 and increase the urinary potassium excretion by up-regulating the expression of renal ROMK channels.
Potassium Channels, Inwardly Rectifying/metabolism* ; Kidney Tubules, Distal/metabolism* ; Potassium/metabolism* ; Epithelial Sodium Channels/metabolism* ; Diet

OBJECTIVES: Epilepsy is a syndrome of central nervous system dysfunction caused by many reasons, which is mainly characterized by abnormal discharge of neurons in the brain. Therefore, finding new targets for epilepsy therapy has always been the focus and hotspot in neurological research field. Studies have found that 2-deoxy-D-glucose (2-DG) exerts anti-epileptic effect by up-regulation of K_ATP channel subunit Kir6.1, Kir6.2 mRNA and protein. By using the database of TargetScan and miRBase to perform complementary pairing analysis on the sequences of miRNA and related target genes, it predicted that miR-194 might be the upstream signaling molecule of K_ATP channel. This study aims to explore the mechanism by which 2-DG exerts its anti-epileptic effect by regulating K_ATP channel subunits Kir6.1 and Kir6.2 via miR-194. METHODS: A magnesium-free epilepsy model was established and randomly divided into a control group, an epilepsy group (EP group), an EP+2-DG group, and miR-194 groups (including EP+miR-194 mimic, EP+miR-194 mimic+2-DG, EP+miR-194 mimic control, EP+miR-194 inhibitor, EP+miR-194 inhibitor+2-DG, and EP+miR-194 inhibitor control groups). The 2-DG was used to intervene miR-194 mimics, patch-clamp method was used to detect the spontaneous recurrent epileptiform discharges, real-time PCR was used to detect neuronal miR-194, Kir6.1, and Kir6.2 expressions, and the protein levels of Kir6.1 and Kir6.2were detected by Western blotting. RESULTS: Compared with the control group, there was no significant difference in the amplitude of spontaneous discharge potential in the EP group (P>0.05), but the frequency of spontaneous discharge was increased (P<0.05). Compared with the EP group, the frequency of spontaneous discharge was decreased (P<0.05). Compared with the EP+miR-194 mimic control group, the mRNA and protein expressions of Kir6.1 and Kir6.2 in the EP+miR-194 mimic group were down-regulated (all P<0.05). Compared with the EP+miR-194 inhibitor control group, the mRNA and protein expressions of Kir6.1 and Kir6.2 in the EP+miR-194 inhibitor group were up-regulated (all P<0.05). After pretreatment with miR-194 mimics, the mRNA and protein expression levels of K_ATP channel subunits Kir6.1 and Kir6.2 were decreased (all P<0.05). Compared with the EP+2-DG group, the mRNA and protein expression levels of Kir6.1 and Kir6.2 in the EP+miR-194 mimic+2-DG group were down-regulated (all P<0.05) and the mRNA and protein expression levels of Kir6.1 and Kir6.2 in the EP+miR-194 inhibitor+2-DG group were up-regulated (all P<0.05). CONCLUSIONS The 2-DG might play an anti-epilepsy effect by up-regulating K_ATP channel subunits Kir6.1 and Kir6.2via miR-194.
Adenosine Triphosphate ; Anticonvulsants ; Deoxyglucose/pharmacology* ; Epilepsy/genetics* ; Glucose ; Humans ; MicroRNAs/genetics* ; Potassium Channels, Inwardly Rectifying/metabolism* ; RNA, Messenger/metabolism* ; Signal Transduction

Neuropathic pain is a chronic debilitating symptom characterized by spontaneous pain and mechanical allodynia. It occurs in distinct forms, including brush-evoked dynamic and filament-evoked punctate mechanical allodynia. Potassium channel 2.1 (Kir2.1), which exhibits strong inward rectification, is and regulates the activity of lamina I projection neurons. However, the relationship between Kir2.1 channels and mechanical allodynia is still unclear. In this study, we first found that pretreatment with ML133, a selective Kir2.1 inhibitor, by intrathecal administration, preferentially inhibited dynamic, but not punctate, allodynia in mice with spared nerve injury (SNI). Intrathecal injection of low doses of strychnine, a glycine receptor inhibitor, selectively induced dynamic, but not punctate allodynia, not only in naïve but also in ML133-pretreated mice. In contrast, bicuculline, a GABA receptor antagonist, induced only punctate, but not dynamic, allodynia. These results indicated the involvement of glycinergic transmission in the development of dynamic allodynia. We further found that SNI significantly suppressed the frequency, but not the amplitude, of the glycinergic spontaneous inhibitory postsynaptic currents (gly-sIPSCs) in neurons on the lamina II-III border of the spinal dorsal horn, and pretreatment with ML133 prevented the SNI-induced gly-sIPSC reduction. Furthermore, 5 days after SNI, ML133, either by intrathecal administration or acute bath perfusion, and strychnine sensitively reversed the SNI-induced dynamic, but not punctate, allodynia and the gly-sIPSC reduction in lamina IIi neurons, respectively. In conclusion, our results suggest that blockade of Kir2.1 channels in the spinal dorsal horn selectively inhibits dynamic, but not punctate, mechanical allodynia by enhancing glycinergic inhibitory transmission.
Animals ; Bicuculline ; pharmacology ; Disease Models, Animal ; Glycine ; metabolism ; Hyperalgesia ; drug therapy ; etiology ; metabolism ; Imidazoles ; pharmacology ; Inhibitory Postsynaptic Potentials ; drug effects ; physiology ; Male ; Mice, Inbred C57BL ; Neurons ; drug effects ; metabolism ; Neurotransmitter Agents ; pharmacology ; Peripheral Nerve Injuries ; drug therapy ; metabolism ; Phenanthrolines ; pharmacology ; Potassium Channels, Inwardly Rectifying ; antagonists & inhibitors ; metabolism ; Receptors, GABA-A ; metabolism ; Receptors, Glycine ; metabolism ; Strychnine ; pharmacology ; Synaptic Transmission ; drug effects ; physiology ; Tissue Culture Techniques ; Touch

Basolateral inwardly-rectifying K channels (Kir) play an important role in the control of resting membrane potential and transepithelial voltage, thereby modulating water and electrolyte transport in the distal part of nephron. Kir4.1 and Kir4.1/Kir5.1 heterotetramer are abundantly expressed in the basolateral membrane of late thick ascending limb (TAL), distal convoluted tubule (DCT), connecting tubule (CNT) and cortical collecting duct (CCD). Loss-of-function mutations in KCNJ10 cause EAST/SeSAME syndrome in humans associated with epilepsy, ataxia, sensorineural deafness and water-electrolyte metabolism imbalance, which is characterized by salt wasting, hypomagnesaemia, hypokalaemia and metabolic alkalosis. In contrast, mice lacking Kir5.1 have severe renal phenotype apart from hypokalaemia such as high chlorine metabolic acidosis and hypercalcinuria. The genetic knockout or functional inhibition of Kir4.1 suppresses Na-Cl cotransporter (NCC) expression and activity in the DCT. However, the downregulation of Kir4.1 increases epithelial Na channel (ENaC) expression in the collecting duct. Recently, factors regulating expression and activity of Kir4.1 and Kir4.1/Kir5.1 were identified, such as cell acidification, dopamine, insulin and insulin-like growth factor-1. The involved mechanisms include PKC, PI3K, Src family protein tyrosine kinases and WNK-SPAK signal transduction pathways. Here we review the progress of renal tubule basolateral Kir, and mainly discuss the function and regulation of Kir4.1 and Kir4.1/Kir5.1.
Animals ; Cell Membrane ; Humans ; Kidney Tubules ; metabolism ; Kidney Tubules, Distal ; Membrane Potentials ; Mice ; Potassium Channels, Inwardly Rectifying ; metabolism

ATP-sensitive potassium channels (K) are energy sensors on the plasma membrane. By sensing the intracellular ADP/ATP ratio of β-cells, pancreatic K channels control insulin release and regulate metabolism at the whole body level. They are implicated in many metabolic disorders and diseases and are therefore important drug targets. Here, we present three structures of pancreatic K channels solved by cryo-electron microscopy (cryo-EM), at resolutions ranging from 4.1 to 4.5 Å. These structures depict the binding site of the antidiabetic drug glibenclamide, indicate how Kir6.2 (inward-rectifying potassium channel 6.2) N-terminus participates in the coupling between the peripheral SUR1 (sulfonylurea receptor 1) subunit and the central Kir6.2 channel, reveal the binding mode of activating nucleotides, and suggest the mechanism of how Mg-ADP binding on nucleotide binding domains (NBDs) drives a conformational change of the SUR1 subunit.
Adenosine Triphosphate ; metabolism ; Amino Acid Sequence ; Animals ; Binding Sites ; Cryoelectron Microscopy ; Ligands ; Mesocricetus ; Mice ; Models, Molecular ; Nucleotides ; metabolism ; Pancreas ; metabolism ; Potassium Channels, Inwardly Rectifying ; chemistry ; metabolism ; Protein Binding ; Protein Multimerization ; Protein Structure, Quaternary ; Protein Subunits ; chemistry ; metabolism ; Sf9 Cells ; Spodoptera ; Sulfonylurea Receptors ; chemistry ; metabolism

Age-related hearing loss (AHL) is one of the most common sensory disorders among elderly persons. The inwardly rectifying potassium channel 5.1 (Kir5.1) plays a vital role in regulating cochlear K(+) circulation which is necessary for normal hearing. The distribution of Kir5.1 in C57BL/6J mice cochleae, and the relationship between the expression of Kir5.1 and the etiology of AHL were investigated. Forty C57BL/6J mice were randomly divided into four groups at 4, 12, 24 and 52 weeks of age respectively. The location of Kir5.1 was detected by immunofluorescence technique. The mRNA and protein expression of Kir5.1 was evaluated in mice cochleae using real-time polymerase-chain reactions (RT-PCR) and Western blotting respectively. Kir5.1 was detected in the type II and IV fibrocytes of the spiral ligament in the cochlear lateral wall of C57BL/6J mice. The expression levels of Kir5.1 mRNA and protein in the cochleae of aging C57BL/6J mice were down-regulated. It was suggested that the age-related decreased expression of Kir5.1 in the lateral wall of C57BL/6J mice was associated with hearing loss. Our results indicated that Kir5.1 may play an important role in the pathogenesis of AHL.
Aging ; genetics ; metabolism ; Animals ; Cations, Monovalent ; Fluorescent Antibody Technique ; Gene Expression Regulation ; Ion Transport ; Mice ; Mice, Inbred C57BL ; Microtomy ; Potassium ; metabolism ; Potassium Channels, Inwardly Rectifying ; genetics ; metabolism ; Presbycusis ; genetics ; metabolism ; physiopathology ; RNA, Messenger ; genetics ; metabolism ; Spiral Ligament of Cochlea ; metabolism ; physiopathology ; ultrastructure

OBJECTIVETo investigate the effects of inward rectifier potassium channel blockers (BaCl2, CsCl) on the functions of endothelial progenitor cells (EPCs).

METHODSDensity gradient centrifugation-isolated rat hone marrow mononuclear cells were cultured in vitro. EPCs were harvested and seeded on six culture dish when cells grew to 3-5 passages. Before testing the EPCs were synchronized with M199, which contain 2% fetal calf serum. In the end, EPCs were treated with different intervention. The experiment mainly included two parts: (1) BaCl2 (100 micromol/L) and free BaC2 of Tyrodes solution; (2) CsCl (1 mmol/L) and control. Cell pretreated with blockers above mentioned for 12 h, then the gene expression of stromal cell-derived factor-1 (SDF-1), epoprotenol (PGI2) were assessed, beyond that the ability of adhesion, migration were assayed with different tests. In addition, the medium was collected when EPCs were treated for 3 days. The levels of SDF-1 were measured by sandwich enzyme-linked immunosorbent assay (ELISA). Going even further, EPCs were treated with the signal pathway blockers in advance, after repeat the above steps, in order to analyze the change of SDF-1 and then discuss its mechanism.

RESULTSCompared with control group, BaCl2, CsCl could increase EPC adhesion and migration to same extent. Moreover, the gene expression of SDF-1, PGI2 was significantly up-regulated and the production of SDF-1 increased evidently. Furthermore, the mechanism of SDF-1 secretion increasing mainly was associated with eNOS signaling pathways.

CONCLUSIONBa2+ and Cs+ play important roles in increasing EPCs functions, such as adhesion, migration and secretion.

Animals ; Barium Compounds ; pharmacology ; Cells, Cultured ; Cesium ; pharmacology ; Chemokine CXCL12 ; metabolism ; Chlorides ; pharmacology ; Endothelial Cells ; cytology ; Enzyme-Linked Immunosorbent Assay ; Potassium Channels, Inwardly Rectifying ; antagonists & inhibitors ; physiology ; Rats ; Stem Cells ; cytology

Inwardly rectifying potassium (Kir) channels exhibit an asymmetrical conductance at hyperpolarization (high conductance) compared to depolarization (low conductance). The KCNJ10 gene which encodes an inwardly rectifying K+ channel Kir4.1 subunit plays an essential role in the inner ear and hearing. Mutations or deficiency of KCNJ10 can cause hearing loss with epilepsy, ataxia, sensorineural deafness, and renal tubulopathy (EAST) or SeSAME (seizures, sensorineural deafness, ataxia, mental retardation, and electrolyte imbalance) syndromes. In this review, we mainly focus on the expression and function of Kir4.1 channels in the inner ear and mutation-induced EAST/SeSAME syndromes to provide insight for understanding the pathogenesis of deafness induced by KCNJ10 deficiency.
Deafness ; genetics ; metabolism ; Ear, Inner ; metabolism ; Hearing Loss, Sensorineural ; genetics ; metabolism ; Humans ; Intellectual Disability ; genetics ; metabolism ; Mutation ; Potassium Channels, Inwardly Rectifying ; genetics ; metabolism ; Seizures ; genetics ; metabolism

OBJECTIVETo investigate the relationship between the G protein-gated inward rectifier K+ channel subunit 4 (GIRK4) gene polymorphism and the dyslipidemia among Uyghur residents in Xinjiang.

METHODSThe polymorphisms of rs2604204, rs4937391, rs6590357, and rs11221497 among the Uyghur residents were genotyped using Taqman polymerase chain reaction (PCR). Lipid levels were measured by conventional methods and were analyzed.

RESULTSIn the less-than-50-years population, the genotype distributions of the rs6590357 was statistically significant different in subjects with or without abnormal triglycerides (P=0.005). Aslo, the the genotype distributions of the rs11221497 also significantly differed in subjects with normal compared or abnormal TG (P=0.011). Logistic regression analysis suggested that rs6590357 still had positive association with TG abnormalities in subjects under 50 years (P=0.014). rs11221497 also had positive association with TC abnormalities. The TG levels of CT+TT genotypes were significantly higher than the CC group (P=0.006). Haplotype analysis found that the differences of H3 haplotype frequencies between the TG abnormal and normal groups were statistically significant (P=0.007).

CONCLUSIONThe polymorphisms of rs11221497 and rs6590357 of GIRK4 gene may play a role in the development of dyslipidemia in Uygur population.

China ; epidemiology ; Dyslipidemias ; epidemiology ; metabolism ; Genotype ; Humans ; Polymerase Chain Reaction ; Polymorphism, Single Nucleotide ; Potassium Channels, Inwardly Rectifying ; genetics ; Triglycerides

OBJECTIVETo investigate the expression of GIRK4 gene in the kidney tissues of obese rats.

METHODSObese rat models were established using diet-induced method. The GIRK4 protein expression in kidney tissues was determined in 20 obese rats and 10 normal rats using Western blot analysis.

RESULTSThe relative expression level of GIRK4 protein in the kidney tissues of obese rat (1.75±0.42) was significantly lower than that in normal rats (3.37±0.68, P<0.05).

CONCLUSIONGIRK4 has a low protein expression in the kidney tissues of obese rat.

Animals ; Female ; Gene Expression ; Kidney ; metabolism ; Male ; Obesity ; genetics ; metabolism ; Potassium Channels, Inwardly Rectifying ; genetics ; metabolism ; Rats