BACKGROUNDAdenomyosis (AM) has impaired contraction. This study aimed to explore the expression of potassium channels related to contraction in myometrial smooth muscle cells (MSMCs) of AM.

METHODSUterine tissue samples from 22 patients (cases) with histologically confirmed AM and 12 (controls) with cervical intraepithelial neoplasia were collected for both immunohistochemistry and real-time polymerase chain reaction to detect the expression of large conductance calcium- and voltage-sensitive K + channel (BKCa)-α/β subunits, voltage-gated potassium channel (Kv) 4.2, and Kv4.3. Student's t-test was used to compare the expression.

RESULTSThe BKCa-α/β subunits, Kv4.2, and Kv4.3 were located in smooth muscle cells, glandular epithelium, and stromal cells. However, BKCa-β subunit expression in endometrial glands of the controls was weak, and Kv4.3 was almost undetectable in the controls. The expression of BKCa-α messenger RNA (mRNA) (0.62 ± 0.19-fold decrease, P < 0.05) and Kv4.3 mRNA (0.67 ± 0.20-fold decrease, P < 0.05) decreased significantly in the MSMCs of the control group compared with the AM group. However, there were no significant differences in BKCa-β subunit mRNA or Kv4.2 mRNA.

CONCLUSIONSThe BKCa-α mRNA and the Kv4.3 mRNA are expressed significantly higher in AM than those in the control group, that might cause the abnormal uterus smooth muscle contractility, change the microcirculation of uterus to accumulate the inflammatory factors, impair the endometrium further, and aggravate the pain.

Adenomyosis ; metabolism ; Adult ; Female ; Humans ; Immunohistochemistry ; Large-Conductance Calcium-Activated Potassium Channels ; metabolism ; Male ; Myocytes, Smooth Muscle ; metabolism ; Potassium Channels, Voltage-Gated ; metabolism ; Real-Time Polymerase Chain Reaction ; Shal Potassium Channels ; metabolism ; Uterine Contraction ; physiology ; Uterine Neoplasms ; metabolism ; Uterus ; metabolism

The aim of the present study was to investigate the role of calcineurin in the down-regulation of left ventricular transmural voltage-dependent K(+) currents in heart failure. Transverse aorta was banded by using microsurgical techniques to create mouse heart failure model. Sham-operated (Sham) or aorta banded (Band) mice were randomized to receive calcineurin inhibitor cyclosporine A (CsA) or vehicle. The densities and kinetic properties of voltage-dependent K(+) currents, as well as action potential (AP), of left ventricular subendocardial (Endo) and subepicardial (Epi) myocytes were determined by using whole-cell patch-clamp technique. The results showed that calcineurin activity was significant higher in Endo myocytes than that in Epi ones in all the groups. Compared with Sham group, Band mice showed significantly increased calcineurin activity both in Endo and Epi myocytes. CsA significantly reduced calcineurin activity in Band mice. CsA treatment in Band mice partially reversed the down-regulation of Ito density, completely reversed the down-regulation of IK,slow density both in Endo and Epi myocytes, and Iss density in Endo myocytes. In addition, CsA treatment in Band mice partially antagonized the prolongation of action potential duration (APD), and APD at 50% (APD50) and 90% repolarization (APD90) were significantly reduced. Because of non-parallel shortening of APD in Endo and Epi myocytes, the ratio of Endo/Epi APD90 was reduced from 4.8:1 in Band mice to 2.6:1 in CsA-treated mice, which was close to that in Sham mice. The results suggest that non-parallel activation of calcineurin in Endo and Epi myocytes contributes to the down-regulation of transmural voltage-dependent K(+) currents and the amplification of transmural dispersion of repolarization (TDR) in left ventricular failure hearts. Inhibition of calcineurin may be a potential new therapeutic strategy to prevent and cure arrhythmias and sudden death in heart failure.
Action Potentials ; Animals ; Calcineurin ; physiology ; Calcineurin Inhibitors ; pharmacology ; Cyclosporine ; pharmacology ; Disease Models, Animal ; Down-Regulation ; Heart ; physiopathology ; Heart Failure ; physiopathology ; Mice ; Patch-Clamp Techniques ; Potassium Channels, Voltage-Gated ; physiology ; Ventricular Function, Left

Cellular excitability is an important physiological factor in maintaining normal cardiac activity. The present study was designed to investigate the ionic mechanism underlying different excitability in atrial and ventricular myocytes of guinea pig heart using a whole-cell patch configuration. We found that excitability is lower in ventricular myocytes than that in atrial myocytes. Although the density of voltage-gated fast Na(+) current (INa) was lower in ventricular myocytes, it would not correlate to the lower excitability since its availability was greater than that in atrial myocytes around threshold potential. Classical inward rectifier K(+) current (IK1) was greater in ventricular myocytes than that in atrial myocytes, which might contribute in part to the lower excitability. In addition, the transient outward K(+) current with inward rectification (Itoir) elicited by depolarization was greater in ventricular myocytes than that in atrial myocytes and might contribute to the lower excitability. In ventricular myocytes, Ba(2+) at 5 µmol/L significantly inhibited Itoir, enhanced excitability, and shifted the threshold potential of INa activation to more negative, and the effect was independent of affecting INa. Our results demonstrate the novel information that in addition to classical IK1, Itoir plays a major role in determining the distinctive excitability in guinea pig atrial and ventricular myocytes and maintaining cardiac excitability. More effort is required to investigate whether increase of Itoir would be protective via reducing excitability.
Animals ; Atrial Function ; Guinea Pigs ; Heart Atria ; cytology ; Heart Ventricles ; cytology ; Myocytes, Cardiac ; physiology ; Potassium Channels, Inwardly Rectifying ; physiology ; Ventricular Function ; Voltage-Gated Sodium Channels ; physiology

Brain growth spurt (BGS) is the critical period of neuronal growth and synaptic connection. The voltage-gated K(+) channel is the key channel for maintenance of cell excitability and information transfer among neurons. The purpose of the present study is to investigate the critical period of voltage-gated K(+) channel development in hippocampal CA1 neurons during the BGS. Changes of voltage-gated K(+) currents in neurons from acutely isolated hippocampal CA1 brain slices of rats at different ages (0-4 weeks after birth) were recorded by the whole-cell patch-clamp technique. The depolarization voltage was set at +90 mV, and 0 week was set as the control group. The experimental results showed that, with increasing ages (1-4 weeks), the maximum current densities of IA increased by (16.14 ± 0.51)%, (81.73 ± 10.71)%, (106.72 ± 5.29)%, (134.58 ± 8.81)% (n = 10, P < 0.05), and the maximum current densities of IK increased by (16.75 ± 3.88)%, (134.01 ± 2.85)%, (180.56 ± 8.49)%, (194.5 ± 8.53)% (n = 10, P < 0.05), respectively, compared with those in 0 week. During 0-4 weeks after birth, the activation kinetics of IA shifted to left, and the half activation voltages of IA were 14.67 ± 0.75, 13.46 ± 0.64, 8.39 ± 0.87, 4.60 ± 0.96, 0.54 ± 0.92 (mV, n = 10, P < 0.05), respectively; The activation kinetics of IK shifted to left and the half activation voltages of IK were 8.94 ± 0.85, 6.65 ± 0.89, 0.47 ± 1.15, -1.80 ± 0.89, -8.56 ± 1.08 (mV, n = 10, P < 0.05) respectively. The inactivation kinetics of IA also shifted to left, and the half inactivation voltages were -45.68 ± 1.26, -46.81 ± 0.78, -48.64 ± 0.81, -51.96 ± 1.02, -58.31 ± 1.35 (mV, n = 10) respectively at 0, 1, 2, 3 and 4 weeks after birth, which showed no significant changes between 0 and 1 week, but significant decreases during 1-4 weeks after birth (P < 0.05). These results indicate that the current densities of IA and IK increase and the kinetic characteristics of the voltage-gated K(+) channels change with increasing ages during 0-4 weeks after birth, and the differences are especially significant between the 1st week and the 2nd week after birth. These changes may be related to the maturation of hippocampal neurons and the progress of their functions.
Animals ; CA1 Region, Hippocampal ; cytology ; Membrane Potentials ; Neurons ; physiology ; Patch-Clamp Techniques ; Potassium Channels, Voltage-Gated ; physiology ; Rats

OBJECTIVETo investigate the difference in membrane current of vascular smooth muscle cells (VSMCs) in brain artery (BA) of spontaneously hypertensive rats (SHR) and Wistar rats.

METHODSWe compared the properties of spontaneous transient outward K+ currents (STOCs), the density and composition of current of VSMCs in BA of SHR and Wistar rats by whole-cell patch clamp technique.

RESULTS(1) When the command voltage was 0, + 20, + 40 and + 60 mV respectively, the current densities of VSMCs in BA of SHR and Wistar rats were significant different (P < 0.01). (2) The whole-cell current of VSMCs was partly inhibited by 1 mmol/L4-AP (voltage-gated K+ channel blocker) or 1 mmol/L TEA (big conductance Ca(2+)-activated K+ channel blocker) respectively. (3) The frequency and amplitude of STOCs in SHR were faster and bigger than those in Wistar rats. 1 mmol/L TEA almostly inhibited the STOCs, but not by 4-AP.

CONCLUSIONThese results suggest that the current densities of VSMCs in BA of SHR and Wistar rats are significant different, the outward current of VSMCs in BA of SHR and Wistar rats are composed by Kv and BK(Ca). SHR express more STOCs mediated by BK(Ca), than Wistar rats.

Animals ; Cerebral Arteries ; cytology ; physiology ; Membrane Potentials ; physiology ; Muscle, Smooth, Vascular ; cytology ; physiology ; Myocytes, Smooth Muscle ; physiology ; Patch-Clamp Techniques ; Potassium Channels, Calcium-Activated ; physiology ; Potassium Channels, Voltage-Gated ; physiology ; Rats ; Rats, Inbred SHR ; Rats, Wistar

The influence of hypoxia on the activity of voltage-gated potassium channel in pulmonary artery smooth muscle cells (PASMCs) of rats and its roles in the pathogenesis of chronic pulmonary heart disease were investigated. Eighty male Sprague-Dawley rats were randomly allocated into control group (n=10), acute hypoxic group (n=10), and chronic hypoxic groups (n=60). The chronic hypoxic groups were randomly divided into 6 subgroups (n=10 each) according to the chronic hypoxic periods. The rats in the control group were kept in room air and those in acute hypoxic group in hypoxia environmental chamber for 8 h. The rats in chronic hypoxic subgroups were kept in hypoxia environmental chamber for 8 h per day for 5, 10, 15, 20, 25, and 30 days, respectively. The mean pulmonary arterial pressure (mPAP), right ventricular hypertrophy index (RVHI), and the current of voltage-gated potassium channel (I K) in PASMCs were measured. Results showed that both acute and chronic hypoxia could decrease the I K in PASMCs of rats and the I-V relationship downward shifted to the right. And the peak I K density at +60mV decreased with prolongation of hypoxia exposure. No significant difference was noted in the density of I K (at +60 mV) and I-V relationship between control group and chronic hypoxic subgroup exposed to hypoxia for 5 days (P>0.05), but there was a significant difference between control group and chronic hypoxic subgroup exposed to hypoxia for 10 days (P<0.05). Significant differences were noted in the I K density (at +60 mV) and I-V relationships between control group and chronic hypoxic subgroups exposed to hypoxia for 20 days and 30 days (P<0.01). Compared with control rats, the mPAP and RVHI were significantly increased after chronic exposure to hypoxia for 10 days (P<0.05), which were further increased with prolongation of hypoxia exposure, and there were significant differences between control group and chronic hypoxic subgroups exposed to hypoxia for 20 days and 30 days (P<0.01). Both the mPAP and the RVHI were negatively correlated with the density of I K (r=-0.89769 and -0.94476, respectively, both P<0.01). It is concluded that exposure to hypoxia may cause decreased activity of voltage-gated potassium channel, leading to hypoxia pulmonary vasoconstriction (HPV). Sustained HPV may result in chronic pulmonary hypertension, even chronic pulmonary heart disease, contributing to the pathogenesis of chronic pulmonary heart disease.
Animals ; Blood Pressure ; physiology ; Cell Hypoxia ; physiology ; Cells, Cultured ; Hypertrophy, Right Ventricular ; physiopathology ; Hypoxia ; physiopathology ; Male ; Membrane Potentials ; physiology ; Myocytes, Smooth Muscle ; physiology ; Patch-Clamp Techniques ; Potassium Channels, Voltage-Gated ; physiology ; Pulmonary Artery ; pathology ; physiopathology ; Pulmonary Heart Disease ; physiopathology ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Time Factors ; Vasoconstriction ; physiology

Serotonin (5-hydroxytryptamine (5-HT)) is a neurotransmitter that regulates a variety of functions in the nervous, gastrointestinal and cardiovascular systems. Despite such importance, 5-HT signaling pathways are not entirely clear. We demonstrated previously that 4-aminopyridine (4-AP)-sensitive voltage-gated K+ (Kv) channels determine the resting membrane potential of arterial smooth muscle cells and that the Kv channels are inhibited by 5-HT, which depolarizes the membranes. Therefore, we hypothesized that 5-HT contracts arteries by inhibiting Kv channels. Here we studied 5-HT signaling and the detailed role of Kv currents in rat mesenteric arteries using patch-clamp and isometric tension measurements. Our data showed that inhibiting 4-AP-sensitive Kv channels contracted arterial rings, whereas inhibiting Ca2+-activated K+, inward rectifier K+ and ATP-sensitive K+ channels had little effect on arterial contraction, indicating a central role of Kv channels in the regulation of resting arterial tone. 5-HT-induced arterial contraction decreased significantly in the presence of high KCl or the voltage-gated Ca2+ channel (VGCC) inhibitor nifedipine, indicating that membrane depolarization and the consequent activation of VGCCs mediate the 5-HT-induced vasoconstriction. The effects of 5-HT on Kv currents and arterial contraction were markedly prevented by the 5-HT2A receptor antagonists ketanserin and spiperone. Consistently, alpha-methyl 5-HT, a 5-HT2 receptor agonist, mimicked the 5-HT action on Kv channels. Pretreatment with a Src tyrosine kinase inhibitor, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine, prevented both the 5-HT-mediated vasoconstriction and Kv current inhibition. Our data suggest that 4-AP-sensitive Kv channels are the primary regulator of the resting tone in rat mesenteric arteries. 5-HT constricts the arteries by inhibiting Kv channels via the 5-HT2A receptor and Src tyrosine kinase pathway.
4-Aminopyridine/pharmacology ; Action Potentials ; Animals ; Calcium Channel Blockers/pharmacology ; Calcium Channels/metabolism ; Cells, Cultured ; Ketanserin/pharmacology ; Male ; Mesenteric Arteries/drug effects/*metabolism/physiology ; Muscle Contraction ; Muscle, Smooth, Vascular/cytology/drug effects/metabolism/physiology ; Myocytes, Smooth Muscle/drug effects/metabolism/physiology ; Nifedipine/pharmacology ; Potassium Channel Blockers/pharmacology ; Potassium Channels, Voltage-Gated/antagonists & inhibitors/*metabolism ; Protein Kinase Inhibitors/pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptor, Serotonin, 5-HT2A/*metabolism ; Serotonin/*pharmacology ; Serotonin 5-HT2 Receptor Antagonists/pharmacology ; Spiperone/pharmacology ; *Vasoconstriction ; src-Family Kinases/antagonists & inhibitors/*metabolism

Mutation or common intronic variants in cardiac ion channel genes have been suggested to be associated with sudden cardiac death caused by idiopathic ventricular tachyarrhythmia. This study aimed to find mutations in cardiac ion channel genes of Korean sudden cardiac arrest patients with structurally normal heart and to verify association between common genetic variation in cardiac ion channel and sudden cardiac arrest by idiopathic ventricular tachyarrhythmia in Koreans. Study participants were Korean survivors of sudden cardiac arrest caused by idiopathic ventricular tachycardia or fibrillation. All coding exons of the SCN5A, KCNQ1, and KCNH2 genes were analyzed by Sanger sequencing. Fifteen survivors of sudden cardiac arrest were included. Three male patients had mutations in SCN5A gene and none in KCNQ1 and KCNH2 genes. Intronic variant (rs2283222) in KCNQ1 gene showed significant association with sudden cardiac arrest (OR 4.05). Four male sudden cardiac arrest survivors had intronic variant (rs11720524) in SCN5A gene. None of female survivors of sudden cardiac arrest had SCN5A gene mutations despite similar frequencies of intronic variants between males and females in 55 normal controls. Common intronic variant in KCNQ1 gene is associated with sudden cardiac arrest caused by idiopathic ventricular tachyarrhythmia in Koreans.
Adolescent ; Adult ; Aged ; Arrhythmias, Cardiac/genetics ; *Death, Sudden, Cardiac ; Ether-A-Go-Go Potassium Channels/genetics ; Female ; Genetic Markers ; Genetic Predisposition to Disease ; Genetic Variation ; Heart/physiology ; Heart Conduction System/abnormalities ; Humans ; KCNQ1 Potassium Channel/*genetics ; Male ; Middle Aged ; NAV1.5 Voltage-Gated Sodium Channel/*genetics ; Republic of Korea ; Tachycardia, Ventricular/*genetics ; Ventricular Fibrillation/*genetics ; Young Adult

This study is to explore a new method of investigating molecular basis for electrophysiological properties of early fetal cardiomyocytes. Single embryonic cardiomyocytes of mouse early developmental heart (E10.5) were obtained by a collagenase B digestion approach. After recording spontaneous action potential using whole cell patch clamp technique, the single cell was picked by a glass micropipette, followed by a standard RT-PCR to explore the expression levels of several ion channel genes. Three phenotypes of cardiomyocytes were demonstrated with distinct properties: ventricular-like, atrial-like, and pacemaker-like action potentials. Ventricular-like and atrial-like cells were characterized with much negative maximum diastolic potential (MDP) and a higher V(max) (maximum velocity of depolarization) compared to pacemaker-like cells. MDP of ventricular-like cells was the most negative. In parallel, stronger expression of SCN5a, SCN1b and Kir2.1 were observed in ventricular-like and atrial-like cells compared to that of pacemaker-like cells, where Kir2.1 in ventricular-like cells was the most abundant. Cardiomyocytes with distinct electrophysiological properties had distinct gene expression pattern. Single cell RT-PCR combined with patch clamp technique could serve as a precise detector to analyze the molecular basis of the special electrophysiological characteristics of cardiomyocytes.
Animals ; Electrophysiological Phenomena ; Female ; Fetus ; Male ; Mice ; Myocytes, Cardiac ; metabolism ; physiology ; NAV1.5 Voltage-Gated Sodium Channel ; genetics ; metabolism ; Patch-Clamp Techniques ; Potassium Channels, Inwardly Rectifying ; genetics ; metabolism ; Real-Time Polymerase Chain Reaction ; Voltage-Gated Sodium Channel beta-1 Subunit ; genetics ; metabolism

The aim of the present study was to investigate the effect of 18β-glycyrrhetinic acid (18βGA) on the membrane current of vascular smooth muscle cells (VSMCs) in arteriole. Guinea pig anterior inferior cerebellar artery (AICA) and mesenteric artery (MA) were isolated, and single VSMCs were harvested using digestion with papain and collagenase IA. Outward currents of the VSMCs were recorded by whole-cell patch clamp technique. Results were shown as below: (1) 1 mmol/L 4-AP and 1 mmol/L TEA both could partially inhibit the whole-cell current of VSMCs in arterioles. (2) 18βGA inhibited the outward current of VSMCs in a concentration-dependent manner. The inhibitory rates of 10, 30 and 100 μmol/L 18βGA on the membrane current of VSMCs (+40 mV) were (25.3 ± 7.1)%, (43.1 ± 10.4)% and (68.4 ± 3.9)% respectively in AICA, and (13.2 ± 5.6)%, (34.2 ± 4.0)% and (59.3 ± 7.3)% respectively in MA. There was no significant difference between the inhibitory effects of 18βGA on AICA and MA. 18βGA also inhibited the outward current of VSMCs in a voltage-dependent manner. 18βGA induced a more pronounced inhibition of the outward current from 0 to +40 mV, especially at +40 mV. (3) With the pretreatment of 10 mmol/L TEA, the inhibitory effect of 18βGA on the membrane current of VSMCs was significantly abolished. These results suggest that the outward current of VSMCs in arterioles is mediated by voltage-dependent K(+) channels (K(v)) and big conductance calcium-activated K(+) channels (BK(Ca)), which can be inhibited by 18βGA in concentration- and voltage-dependent way.
Animals ; Arterioles ; physiology ; Cerebellum ; blood supply ; Female ; Gap Junctions ; physiology ; Glycyrrhetinic Acid ; analogs & derivatives ; pharmacology ; Guinea Pigs ; In Vitro Techniques ; Male ; Membrane Potentials ; drug effects ; Mesenteric Arteries ; cytology ; physiology ; Muscle, Smooth, Vascular ; cytology ; physiology ; Myocytes, Smooth Muscle ; physiology ; Patch-Clamp Techniques ; Potassium Channels, Calcium-Activated ; physiology ; Potassium Channels, Voltage-Gated ; physiology