Arrhythmias, Cardiac ; Humans ; Large-Conductance Calcium-Activated Potassium Channels ; Small-Conductance Calcium-Activated Potassium Channels

Humans ; Hypertension ; Large-Conductance Calcium-Activated Potassium Channels

Small and large conductance Ca2+-activated K+ (SKCa and BKCa) channels are implicated in the modulation of neuronal excitability. We investigated how changes in peripheral KCa channel activity affect mechanical sensitivity as well as the afferent fiber type responsible for KCa channel-induced mechanical sensitivity. Blockade of SKCa and BKCa channels induced a sustained decrease of mechanical threshold which was significantly attenuated by topical application of capsaicin onto afferent fiber and intraplantar injection of 1-ethyl-2-benzimidazolinone. NS1619 selectively attenuated the decrease of mechanical threshold induced by charybdotoxin, but not by apamin. Spontaneous flinching and paw thickness were not significantly different after KCa channel blockade. These results suggest that mechanical sensitivity can be modulated by KCa channels on capsaicin-sensitive afferent fibers.
Apamin ; Capsaicin ; Charybdotoxin ; Hyperalgesia* ; Neurons ; Potassium Channels, Calcium-Activated*

The intermediate conductance Ca2+-activated K+ channels (SK4, IKCa1) are present in lymphocytes, and their membrane expression is upregulated by various immunological stimuli. In this study, the activity of SK4 was compared between Bal-17 and WEHI-231 cell lines which represent mature and immature stages of murine B lymphocytes, respectively. The whole-cell patch clamp with high-Ca2+ (0.8microM) KCl pipette solution revealed a voltage-independent K+ current that was blocked by clotrimazole (1 mM), an SK4 blocker. The expression of mRNAs for SK4 was confirmed in both Bal-17 and WEHI-231 cells. The density of clotrimazole-sensitive SK4 current was significantly larger in Bal-17 than WEHI-231 cells (-11.4+/-3.1 Vs. -5.7+/-1.15 pA/pF). Also, the chronic stimulation of B cell receptors (BCR) by BCR-ligation (anti-IgM Ab, 3microgram/ml, 8~12 h) significantly upregulated the amplitude of clotrimazole-sensitive current from -11.4+/-3.1 to -53.1+/-8.6 pA/pF in Bal-17 cells. In WEHI-231 cells, the effect of BCR-ligation was significantly small (-5.7+/-1.15 to -9.0+/-1.00 pA/pF). The differential expression and regulation by BCR-ligation might reflect functional changes in the maturation of B lymphocytes.
B-Lymphocytes* ; Cell Line ; Clotrimazole ; Lymphocytes ; Membranes ; Potassium Channels ; Potassium Channels, Calcium-Activated ; RNA, Messenger

PURPOSE: This study was performed to determine the effects of phytoestrogen on seminal vesicle excitability. MATERIALS AND METHODS: Single smooth muscle cells of seminal vesicle were obtained from rabbits using proteolytic enzymes(collagenase). Using single cell and channel recording methods of patch clamp, the various currents of potassium channels in smooth muscle cells were recorded. Potassium currents were divided into calcium dependent and independent. RESULTS: Most of the calcium dependent K currents were maxi-K currents and most of calcium independent ones were delayed rectifier K currents. Inside-out patch clamp technique was used to characterize the maxi-K channel. The channel showed outward rectification and calcium dependency. The single-channel conductance of this channel estimated from slope conductance was 119.4+/-11.7 pS under physiological conditions. These characteristics were typical properties of maxi-K channels. Application of genistein(10micronM) rarely affected the delayed rectifier K channel activities, but it evoked significant increase of maxi-K channel activities at both single cell and channel levels. CONCLUSIONS: From these results it is strongly suggested that the excitability and contractility of seminal vesicle might be modulated by genistein through a mechanism of maxi-K channel activation.
Calcium ; Genistein ; Large-Conductance Calcium-Activated Potassium Channels ; Muscle, Smooth* ; Myocytes, Smooth Muscle* ; Phytoestrogens* ; Potassium Channels* ; Potassium* ; Rabbits ; Seminal Vesicles*

PURPOSE: Familial hypokalemic periodic paralysis (HOKPP) is an autosomal dominant channelopathy characterized by episodic attacks of muscle weakness and hypokalemia. Mutations in the calcium channel gene, CACNA1S, or the sodium channel gene, SCN4A, have been found to be responsible for HOKPP; however, the mechanism that causes hypokalemia remains to be determined. The aim of this study was to improve the understanding of this mechanism by investigating the expression of calcium-activated potassium (KCa) channel genes in HOKPP patients. METHODS: We measured the intracellular calcium concentration with fura-2-acetoxymethyl ester in skeletal muscle cells of HOKPP patients and healthy individuals. We examined the mRNA and protein expression of KCa channel genes (KCNMA1, KCNN1, KCNN2, KCNN3, and KCNN4) in both cell types. RESULTS: Patient cells exhibited higher cytosolic calcium levels than normal cells. Quantitative reverse transcription polymerase chain reaction analysis showed that the mRNA levels of the KCa channel genes did not significantly differ between patient and normal cells. However, western blot analysis showed that protein levels of the KCNMA1 gene, which encodes KCa1.1 channels (also called big potassium channels), were significantly lower in the membrane fraction and higher in the cytosolic fraction of patient cells than normal cells. When patient cells were exposed to 50 mM potassium buffer, which was used to induce depolarization, the altered subcellular distribution of BK channels remained unchanged. CONCLUSION: These findings suggest a novel mechanism for the development of hypokalemia and paralysis in HOKPP and demonstrate a connection between disease-associated mutations in calcium/sodium channels and pathogenic changes in nonmutant potassium channels.
Blotting, Western ; Calcium ; Calcium Channels ; Channelopathies ; Cytosol ; Humans ; Hypokalemia ; Hypokalemic Periodic Paralysis* ; Large-Conductance Calcium-Activated Potassium Channels ; Membranes ; Muscle Weakness ; Muscle, Skeletal ; Paralysis ; Polymerase Chain Reaction ; Potassium ; Potassium Channels ; Potassium Channels, Calcium-Activated* ; Reverse Transcription ; RNA, Messenger ; Sodium Channels

PURPOSE: Recent studies have shown that potassium (K+) and sodium channels are involved in prostate cell growth. However, a great many of the studies have been done in prostate cancer cell lines and there are only scant studies on prostate cancer and benign prostatic hypertrophy (BPH) tissue. The present study was aimed to evaluate the alterations of the calcium-activated K+ channel (KCa) expression in prostate cancer, and to compare them with the expression profiles in human BPH tissue to understand their potential role in the progression of prostate cancer. MATERIALS AND METHODS: The prostate tissues obtained from radical prostatectomy (n=10) and transurethral resection of the prostate (n=18) were quickly frozen in liquid nitrogen for the RNA measurements. The protein and mRNA levels of the KCa subtypes and connexins were measured by performing immunoblot analysis and reverse-transcription polymerase chain reaction, respectively. RESULTS: The mRNA levels of type 2 (SK2) and type 3 (SK3) small-conductance and large-conductance (BK) KCas in the prostate cancer tissues were decreased more than 50% compared with those in the BPH samples. In addition, the BK and SK2 protein levels in prostate cancer were also significantly lower than those in the BPH. As reported previously, the connexin 26 and 43 transcript signals in the prostate cancer were significantly reduced compared with those in the BPH samples. CONCLUSIONS: These results suggest that the impaired expression of KCas may have a role in tumor progression via aberrant and uncontrolled prostate cell growth.
Cell Line ; Connexins ; Humans* ; Large-Conductance Calcium-Activated Potassium Channels ; Nitrogen ; Polymerase Chain Reaction ; Potassium ; Potassium Channels, Calcium-Activated* ; Prostate* ; Prostatectomy ; Prostatic Hyperplasia ; Prostatic Neoplasms* ; RNA ; RNA, Messenger ; Small-Conductance Calcium-Activated Potassium Channels ; Sodium Channels

Humans ; Large-Conductance Calcium-Activated Potassium Channels ; TRPC Cation Channels ; Vasodilation

Neuronal firing patterns and frequencies determine the nature of encoded information of the neurons. Here we discuss the molecular identity and cellular mechanisms of spike-frequency adaptation in central nervous system (CNS) neurons. Calcium-activated potassium (K(Ca)) channels such as BK(Ca) and SK(Ca) channels have long been known to be important mediators of spike adaptation via generation of a large afterhyperpolarization when neurons are hyper-activated. However, it has been shown that a strong hyperpolarization via these KCa channels would cease action potential generation rather than reducing the frequency of spike generation. In some types of neurons, the strong hyperpolarization is followed by oscillatory activity in these neurons. Recently, spike-frequency adaptation in thalamocortical (TC) and CA1 hippocampal neurons is shown to be mediated by the Ca²⁺-activated Cl- channel (CACC), anoctamin-2 (ANO2). Knockdown of ANO2 in these neurons results in significantly reduced spike-frequency adaptation accompanied by increased number of spikes without shifting the firing mode, which suggests that ANO2 mediates a genuine form of spike adaptation, finely tuning the frequency of spikes in these neurons. Based on the finding of a broad expression of this new class of CACC in the brain, it can be proposed that the ANO2-mediated spike-frequency adaptation may be a general mechanism to control information transmission in the CNS neurons.
Action Potentials ; Brain ; Central Nervous System* ; Fires ; Neurons* ; Potassium ; Potassium Channels, Calcium-Activated

The alpha9alpha10 nicotinic acetylcholine receptors (nAChRs) mediates efferent inhibition of hair cell function within the auditory sensory organ. Gating of the nAChRs leads to activation of calcium-dependent potassium channels to hyperpolarize the hair cell. In efferent system, main calcium providers to SK channel are nAChR and synaptic cistern, which contribution to efferent inhibition is different between avian and mammalian species. Calcium permeation is more effective in nAChRs of mammalian cochlea than avian cochlea, and mammalian calcium permeability of nAChRs is about 3 times more than avian hair cell. Thus, mammalian nAChRs is a main component of efferent inhibition in cochlear hair cell system.
Acetylcholine ; Calcium ; Cochlea ; Hair ; Permeability ; Potassium Channels, Calcium-Activated ; Receptors, Nicotinic