To detect the phosphorylation of potassium channel protein (Kv1.2 and Kv1.5) in rat cardiac muscle cells accurately, we applied the combined method of immunoprecipitation and Western blot in this study. Compared with using Western blot alone, the combination of immunoprecipitation and Western blot displayed high sensitivity to detect the activation of potassium channel proteins. Because of its simplicity, quickness and reproducibility, we find that this method was promising for detecting the phosphorylation of Kv1.2 and Kv1.5 proteins or other potassium channel proteins in rat cardiac muscle cells.
Animals ; Blotting, Western ; methods ; Cell Membrane ; metabolism ; Female ; Immunoprecipitation ; methods ; Kv1.2 Potassium Channel ; analysis ; genetics ; metabolism ; Kv1.5 Potassium Channel ; analysis ; genetics ; metabolism ; Male ; Myocytes, Cardiac ; cytology ; metabolism ; Phosphorylation ; Rats ; Rats, Sprague-Dawley

To investigate the role of potassium channels in the pathogenesis of airway hyperresponsiveness induced by cigarette smoking, the alteration in expression of large-conductance calcium-activated potassium channel (BKca) and voltage-dependent delayed rectifier potassium channel (Kv1.5) in bronchial smooth muscle cells were investigated in chronic cigarette smoking rats. Airway responsiveness was determined, hematoxylin and eosin staining, immuno-histochemistry, in-situ hybridization and western blot techniques were used. The results showed: (1) Chronic cigarette smoking down-regulated the protein synthesis and mRNA expression of BKca and Kv1.5 in bronchial and bronchiolar smooth muscles. (2) BKca decreased more markedly than Kv1.5 in bronchi, but there was no difference between them in bronchioli. (3) No changes in the expression of these two potassium channel proteins were found in extracted cell membrane protein from lung tissue. The results suggest that chronic cigarette smoking can down-regulate the levels of BKca and Kv1.5 in rat bronchial smooth muscle cells in vivo, which might contribute to the mechanism of airway hyperresponsiveness induced by cigarette smoking.
Animals ; Bronchi ; metabolism ; Cells, Cultured ; Kv1.5 Potassium Channel ; Male ; Muscle, Smooth ; cytology ; metabolism ; Potassium Channels, Calcium-Activated ; biosynthesis ; genetics ; Potassium Channels, Voltage-Gated ; biosynthesis ; genetics ; RNA, Messenger ; biosynthesis ; genetics ; Rats ; Rats, Sprague-Dawley ; Smoking ; adverse effects

AIMTo study the mRNA expression changes in the brain of rats after middle cerebral artery occlusion.

METHODSMiddle cerebral artery occlusion was used to induce ischemia in rat brain. The mRNA expression of voltage-dependent potassium channel subtypes, including Kv1.4, Kv1.5, Kv2.1 and Kv4.2, were detected in rat hippocampus and cortex by RT-PCR.

RESULTSMiddle cerebral artery occlusion induced a significant neurological injury in rats. After ischemia 2 h, the mRNA of Kv1.4, Kv2.1 and Kv4.2 in hippocampus increased by 50%, 67% and 90% , respectively. And the mRNA of Kv1.4 and Kv4.2 maintained at a high level in hippocampus after ischemia 24 h. In cortex, the mRNA level of all the four subtypes were not changed significantly after ischemia 2 h, but the mRNA of Kv2.1 and Kv4.2 increased by 70% and 62% after ischemia 24 h, respectively.

CONCLUSIONThe mRNA expression levels of voltage-dependent potassium channels were up-regulated in rat hippocampus and cortex after middle cerebral artery occlusion.

Animals ; Brain ; metabolism ; Infarction, Middle Cerebral Artery ; metabolism ; Kv1.4 Potassium Channel ; biosynthesis ; genetics ; Kv1.5 Potassium Channel ; biosynthesis ; genetics ; Male ; Potassium Channels, Voltage-Gated ; biosynthesis ; genetics ; RNA, Messenger ; biosynthesis ; genetics ; Rats ; Rats, Wistar ; Shab Potassium Channels ; biosynthesis ; genetics ; Shal Potassium Channels ; biosynthesis ; genetics ; Up-Regulation

BACKGROUNDPotassium (K+) channels are important in regulating cell membrane potential and excitability. Although bronchial myocytes from asthmatic rats show a significant reduction in voltage-dependent delayed rectifier potassium channel (Kv) current density and higher excitability, the activity and expression of Kv in human bronchial smooth muscle cells (HBSMCs) have never been studied. The objective of this study was to investigate the effect of passive sensitization by asthmatic serum on the activity of Kv and the expression of Kv isoform Kv1.5 in HBSMCs.

METHODSHBSMCs were randomly divided into two groups: control group (containing 10% serum from nonatopic individuals) and sensitized group (containing 10% asthmatic serum), then cultured for 24 hours. Whole-cell patch clamp, immunofluorescence staining, reverse transcription-polymerase chain reaction and Western blot techniques were used to study the effect of passive sensitization on the activity of Kv and the expression of Kv1.5 in HBSMCs.

RESULTSThe membrane potential in passively sensitized HBSMCs was significantly depolarized to -(26.7 +/- 5.2) mV compared with -(41.3 +/- 6.4) mV in the control group (P < 0.01). Passive sensitization caused a significant inhibition of Kv currents in HBSMCs, resulting in a downward shift in the current-voltage (I-V) relationship curve. At +50 mV, the peak Kv current density of passively sensitized HBSMCs was significantly decreased from (54.6 +/- 8.7) picoamperes per picofarad (pA/pF) to (32.1 +/- 7.1) pA/pF (P < 0.01). The expression level of Kv1.5 mRNA in passively sensitized HBSMCs was significantly lower than that in the control group (0.76 +/- 0.07 vs 1.04 +/- 0.13, P < 0.05). The expression of Kv1.5 protein of passively sensitized HBSMCs was also significantly reduced compared to that from the control group (984 +/- 168 vs 2200 +/- 380, P < 0.05).

CONCLUSIONSThe activity and expression of Kv were all decreased in HBSMCs passively sensitized by asthmatic serum compared with nonsensitized cells. These changes might be involved in the mechanisms of formation and development of asthma.

Asthma ; blood ; Bronchi ; metabolism ; Cells, Cultured ; Female ; Fluorescent Antibody Technique ; Humans ; Immunization ; Kv1.5 Potassium Channel ; Male ; Myocytes, Smooth Muscle ; metabolism ; Potassium Channels, Voltage-Gated ; analysis ; genetics ; RNA, Messenger ; analysis

OBJECTIVETo investigate the effect of exercise stress on chronic cigarette smoking induced downregulation of large conductance calcium-activated potassium channel (BKca) and voltage-dependent delayed rectifier potassium channel (Kv1.5) expression in pulmonary arterial smooth muscle cells of rats.

METHODSRats were divided into three groups: the normal control group, the smoking control group and the smoking + exercise group. The plasma cortisol level, the potassium channel expression and the pathological changes in lung tissue were determined with HE staining, the immunohistochemistry and the in-situ hybridization.

RESULTS(1) In the smoking + exercise group, the plasma cortisol level was determined immediately after exercise [(1528.7 +/- 469.7) ng/L] and was higher than that determined before exercise [(672.4 +/- 235.7) ng/L] (P < 0.01); (2) The HE staining showed that the chronic pulmonary inflammatory response in the smoking control group was severe while it was mild in the smoking + exercise group; (3) The mRNA and protein expression (OD value) of BKca in the smoking control group (mRNA: 0.2206 +/- 0.0415 for big artery and 0.3935 +/- 0.1378 for small artery; protein: 0.2634 +/- 0.1219 for big artery and 0.0995 +/- 0.0851 for small artery) were less than those in the normal control group. The mRNA expression of BKca in the smoking + exercise group (OD value) (0.5022 +/- 0.1134 for big artery and 0.6408 +/- 0.2135 for small artery) was higher than that in the smoking control group; (4) The mRNA and protein expression of Kv1.5 in the smoking control group (OD value) (mRNA: 0.9354 +/- 0.3290 for big artery and 0.5012 +/- 0.1170 for small artery; protein: 1.1112 +/- 0.3310 for big artery and 0.4736 +/- 0.1250 for small artery) were less than those in the normal control group. The protein expression of Kv1.5 in the smoking + exercise group (0.7445 +/- 0.2690) in small artery was higher than that in the smoking control group.

CONCLUSIONProper exercise stress can decrease inhibition effect of the chronic smoking on the expression of potassium channel BKca and Kv1.5, which perhaps partly results from exercise induced increase of cortisol secretion.

Animals ; Down-Regulation ; Hydrocortisone ; blood ; Kv1.5 Potassium Channel ; biosynthesis ; genetics ; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits ; Male ; Movement ; physiology ; Muscle, Smooth, Vascular ; metabolism ; Potassium Channels ; biosynthesis ; genetics ; Pulmonary Artery ; metabolism ; RNA, Messenger ; genetics ; Rats ; Rats, Sprague-Dawley ; Smoking ; adverse effects

PURPOSE: Pulmonary Kv channels are thought to play a crucial role in the regulation of cell proliferation and apoptosis. Previous studies have shown that fluoxetine upregulated the expression of Kv1.5 and prevented pulmonary arterial hypertension in monocrotaline-induced or hypoxia-induced rats and mice. The current study was designed to test how fluoxetine regulates Kv1.5 channels, subsequently promoting apoptosis in human PASMCs cultured in vitro. MATERIALS AND METHODS: Human PASMCs were incubated with low-serum DMEM, ET-1, and fluoxetine with and without ET-1 separately for 72 h. Then the proliferation, apoptosis, and expression of TRPC1 and Kv1.5 were detected. RESULTS: In the ET-1 induced group, the upregulation of TRPC1 and down regulation of Kv1.5 enhanced proliferation and anti-apoptosis, which was reversed when treated with fluoxetine. The decreased expression of TRPC1 increased the expression of Kv1.5, subsequently inhibiting proliferation while promoting apoptosis. CONCLUSION: The results from the present study suggested that fluoxetine protects against big endothelin-1 induced anti-apoptosis and rescues Kv1.5 channels in human pulmonary arterial smooth muscle cells, potentially by decreasing intracellular concentrations of Ca2+.
Apoptosis/drug effects/genetics ; Blotting, Western ; Cell Proliferation/drug effects ; Cells, Cultured ; Endothelin-1/*pharmacology ; Flow Cytometry ; Fluoxetine/*pharmacology ; Humans ; Kv1.5 Potassium Channel/genetics/*metabolism ; Muscle, Smooth, Vascular/*cytology/drug effects ; Pulmonary Artery/*cytology ; Reverse Transcriptase Polymerase Chain Reaction

AIMTo observe the effect of subtypes of Kv channels in rat pulmonary artery smooth muscle cells (PASMCs) on the process of pulmonary vasoconstriction induced by 15-HETE.

METHODSIn the present study, ring of rabbit PA with specific Kv channel blockers were employed to functionally identify certain channel subtypes that took part in the process of 15-HETE induced pulmonary vasoconstriction; RT-PCR and Western blotting analysis were also used to measure the expression of subtypes of Kv in PASMCs exposed to 15-HETE,chronic hypoxia.

RESULTSBlocking of Kv1. 1, Kv1. 2, Kv1. 3 and Kv1. 6 channels did not affect 15-HETE induced vasoconstriction in normoxic rats; 15-HETE did not affect expression of Kv1. 1 and Kv1. 2 channels; 15-HETE significantly downregulated the expression of mRNA and protein of Kv1. 5 and Kv2. 1 in rat PASMCs.

CONCLUSIONThe results suggested that hypoxia may block Kv1. 5 and Kv2. 1 channels via 15-HETE mediated mechanism, leading to decrease numbers of functional Kv1. 5 and Kv2. 1 channels in PASMCs, leading to PA vasoconstriction.

Animals ; Cell Hypoxia ; Cells, Cultured ; Hydroxyeicosatetraenoic Acids ; pharmacology ; Hypoxia ; physiopathology ; Kv1.5 Potassium Channel ; biosynthesis ; genetics ; Male ; Muscle, Smooth, Vascular ; cytology ; Myocytes, Smooth Muscle ; cytology ; metabolism ; Potassium Channels, Voltage-Gated ; antagonists & inhibitors ; Pulmonary Artery ; physiopathology ; RNA, Messenger ; biosynthesis ; genetics ; Rats ; Rats, Wistar ; Shab Potassium Channels ; biosynthesis ; genetics ; Vasoconstriction ; drug effects

The effect of protein kinase C (PKC) signaling pathway on the activity of voltage-dependent delayed rectifier potassium channel (K(V)) and the expression of K(V) isoform K(V)1.5 in rat bronchial smooth cells (BSMCs) were investigated with whole-cell patch clamp, Western-blot and RT-PCR techniques. The results showed: (1) phorbol 12-myristate 13-acetate (PMA), a PKC activator, caused a significant inhibition of K(V) channel currents in rat BSMCs. The inhibition was partly abolished by Ro31-8220, a PKC inhibitor. (2) PMA caused a significant suppression of the expression of K(V)1.5 mRNA and protein in rat BSMCs. These effects were attenuated by Ro31-8220. The results suggest that in rat BSMCs PKC activation inhibits K(V) currents and down-regulates the expression of K(V)1.5.
Animals ; Bronchi ; cytology ; Cells, Cultured ; Female ; Indoles ; pharmacology ; Kv1.5 Potassium Channel ; genetics ; physiology ; Male ; Membrane Potentials ; physiology ; Myocytes, Smooth Muscle ; cytology ; physiology ; Patch-Clamp Techniques ; Protein Kinase C ; metabolism ; physiology ; RNA, Messenger ; genetics ; metabolism ; Rats ; Rats, Sprague-Dawley ; Tetradecanoylphorbol Acetate ; pharmacology