Nucleotide regulation of the voltage-dependent nonselective cation conductance in murine colonic myocytes.

ATP is proposed to be a major inhibitory neurotransmitter in the gastrointestinal (GI) tract, causing hyperpolarization and smooth muscle relaxation. ATP activates small-conductance Ca(2+)-activated K(+) channels that are involved in setting the resting membrane potential and causing inhibitory junction potentials. No reports are available examining the effects of ATP on voltage-dependent inward currents in GI smooth muscle cells.

Functional characterization of novel alternatively spliced ClC-2 chloride channel variants in the heart.

A novel volume-regulated hyperpolarization-activated chloride inward rectifier channel (Cl.ir) was identified in mammalian heart. To investigate whether ClC-2 is the gene encoding Cl.

Quantitative analysis by flow cytometry of interstitial cells of Cajal, pacemakers, and mediators of neurotransmission in the gastrointestinal tract.

Background: Interstitial cells of Cajal (ICCs) are mesenchymal cells that play critical roles in gastrointestinal motility as electrical pacemakers and mediators of neuromuscular neurotransmission. Although depletions of ICCs have been implicated in several gastrointestinal motor disorders, quantification of these cells has been difficult due to their varied morphology, regionally changing network density, and overall scarcity. Our goal was to evaluate flow cytometry (FCM) for the enumeration of ICCs.

Regulation of Kv4.3 currents by Ca2+/calmodulin-dependent protein kinase II.

The voltage-dependent K+ channel 4.3 (Kv4.3) is one of the major molecular correlates encoding a class of rapidly inactivating K+ currents, including the transient outward current in the heart (Ito) and A currents (IA) in neuronal and smooth muscle preparations.

Hypotonic activation of volume-sensitive outwardly rectifying chloride channels in cultured PASMCs is modulated by SGK.

The serum- and glucocorticoid-inducible kinase (SGK) is a serine/threonine protein kinase (PK) transcriptionally regulated by corticoids, serum, and cell volume. SGK regulates cell volume of various cells by effects on Na(+) and K(+) transport through membrane channels. We hypothesized a role for SGK in the activation of volume-sensitive osmolyte and anion channels (VSOACs) in cultured canine pulmonary artery smooth muscle cells (PASMCs).

Conductances responsible for slow wave generation and propagation in interstitial cells of Cajal.

Interstitial cells of Cajal (ICC) are a fundamental component of the pacemaker apparatus of the gastrointestinal (GI) tract. ICC generate pacemaker currents that are the basis for slow wave activity in GI muscles. ICC form a network of cells connected by gap junctions that run around and along the phasic regions of the GI tract.

Carbon monoxide activates KCa channels in newborn arteriole smooth muscle cells by increasing apparent Ca2+ sensitivity of alpha-subunits.

Carbon monoxide (CO) is a gaseous vasodilator produced by many cell types, including endothelial and smooth muscle cells. The goal of the present study was to investigate signaling mechanisms responsible for CO activation of large-conductance Ca(2+)-activated K(+) (K(Ca)) channels in newborn porcine cerebral arteriole smooth muscle cells. In intact cells at 0 mV, CO (3 microM) or CO released from dimanganese decacarbonyl (10 microM), a novel light-activated CO donor, increased K(Ca) channel activity 4.

Mechanism of active repolarization of inhibitory junction potential in murine colon.

Enteric inhibitory responses in gastrointestinal (GI) smooth muscles involve membrane hyperpolarization that transiently reduce the excitability of GI muscles. We examined the possibility that an active repolarization mechanism participates in the restoration of resting membrane potential after fast inhibitory junction potentials (IJPs) in the murine colon. Previously, we showed these cells express a voltage-dependent nonselective cation conductance (NSCC) that might participate in active repolarization of IJPs.

Purification of interstitial cells of Cajal by fluorescence-activated cell sorting.

Interstitial cells of Cajal (ICC) in the gastrointestinal tract generate and propagate slow waves and mediate neuromuscular neurotransmission. Although damages to ICC have been described in several gastrointestinal motor disorders, analysis of their gene expression in health and disease has been problematic because of the difficulties in isolating these cells. Our goal was to develop techniques for large-scale purification of ICC.

Molecular variants of KCNQ channels expressed in murine portal vein myocytes: a role in delayed rectifier current.

We have analyzed the expression of KCNQ genes in murine portal vein myocytes and determined that of the 5 known KCNQ channels, only KCNQ1 was expressed. In addition to the full-length KCNQ1 transcript, a novel spliced form (termed KCNQ1b) was detected that had a 63 amino acid truncation at the C-terminus. KCNQ1b was not detected in heart or brain but represented approximately half the KCNQ1 transcripts expressed in PV.

ERG K+ channels modulate the electrical and contractile activities of gallbladder smooth muscle.

The current study was undertaken to test the existence and possible role of ether-a-go-go-related gene 1 (ERG1) protein K(+) channels in gallbladder smooth muscle (GBSM). Transcripts encoding ERG1 were detected in human, mouse, and guinea pig GBSM, and ERG1 immunoreactivity was observed in GBSM cells. In intracellular voltage recordings, addition of E-4031 (100 nM-1 microM) or cisapride (100 nM-2 microM) caused concentration-dependent excitation of guinea pig GBSM that was not affected by 500 nM TTX + 5 microM atropine, and E-4031 also depolarized the resting membrane potential.

Differential transcriptional expression of Ca2+ BP superfamilies in murine gastrointestinal smooth muscles.

Calmodulin (Cal) plays important roles for contractile activity in smooth muscles. Recently, two distinct Ca(2+)-binding protein superfamilies with sequence similarities to Cal have been identified in neuronal cells: neuronal Ca(2+)-binding proteins (NCBPs) and Cal-like Ca(2+)-binding proteins (CaBPs). Some NCBPs and CaBPs play significant roles for Ca(2+)-dependent cellular signaling in the nervous system.

TRPC4 currents have properties similar to the pacemaker current in interstitial cells of Cajal.

Interstitial cells of Cajal (ICC) are the pacemaker cells responsible for the generation and propagation of electrical slow waves in phasic muscles of the gastrointestinal (GI) tract. The pacemaker current that initiates each slow wave derives from a calcium-inhibited, voltage-independent, nonselective cation channel. This channel in ICC displays properties similar to that reported for the transient receptor potential (TRP) family of nonselective cation channels, particularly those seen for TRPC3 and TRPC4.

Characterization of the A-type potassium current in murine gastric antrum.

A-type currents are rapidly inactivating potassium currents that operate at subthreshold potentials. A-type currents have not been reported to occur in the phasic muscles of the stomach. We used conventional voltage-clamp techniques to identify and characterize A-type currents in myocytes isolated from the murine antrum.

Contribution of Kv4 channels toward the A-type potassium current in murine colonic myocytes.

A rapidly inactivating K(+) current (A-type current; I(A)) present in murine colonic myocytes is important in maintaining physiological patterns of slow wave electrical activity. The kinetic profile of colonic I(A) resembles that of Kv4-derived currents. We examined the contribution of Kv4 alpha-subunits to I(A) in the murine colon using pharmacological, molecular and immunohistochemical approaches.

Microarray comparison of normal and W/Wv mice in the gastric fundus indicates a supersensitive phenotype.

Interstitial cells of Cajal (ICC) have been identified in specific areas throughout the smooth musculature of the gastrointestinal (GI) tract. Located within the circular and longitudinal muscle layers of the gastric fundus lies a specific type of ICC, termed "intramuscular" ICC or IC-IM. The principal function of this cell type is to act as "mediators of excitatory and inhibitory enteric neurotransmission.

ClC-3 is a fundamental molecular component of volume-sensitive outwardly rectifying Cl- channels and volume regulation in HeLa cells and Xenopus laevis oocytes.

Volume-sensitive osmolyte and anion channels (VSOACs) are activated upon cell swelling in most vertebrate cells. Native VSOACs are believed to be a major pathway for regulatory volume decrease (RVD) through efflux of chloride and organic osmolytes. ClC-3 has been proposed to encode native VSOACs in Xenopus laevis oocytes and in some mammalian cells, including cardiac and vascular smooth muscle cells.

Functional and molecular identification of ERG channels in murine portal vein myocytes.

Ion channels encoded by ether-à-go-go-related genes (ERG) have been implicated in repolarization of the cardiac action potential and also as components of the resting membrane conductance in various cells. The aim of the present study was to determine whether ERG channels were expressed in smooth muscle cells isolated from portal vein. RT-PCR demonstrated the expression of murine ERG (mERG), and real-time quantitative PCR showed that the mERG1b isoform predominated over the mERG1a, mERG2, and mERG3 in portal vein.

The large conductance potassium channel beta-subunit can interact with and modulate the functional properties of a calcium-activated chloride channel, CLCA1.

We have recently compared the biophysical and pharmacological properties of native Ca(2+)-activated Cl(-) currents in murine portal vein with mCLCA1 channels cloned from murine portal vein myocytes (Britton, F. C., Ohya, S.

Constitutive expression and function of cyclooxygenase-2 in murine gastric muscles.

Background & Aims: Cyclooxygenase enzymes (COX) generate intermediates in the prostaglandin (PG) cascade. COX-1 is constitutively expressed in many cells, and COX-2 is typically thought to be an inducible isoform.

Methods: We evaluated constitutive expression and function of COX-2 in murine gastric muscles.

Comparison of the properties of CLCA1 generated currents and I(Cl(Ca)) in murine portal vein smooth muscle cells.

Calcium-activated chloride currents (I(Cl(Ca))) have been recorded in various smooth muscle cells but, to date, there has been no information as to the molecular nature of the channel underlying this conductance. We have characterised native I(Cl(Ca)) in freshly dispersed smooth muscle cells isolated from murine portal vein using whole-cell voltage clamp. I(Cl(Ca)) exhibited time-dependent activation at depolarised potentials and rapid deactivation upon repolarisation.