scholarly journals Stretch-Activated Whole-Cell Currents in Smooth Muscle Cells from Mesenteric Resistance Artery of Guinea-Pig

1997 ◽  
Vol 501 (2) ◽  
pp. 343-353 ◽  
Author(s):  
Motoko Setoguchi ◽  
Yusuke Ohya ◽  
Isao Abe ◽  
Masatoshi Fujishima
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Resistance Artery ◽  
Whole Cell ◽  
Mesenteric Resistance Artery

scholarly journals Properties of single-channel and whole cell Cl− currents in guinea pig detrusor smooth muscle cells

2019 ◽  
Vol 316 (5) ◽  
pp. C698-C710 ◽  
Author(s):  
Viktor Yarotskyy ◽  
John Malysz ◽  
Georgi V. Petkov
Keyword(s):  
Smooth Muscle ◽  
Patch Clamp ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Single Channel ◽  
Muscle Cells ◽  
Niflumic Acid ◽  
Detrusor Smooth Muscle ◽  
Whole Cell ◽  
Whole Cell Patch Clamp

Multiple types of Cl− channels regulate smooth muscle excitability and contractility in vascular, gastrointestinal, and airway smooth muscle cells. However, little is known about Cl− channels in detrusor smooth muscle (DSM) cells. Here, we used inside-out single channel and whole cell patch-clamp recordings for detailed biophysical and pharmacological characterizations of Cl− channels in freshly isolated guinea pig DSM cells. The recorded single Cl− channels displayed unique gating with multiple subconductive states, a fully opened single-channel conductance of 164 pS, and a reversal potential of −41.5 mV, which is close to the ECl of −65 mV, confirming preferential permeability to Cl−. The Cl− channel demonstrated strong voltage dependence of activation (half-maximum of mean open probability, V0.5, ~−20 mV) and robust prolonged openings at depolarizing voltages. The channel displayed similar gating when exposed intracellularly to solutions containing Ca2+-free or 1 mM Ca2+. In whole cell patch-clamp recordings, macroscopic current demonstrated outward rectification, inhibitions by 4,4′-diisothiocyano-2,2′-stilbenedisulfonic acid (DIDS) and niflumic acid, and insensitivity to chlorotoxin. The outward current was reversibly reduced by 94% replacement of extracellular Cl− with I−, Br−, or methanesulfonate (MsO−), resulting in anionic permeability sequence: Cl−>Br−>I−>MsO−. While intracellular Ca2+ levels (0, 300 nM, and 1 mM) did not affect the amplitude of Cl− current and outward rectification, high Ca2+ slowed voltage-step current activation at depolarizing voltages. In conclusion, our data reveal for the first time the presence of a Ca2+-independent DIDS and niflumic acid-sensitive, voltage-dependent Cl− channel in the plasma membrane of DSM cells. This channel may be a key regulator of DSM excitability.

scholarly journals Extracellular pH and intracellular phosphatidylinositol 4,5-bisphosphate control Cl− currents in guinea pig detrusor smooth muscle cells

2019 ◽  
Vol 317 (6) ◽  
pp. C1268-C1277 ◽  
Author(s):  
Viktor Yarotskyy ◽  
John Malysz ◽  
Georgi V. Petkov
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Extracellular Ph ◽  
Complex Nature ◽  
Airway Smooth Muscle Cells ◽  
Detrusor Smooth Muscle ◽  
Patch Clamp Technique ◽  
Whole Cell

Cl− channels serve as key regulators of excitability and contractility in vascular, intestinal, and airway smooth muscle cells. We recently reported a Cl− conductance in detrusor smooth muscle (DSM) cells. Here, we used the whole cell patch-clamp technique to further characterize biophysical properties and physiological regulators of the Cl− current in freshly isolated guinea pig DSM cells. The Cl− current demonstrated outward rectification arising from voltage-dependent gating of Cl− channels rather than the Cl− transmembrane gradient. An exposure of DSM cells to hypotonic extracellular solution (Δ 165 mOsm challenge) did not increase the Cl− current providing strong evidence that volume-regulated anion channels do not contribute to the Cl− current in DSM cells. The Cl− current was monotonically dependent on extracellular pH, larger and lower in magnitude at acidic (5.0) and basic pH (8.5) values, respectively. Additionally, intracellularly applied phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] analog [PI(4,5)P2-diC8] increased the average Cl− current density by approximately threefold in a voltage-independent manner. The magnitude of the DSM whole cell Cl− current did not depend on the cell surface area (cell capacitance) regardless of the presence or absence of PI(4,5)P2-diC8, an intriguing finding that underscores the complex nature of Cl− channel expression and function in DSM cells. Removal of both extracellular Ca2+ and Mg2+ did not affect the DSM whole cell Cl− current, whereas Gd3+ (1 mM) potentiated the current. Collectively, our recent and present findings strongly suggest that Cl− channels are critical regulators of DSM excitability and are regulated by extracellular pH, Gd3+, and PI(4,5)P2.

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