Inhibition of Ca2+-activated K+ channels by tyrosine phosphatase inhibitors in rat mesenteric artery

2000 ◽  
Vol 78 (9) ◽  
pp. 745-750 ◽  
Author(s):  
Hisashi Yokoshiki ◽  
Takashi Seki ◽  
Masanori Sunagawa ◽  
Nicholas Sperelakis
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Mesenteric Artery ◽  
Single Channel ◽  
Tyrosine Phosphatase ◽  
Phosphatase Inhibitors ◽  
Rat Mesenteric Artery ◽  
Dependent Signal ◽  
Single Channel Currents ◽  
Channel Currents

To investigate the possible regulation of large-conductance Ca2+-activated K+ channels (BKCa) by tyrosine phosphatases (Tyr-PPs), single-channel currents of myocytes from rat mesenteric artery were recorded in open cell-attached patches. Two structurally different Tyr-PP inhibitors, sodium orthovanadate (Na3VO4) and dephostatin, were used. The channels (236 pS) evoked at +40 mV and pCa 6, were significantly inhibited by 1 mM Na3VO4 (-81 ± 3%, n = 10; P < 0.005). Similarly, 100 µM dephostatin strongly inhibited the BKCa channels (-80 ± 7%, n = 7 ; P < 0.05). Therefore, BKCa channels in vascular smooth muscle cells may be regulated by tyrosine phosphatase-dependent signal transduction pathways, whose inhibition could attenuate the channel activity.Key words: Ca2+-activated K+ channel, vascular smooth muscle, tyrosine phosphatase, vanadate, dephostatin.

Dihydropyridine-sensitive calcium channels expressed in canine colonic smooth muscle cells

1993 ◽  
Vol 264 (3) ◽  
pp. C745-C754 ◽  
Author(s):  
A. Rich ◽  
J. L. Kenyon ◽  
J. R. Hume ◽  
K. Overturf ◽  
B. Horowitz ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Calcium Channels ◽  
Smooth Muscle Cells ◽  
Calcium Current ◽  
Single Channel ◽  
Muscle Cells ◽  
Open Probability ◽  
Boltzmann Function ◽  
Single Channel Currents ◽  
Channel Currents

Experiments were performed to identify and characterize the types of calcium channels that regulate inward calcium current in canine colonic smooth muscle. Freshly dispersed smooth muscle cells from the circular layer of the canine proximal colon were used. Single-channel currents were measured with 80 mM Ba2+ as the charge carrier. Small-conductance (10 +/- 2 pS, EBa = 46 +/- 11 mV, n = 9) and large-conductance (21 +/- 1 pS, EBa = 52 +/- 3 mV, n = 19) single-channel currents were observed during depolarizing voltage steps positive to -30 mV. Both types of single-channel currents were inhibited by the addition of 10(-6) M nifedipine to the bath solution. The smaller current was infrequently observed and therefore was not further characterized. Open probability (P(o)) of the larger current amplitude was strongly dependent on voltage. Activation curves were well described by a Boltzmann function with half activation occurring at 4 mV, and a 5-mV increase in membrane potential resulted in an e-fold increase in P(o). BAY K 8644 (1 microM) shifted the activation curve to the left while nifedipine (1 microM) resulted in a right shift. Molecular analysis showed that only the C class of Ca2+ channel alpha 1-subunit is expressed in this tissue. Furthermore, only a single splice variant (rbc-II) was observed. The results suggest that a single class of dihydropyridine-sensitive calcium channels regulates inward calcium current in canine colonic smooth muscle cells.

Hydrogen sulfide-induced relaxation of resistance mesenteric artery beds of rats

2004 ◽  
Vol 287 (5) ◽  
pp. H2316-H2323 ◽  
Author(s):  
Youqin Cheng ◽  
Joseph Fomusi Ndisang ◽  
Guanghua Tang ◽  
Kun Cao ◽  
Rui Wang
Keyword(s):  
Smooth Muscle ◽  
Hydrogen Sulfide ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Mesenteric Artery ◽  
Muscle Cells ◽  
Mesenteric Arteries ◽  
Vascular Effects ◽  
Rat Mesenteric Artery

Hydrogen sulfide (H2S) has been shown recently to function as an important gasotransmitter. The present study investigated the vascular effects of H2S, both exogenously applied and endogenously generated, on resistance mesenteric arteries of rats and the underlying mechanisms. Both H2S and NaHS evoked concentration-dependent relaxation of in vitro perfused rat mesenteric artery beds (MAB). The sensitivity of MAB to H2S (EC50, 25.2 ± 3.6 μM) was about fivefold higher than that of rat aortic tissues. Removal of endothelium or coapplication of charybdotoxin and apamin to endothelium-intact MAB significantly reduced the vasorelaxation effects of H2S. The H2S-induced relaxation of MAB was partially mediated by ATP-sensitive K+ (KATP) channel activity in vascular smooth muscle cells. Pinacidil (EC50, 1.7 ± 0.1 μM, n = 6) mimicked, but glibenclamide (10 μM, n = 6) suppressed, the vasorelaxant effect of H2S. KATP channel currents in isolated mesenteric artery smooth muscle cells were significantly augmented by H2S. l-Cysteine, a substrate of cystathionine-γ-lyase (CSE), at 1 mM increased endogenous H2S production by sixfold in rat mesenteric artery tissues and decreased contractility of MAB. dl-Propargylglycine (a blocker of CSE) at 10 μM abolished l-cysteine-dependent increase in H2S production and relaxation of MAB. Our results demonstrated a tissue-specific relaxant response of resistance arteries to H2S. The stimulation of KATP channels in vascular smooth muscle cells and charybdotoxin/apamin-sensitive K+ channels in vascular endothelium by H2S represents important cellular mechanisms for H2S effect on MAB. Our study also demonstrated that endogenous CSE can generate sufficient H2S from exogenous l-cysteine to cause vasodilation. Future studies are merited to investigate direct contribution of endogenous H2S to regulation of vascular tone.

Inhibition of Ca2+-activated K+ channels by tyrosine phosphatase inhibitors in rat mesenteric artery

2000 ◽  
Vol 78 (9) ◽  
pp. 745-750 ◽  
Author(s):  
Hisashi Yokoshiki ◽  
Takashi Seki ◽  
Masanori Sunagawa ◽  
Nicholas Sperelakis
Keyword(s):  
Mesenteric Artery ◽  
Tyrosine Phosphatase ◽  
Phosphatase Inhibitors ◽  
Rat Mesenteric Artery

scholarly journals Functional angiotensin II receptors in cultured vascular smooth muscle cells.

1982 ◽  
Vol 92 (2) ◽  
pp. 289-298 ◽  
Author(s):  
S Gunther ◽  
R W Alexander ◽  
W J Atkinson ◽  
M A Gimbrone
Keyword(s):  
Smooth Muscle ◽  
Angiotensin Ii ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Binding Sites ◽  
Mesenteric Artery ◽  
Primary Cultures ◽  
Cellular Mechanisms ◽  
Rat Mesenteric Artery

To study cellular mechanisms influencing vascular reactivity, vascular smooth muscle cells (VSMC) were obtained by enzymatic dissociation of the rat mesenteric artery, a highly reactive, resistance-type blood vessel, and established in primary culture. Cellular binding sites for the vasoconstrictor hormone angiotensin II (AII) were identified and characterized using the radioligand 125I-angiotensin II. Freshly isolated VSMC, and VSMC maintained in primary culture for up to 3 wk, exhibited rapid, saturable, and specific 125I-AII binding similar to that seen with homogenates of the intact rat mesenteric artery. In 7-d primary cultures, Scatchard analysis indicated a single class of high-affinity binding sites with an equilibrium dissociation constant (Kd) of 2.8 +/- 0.2 nM and a total binding capacity of 81.5 +/- 5.0 fmol/mg protein (equivalent to 4.5 x 10(4) sites per cell). Angiotensin analogues and antagonists inhibited 125I-AII binding to cultured VSMC in a potency series similar to that observed for the vascular AII receptor in vivo. Nanomolar concentrations of native AII elicited a rapid, reversible, contractile response, in a variable proportion of cells, that was inhibited by pretreatment with the competitive antagonist Sar1,Ile8-AII. Transmission electron microscopy showed an apparent loss of thick (12-18 nm Diam) myofilaments and increased synthetic activity, but these manifestations of phenotypic modulation were not correlated with loss of 125I-AII binding sites or hormonal responsiveness. Primary cultures of enzymatically dissociated rat mesenteric artery VSMC thus may provide a useful in vitro system to study cellular mechanisms involved in receptor activation-response coupling, receptor regulation, and the maintenance of differentiation in vascular smooth muscle.

Single calcium channel currents of arterial smooth muscle at physiological calcium concentrations

1992 ◽  
Vol 263 (5) ◽  
pp. C948-C952 ◽  
Author(s):  
M. Gollasch ◽  
J. Hescheler ◽  
J. M. Quayle ◽  
J. B. Patlak ◽  
M. T. Nelson
Keyword(s):  
Smooth Muscle ◽  
Single Channel ◽  
Membrane Potentials ◽  
Ca Channel ◽  
Ca Channels ◽  
Arterial Smooth Muscle ◽  
Voltage Dependent ◽  
High Concentrations ◽  
Single Channel Currents ◽  
Channel Currents

Entry of Ca through voltage-dependent Ca channels is an important regulator of the function of smooth muscle, cardiac muscle, and neurons. Although Ca channels have been extensively studied since the first descriptions of Ca action potentials (P. Fatt and B. Katz. J. Physiol. Lond. 120: 171-204, 1953), the permeation rate of Ca through single Ca channels has not been measured directly under physiological conditions. Instead, single Ca channels have typically been examined using high concentrations (80-110 mM) of another divalent charge carrier, Ba, so as to maximize the amplitude of the single-channel currents. Calculations of unitary currents at 2 mM Ca indicated that the single-channel currents would be immeasurably small (i.e., < 0.1 pA). We provide here the first direct measurements of single Ca channel currents at a physiological Ca concentration. Contrary to earlier estimates, we have found that currents through single Ca channels in arterial smooth muscle are 0.1-0.3 pA at 2 mM Ca and physiological membrane potentials. These relatively large unitary currents permit direct measurement of Ca channel properties under conditions that do not distort their function. Our data also indicate that Ca permeates these channels at relatively high rates in physiological Ca concentrations and membrane potentials.

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