51
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Heaps CL, Bowles DK. Gender-specific K(+)-channel contribution to adenosine-induced relaxation in coronary arterioles. J Appl Physiol (1985) 2002; 92:550-8. [PMID: 11796663 DOI: 10.1152/japplphysiol.00566.2001] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the contribution of K(+)-channel activity on basal tone and adenosine-mediated relaxation of coronary arterioles isolated from sexually mature male and female miniature swine. Arterioles (approximately 100-200 microm ID) isolated from the apical region of the heart were cannulated and studied using videodimensional analysis under constant intraluminal pressure. Coronary arterioles from male and female pigs demonstrated similar levels of basal tone and reductions in basal diameter in response to the K(+)-channel blockers 4-aminopyridine (4-AP; 1 mM), tetraethylammonium (1 mM), and glibenclamide (Glib; 10 microM), with 4-AP producing significantly greater constriction than tetraethylammonium or Glib. After endothelin-induced preconstriction, relaxation responses to adenosine were not significantly different between coronary arterioles of male and female pigs. Inhibition of 4-AP-sensitive channels significantly impaired adenosine-mediated relaxation in arterioles from male but not female pigs. However, inhibition of K(+) channels with iberiotoxin (100 nM) or Glib had no effect on adenosine-induced relaxation in either sex. Results obtained in the presence of nitric oxide synthase inhibition suggest a potential interaction of 4-AP-sensitive channels and nitric oxide at low adenosine concentrations. In conclusion, our data indicate that 4-AP-sensitive channels 1) contribute significantly to basal tone in coronary arterioles of both male and female pigs, 2) contribute to adenosine-mediated relaxation in male but not female pigs, and 3) can contribute to adenosine-induced relaxation independent of nitric oxide production in male pigs. These data are consistent with a significant role for voltage-dependent K(+) channels in adenosine-mediated relaxation of coronary arterioles from males.
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Affiliation(s)
- Cristine L Heaps
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, Missouri 65211, USA.
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52
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Shimoda LA, Sylvester JT, Booth GM, Shimoda TH, Meeker S, Undem BJ, Sham JS. Inhibition of voltage-gated K(+) currents by endothelin-1 in human pulmonary arterial myocytes. Am J Physiol Lung Cell Mol Physiol 2001; 281:L1115-22. [PMID: 11597902 DOI: 10.1152/ajplung.2001.281.5.l1115] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent studies demonstrate that endothelin-1 (ET-1) constricts human pulmonary arteries (PA). In this study, we examined possible mechanisms by which ET-1 might constrict human PA. In smooth muscle cells freshly isolated from these arteries, whole cell patch-clamp techniques were used to examine voltage-gated K(+) (K(V)) currents. K(V) currents were isolated by addition of 100 nM charybdotoxin and were identified by current characteristics and inhibition by 4-aminopyridine (10 mM). ET-1 (10(-8) M) caused significant inhibition of K(V) current. Staurosporine (1 nM), a protein kinase C (PKC) inhibitor, abolished the effect of ET-1. Rings of human intrapulmonary arteries (0.8-2 mm OD) were suspended in tissue baths for isometric tension recording. ET-1-induced contraction was maximal at 10(-8) M, equal to that induced by K(V) channel inhibition with 4-aminopyridine, and attenuated by PKC inhibitors. These data suggest that ET-1 constricts human PA, possibly because of myocyte depolarization via PKC-dependent inhibition of K(V). Our results are consistent with data we reported previously in the rat, suggesting similar mechanisms may be operative in both species.
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Affiliation(s)
- L A Shimoda
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland 21224, USA.
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53
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Archer SL, London B, Hampl V, Wu X, Nsair A, Puttagunta L, Hashimoto K, Waite RE, Michelakis ED. Impairment of hypoxic pulmonary vasoconstriction in mice lacking the voltage-gated potassium channel Kv1.5. FASEB J 2001; 15:1801-3. [PMID: 11481235 DOI: 10.1096/fj.00-0649fje] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- S L Archer
- Vascular Biology Group, Department of Medicine, Division of Cardiology, University of Alberta, Alberta, Canada.
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54
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Shimoda LA, Manalo DJ, Sham JS, Semenza GL, Sylvester JT. Partial HIF-1alpha deficiency impairs pulmonary arterial myocyte electrophysiological responses to hypoxia. Am J Physiol Lung Cell Mol Physiol 2001; 281:L202-8. [PMID: 11404263 DOI: 10.1152/ajplung.2001.281.1.l202] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic hypoxia depolarizes and reduces K+ current in pulmonary arterial smooth muscle cells (PASMCs). Our laboratory previously demonstrated that hypoxia-inducible factor-1 (HIF-1) contributed to the development of hypoxic pulmonary hypertension. In this study, electrophysiological parameters were measured in PASMCs isolated from intrapulmonary arteries of mice with one null allele at the Hif1a locus encoding HIF-1alpha [Hif1a(+/-)] and from their wild-type [Hif1a(+/+)] littermates after 3 wk in air or 10% O2. Hematocrit and right ventricular wall and left ventricle plus septum weights were measured. Capacitance, K+ current, and membrane potential were measured with whole cell patch clamp. Similar to our laboratory's previous results, hypoxia-induced right ventricular hypertrophy and polycythemia were blunted in Hif1a(+/-) mice. Hypoxia increased PASMC capacitance in Hif1a(+/+) mice but not in Hif1a(+/-) mice. Chronic hypoxia depolarized and reduced K+ current density in PASMCs from Hif1a(+/+) mice. In PASMCs from hypoxic Hif1a(+/-) mice, no reduction in K+ current density was observed, and depolarization was significantly blunted. Thus partial deficiency of HIF-1alpha is sufficient to impair hypoxia-induced depolarization, reduction of K+ current density, and PASMC hypertrophy.
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Affiliation(s)
- L A Shimoda
- Division of Pulmonary and Critical Care Medicine and Institute of Genetic Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland 21224, USA.
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55
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Michelakis ED, Weir EK, Wu X, Nsair A, Waite R, Hashimoto K, Puttagunta L, Knaus HG, Archer SL. Potassium channels regulate tone in rat pulmonary veins. Am J Physiol Lung Cell Mol Physiol 2001; 280:L1138-47. [PMID: 11350792 DOI: 10.1152/ajplung.2001.280.6.l1138] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Intrapulmonary veins (PVs) contribute to pulmonary vascular resistance, but the mechanisms controlling PV tone are poorly understood. Although smooth muscle cell (SMC) K+ channels regulate tone in most vascular beds, their role in PV tone is unknown. We show that voltage-gated (KV) and inward rectifier (Kir) K+ channels control resting PV tone in the rat. PVs have a coaxial structure, with layers of cardiomyocytes (CMs) arrayed externally around a subendothelial layer of typical SMCs, thus forming spinchterlike structures. PVCMs have both an inward current, inhibited by low-dose Ba2+, and an outward current, inhibited by 4-aminopyridine. In contrast, PVSMCs lack inward currents, and their outward current is inhibited by tetraethylammonium (5 mM) and 4-aminopyridine. Several KV, Kir, and large-conductance Ca2+-sensitive K+channels are present in PVs. Immunohistochemistry showed that Kir channels are present in PVCMs and PV endothelial cells but not in PVSMCs. We conclude that K+ channels are present and functionally important in rat PVs. PVCMs form sphincters rich in Kir channels, which may modulate venous return both physiologically and in disease states including pulmonary edema.
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MESH Headings
- 4-Aminopyridine/pharmacology
- Animals
- Barium/pharmacology
- Cell Separation
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Glyburide/pharmacology
- Immunohistochemistry
- In Vitro Techniques
- Male
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/ultrastructure
- Myocardium/cytology
- Myocardium/metabolism
- Patch-Clamp Techniques
- Peptides/pharmacology
- Potassium Channel Blockers
- Potassium Channels/metabolism
- Potassium Channels, Inwardly Rectifying
- Pulmonary Circulation/physiology
- Pulmonary Veins/cytology
- Pulmonary Veins/metabolism
- Pulmonary Veins/ultrastructure
- Rats
- Rats, Sprague-Dawley
- Tetraethylammonium/pharmacology
- Vascular Resistance/physiology
- Vasoconstriction/drug effects
- Vasoconstriction/physiology
- Vasodilation/drug effects
- Vasodilation/physiology
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Affiliation(s)
- E D Michelakis
- Department of Medicine (Cardiology), University of Alberta, Edmonton, Alberta T6G 2B7, Canada.
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56
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Madden JA. Focus on "Hypoxic constriction of porcine distal pulmonary arteries: endothelium and endothelin dependence". Am J Physiol Lung Cell Mol Physiol 2001; 280:L853-5. [PMID: 11290507 DOI: 10.1152/ajplung.2001.280.5.l853] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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57
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Platoshyn O, Yu Y, Golovina VA, McDaniel SS, Krick S, Li L, Wang JY, Rubin LJ, Yuan JX. Chronic hypoxia decreases K(V) channel expression and function in pulmonary artery myocytes. Am J Physiol Lung Cell Mol Physiol 2001; 280:L801-12. [PMID: 11238022 DOI: 10.1152/ajplung.2001.280.4.l801] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activity of voltage-gated K+ (KV) channels regulates membrane potential (E(m)) and cytosolic free Ca2+ concentration ([Ca2+](cyt)). A rise in ([Ca2+](cyt))in pulmonary artery (PA) smooth muscle cells (SMCs) triggers pulmonary vasoconstriction and stimulates PASMC proliferation. Chronic hypoxia (PO(2) 30-35 mmHg for 60-72 h) decreased mRNA expression of KV channel alpha-subunits (Kv1.1, Kv1.5, Kv2.1, Kv4.3, and Kv9.3) in PASMCs but not in mesenteric artery (MA) SMCs. Consistently, chronic hypoxia attenuated protein expression of Kv1.1, Kv1.5, and Kv2.1; reduced KV current [I(KV)]; caused E(m) depolarization; and increased ([Ca2+](cyt)) in PASMCs but negligibly affected KV channel expression, increased I(KV), and induced hyperpolarization in MASMCs. These results demonstrate that chronic hypoxia selectively downregulates KV channel expression, reduces I(KV), and induces E(m) depolarization in PASMCs. The subsequent rise in ([Ca2+](cyt)) plays a critical role in the development of pulmonary vasoconstriction and medial hypertrophy. The divergent effects of hypoxia on KV channel alpha-subunit mRNA expression in PASMCs and MASMCs may result from different mechanisms involved in the regulation of KV channel gene expression.
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Affiliation(s)
- O Platoshyn
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, UCSD Medical Center, 200 W. Arbor Dr., San Diego, CA 92103-8382, USA
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58
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Shimoda LA, Sham JS, Shimoda TH, Sylvester JT. L-type Ca(2+) channels, resting [Ca(2+)](i), and ET-1-induced responses in chronically hypoxic pulmonary myocytes. Am J Physiol Lung Cell Mol Physiol 2000; 279:L884-94. [PMID: 11053024 DOI: 10.1152/ajplung.2000.279.5.l884] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the lung, chronic hypoxia (CH) causes pulmonary arterial smooth muscle cell (PASMC) depolarization, elevated endothelin-1 (ET-1), and vasoconstriction. We determined whether, during CH, depolarization-driven activation of L-type Ca(2+) channels contributes to 1) maintenance of resting intracellular Ca(2+) concentration ([Ca(2+)](i)), 2) increased [Ca(2+)](i) in response to ET-1 (10(-8) M), and 3) ET-1-induced contraction. Using indo 1 microfluorescence, we determined that resting [Ca(2+)](i) in PASMCs from intrapulmonary arteries of rats exposed to 10% O(2) for 21 days was 293.9 +/- 25.2 nM (vs. 153.6 +/- 28.7 nM in normoxia). Resting [Ca(2+)](i) was decreased after extracellular Ca(2+) removal but not with nifedipine (10(-6) M), an L-type Ca(2+) channel antagonist. After CH, the ET-1-induced increase in [Ca(2+)](i) was reduced and was abolished after extracellular Ca(2+) removal or nifedipine. Removal of extracellular Ca(2+) reduced ET-1-induced tension; however, nifedipine had only a slight effect. These data indicate that maintenance of resting [Ca(2+)](i) in PASMCs from chronically hypoxic rats does not require activation of L-type Ca(2+) channels and suggest that ET-1-induced contraction occurs by a mechanism primarily independent of changes in [Ca(2+)](i).
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Affiliation(s)
- L A Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Johns Hopkins University, Baltimore, Maryland 21224, USA.
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59
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Platoshyn O, Golovina VA, Bailey CL, Limsuwan A, Krick S, Juhaszova M, Seiden JE, Rubin LJ, Yuan JX. Sustained membrane depolarization and pulmonary artery smooth muscle cell proliferation. Am J Physiol Cell Physiol 2000; 279:C1540-9. [PMID: 11029301 DOI: 10.1152/ajpcell.2000.279.5.c1540] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pulmonary vasoconstriction and vascular medial hypertrophy greatly contribute to the elevated pulmonary vascular resistance in patients with pulmonary hypertension. A rise in cytosolic free Ca(2+) ([Ca(2+)](cyt)) in pulmonary artery smooth muscle cells (PASMC) triggers vasoconstriction and stimulates cell growth. Membrane potential (E(m)) regulates [Ca(2+)](cyt) by governing Ca(2+) influx through voltage-dependent Ca(2+) channels. Thus intracellular Ca(2+) may serve as a shared signal transduction element that leads to pulmonary vasoconstriction and vascular remodeling. In PASMC, activity of voltage-gated K(+) (Kv) channels regulates resting E(m). In this study, we investigated whether changes of Kv currents [I(K(V))], E(m), and [Ca(2+)](cyt) affect cell growth by comparing these parameters in proliferating and growth-arrested PASMC. Serum deprivation induced growth arrest of PASMC, whereas chelation of extracellular Ca(2+) abolished PASMC growth. Resting [Ca(2+)](cyt) was significantly higher, and resting E(m) was more depolarized, in proliferating PASMC than in growth-arrested cells. Consistently, whole cell I(K(V)) was significantly attenuated in PASMC during proliferation. Furthermore, E(m) depolarization significantly increased resting [Ca(2+)](cyt) and augmented agonist-mediated rises in [Ca(2+)](cyt) in the absence of extracellular Ca(2+). These results demonstrate that reduced I(K(V)), depolarized E(m), and elevated [Ca(2+)](cyt) may play a critical role in stimulating PASMC proliferation. Pulmonary vascular medial hypertrophy in patients with pulmonary hypertension may be partly caused by a membrane depolarization-mediated increase in [Ca(2+)](cyt) in PASMC.
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Affiliation(s)
- O Platoshyn
- Department of Medicine, University of California School of Medicine, San Diego, California 92103-8382, USA
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60
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Sham JS, Crenshaw BR, Deng LH, Shimoda LA, Sylvester JT. Effects of hypoxia in porcine pulmonary arterial myocytes: roles of K(V) channel and endothelin-1. Am J Physiol Lung Cell Mol Physiol 2000; 279:L262-72. [PMID: 10926549 DOI: 10.1152/ajplung.2000.279.2.l262] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Effects of acute hypoxia on intracellular Ca(2+) concentration ([Ca(2+)](i)) and cell length were recorded simultaneously in proximal and distal pulmonary (PASMCs) and femoral (FASMCs) arterial smooth muscle cells. Reducing PO(2) from normoxia to severe hypoxia (PO(2) < 10 mmHg) caused small but significant decreases in length and a reversible increase in [Ca(2+)](i) in distal PASMCs and a small decrease in length in proximal PASMCs but had no effect in FASMCs, even though all three cell types contracted significantly to vasoactive agonists. Inhibition of voltage-dependent K(+) (K(V)) channel with 4-aminopyridine produced a greater increase in [Ca(2+)](i) in distal than in proximal PASMCs. In distal PASMCs, severe hypoxia caused a slight inhibition of K(V) currents; however, it elicited further contraction in the presence of 4-aminopyridine. Endothelin-1 (10(-10) M), which itself did not alter cell length or [Ca(2+)](i), significantly potentiated the hypoxic contraction. These results suggest that hypoxia only has small direct effects on porcine PASMCs. These effects cannot be fully explained by inhibition of K(V) channels and were greatly enhanced via synergistic interactions with the endothelium-derived factor endothelin-1.
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Affiliation(s)
- J S Sham
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21224, USA.
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61
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Sato K, Morio Y, Morris KG, Rodman DM, McMurtry IF. Mechanism of hypoxic pulmonary vasoconstriction involves ET(A) receptor-mediated inhibition of K(ATP) channel. Am J Physiol Lung Cell Mol Physiol 2000; 278:L434-42. [PMID: 10710514 DOI: 10.1152/ajplung.2000.278.3.l434] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There is controversy on the role of endothelin (ET)-1 in the mechanism of hypoxic pulmonary vasoconstriction (HPV). Although HPV is inhibited by ET-1 subtype A (ET(A))-receptor antagonists in animals, it has been reported that ET(A)-receptor blockade does not affect HPV in isolated lungs. Thus we reassessed the role of ET-1 in HPV in both rats and isolated blood- and physiological salt solution (PSS)-perfused rat lungs. In rats, the ET(A)-receptor antagonist BQ-123 and the nonselective ET(A)- and ET(B)-receptor antagonist PD-145065, but not the ET(B)-receptor antagonist BQ-788, inhibited HPV. Similarly, BQ-123, but not BQ-788, attenuated HPV in blood-perfused lungs. In PSS-perfused lungs, either BQ-123, BQ-788, or the combination of both attenuated HPV equally. Inhibition of HPV by combined BQ-123 and BQ-788 in PSS-perfused lungs was prevented by costimulation with angiotensin II. The ATP-sensitive K(+) (K(ATP))-channel blocker glibenclamide also prevented inhibition of HPV by BQ-123 in both lungs and rats. These results suggest that ET-1 contributes to HPV in both isolated lungs and intact animals through ET(A) receptor-mediated suppression of K(ATP)-channel activity.
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Affiliation(s)
- K Sato
- Cardiovascular Pulmonary Research Laboratory, Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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62
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Shimoda LA, Sylvester JT, Sham JS. Mobilization of intracellular Ca(2+) by endothelin-1 in rat intrapulmonary arterial smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2000; 278:L157-64. [PMID: 10645903 DOI: 10.1152/ajplung.2000.278.1.l157] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endothelin-1 (ET-1) increases intracellular Ca(2+) concentration ([Ca(2+)](i)) in pulmonary arterial smooth muscle cells (PASMCs); however, the mechanisms for Ca(2+) mobilization are not clear. We determined the contributions of extracellular influx and intracellular release to the ET-1-induced Ca(2+) response using Indo 1 fluorescence and electrophysiological techniques. Application of ET-1 (10(-10) to 10(-8) M) to transiently (24-48 h) cultured rat PASMCs caused concentration-dependent increases in [Ca(2+)](i). At 10(-8) M, ET-1 caused a large, transient increase in [Ca(2+)](i) (>1 microM) followed by a sustained elevation in [Ca(2+)](i) (<200 nM). The ET-1-induced increase in [Ca(2+)](i) was attenuated (<80%) by extracellular Ca(2+) removal; by verapamil, a voltage-gated Ca(2+)-channel antagonist; and by ryanodine, an inhibitor of Ca(2+) release from caffeine-sensitive stores. Depleting intracellular stores with thapsigargin abolished the peak in [Ca(2+)](i), but the sustained phase was unaffected. Simultaneously measuring membrane potential and [Ca(2+)](i) indicated that depolarization preceded the rise in [Ca(2+)](i). These results suggest that ET-1 initiates depolarization in PASMCs, leading to Ca(2+) influx through voltage-gated Ca(2+) channels and Ca(2+) release from ryanodine- and inositol 1,4,5-trisphosphate-sensitive stores.
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Affiliation(s)
- L A Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Johns Hopkins University, Baltimore, Maryland 21224, USA.
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