Tetrahydrobiopterin (BH4) and superoxide dismutase (SOD) synergistically augment endothelium-dependent relaxations in canine middle cerebral artery

M. Tsutsui, S. Milstien, Zvonimir S Katusic

Research output: Contribution to journalArticle

Abstract

BH4 is an essential cofactor required for activation of nitric oxide synthase. The present study was designed to determine the effect of an increase in endogenous BH4 on endothelium-dependent relaxations in canine middle cerebral arteries. Segments of the isolated arteries were incubated (24 h at 37°C) in minimum essential medium in the presence and in the absence of a tetrahydrobiopterin precursor, sepiapterin (10-4M), and/or SOD (150 U/ml). The arteries were suspended for isometric tension recording. BH4 levels were assayed by high performance liquid chromatography. Levels of cGMP were measured by radioimmunoassay. All experiments were performed in the presence of indomethacin (10-5 M). Incubation with sepiapterin markedly increased intracellular biopterin levels (Control, 363±273 vs. Sepiapterin, 118960±27151 pmol/g wet weight, n=5, P<0.01). In the sepiapterin-treated arteries, endothelium-dependent relaxations to calcium ionophore A23187 and intracellular cGMP levels were significantly decreased. SOD alone did not affect those responses. However, incubation with SOD plus sepiapterin significantly augmented the endothelium-dependent relaxations as well as the cGMP production. This augmentation was observed only in rings with (but not without) endothelium. The removal of Ca2+ from the medium abolished the synergistic effect of BH4 and SOD. These results demonstrate that in the presence of SOD, increased availability of endogenous BH4 may activate endothelial nitric oxide synthase.

Original languageEnglish (US)
JournalFASEB Journal
Volume10
Issue number3
StatePublished - 1996

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Middle Cerebral Artery
endothelium
arteries
Superoxide Dismutase
Endothelium
Canidae
superoxide dismutase
dogs
Arteries
biopterin
Biopterin
calcium
indomethacin
Calcium Ionophores
Nitric Oxide Synthase Type III
Level control
Calcimycin
ionophores
High performance liquid chromatography
nitric oxide synthase

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Cell Biology

Cite this

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abstract = "BH4 is an essential cofactor required for activation of nitric oxide synthase. The present study was designed to determine the effect of an increase in endogenous BH4 on endothelium-dependent relaxations in canine middle cerebral arteries. Segments of the isolated arteries were incubated (24 h at 37°C) in minimum essential medium in the presence and in the absence of a tetrahydrobiopterin precursor, sepiapterin (10-4M), and/or SOD (150 U/ml). The arteries were suspended for isometric tension recording. BH4 levels were assayed by high performance liquid chromatography. Levels of cGMP were measured by radioimmunoassay. All experiments were performed in the presence of indomethacin (10-5 M). Incubation with sepiapterin markedly increased intracellular biopterin levels (Control, 363±273 vs. Sepiapterin, 118960±27151 pmol/g wet weight, n=5, P<0.01). In the sepiapterin-treated arteries, endothelium-dependent relaxations to calcium ionophore A23187 and intracellular cGMP levels were significantly decreased. SOD alone did not affect those responses. However, incubation with SOD plus sepiapterin significantly augmented the endothelium-dependent relaxations as well as the cGMP production. This augmentation was observed only in rings with (but not without) endothelium. The removal of Ca2+ from the medium abolished the synergistic effect of BH4 and SOD. These results demonstrate that in the presence of SOD, increased availability of endogenous BH4 may activate endothelial nitric oxide synthase.",
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T1 - Tetrahydrobiopterin (BH4) and superoxide dismutase (SOD) synergistically augment endothelium-dependent relaxations in canine middle cerebral artery

AU - Tsutsui, M.

AU - Milstien, S.

AU - Katusic, Zvonimir S

PY - 1996

Y1 - 1996

N2 - BH4 is an essential cofactor required for activation of nitric oxide synthase. The present study was designed to determine the effect of an increase in endogenous BH4 on endothelium-dependent relaxations in canine middle cerebral arteries. Segments of the isolated arteries were incubated (24 h at 37°C) in minimum essential medium in the presence and in the absence of a tetrahydrobiopterin precursor, sepiapterin (10-4M), and/or SOD (150 U/ml). The arteries were suspended for isometric tension recording. BH4 levels were assayed by high performance liquid chromatography. Levels of cGMP were measured by radioimmunoassay. All experiments were performed in the presence of indomethacin (10-5 M). Incubation with sepiapterin markedly increased intracellular biopterin levels (Control, 363±273 vs. Sepiapterin, 118960±27151 pmol/g wet weight, n=5, P<0.01). In the sepiapterin-treated arteries, endothelium-dependent relaxations to calcium ionophore A23187 and intracellular cGMP levels were significantly decreased. SOD alone did not affect those responses. However, incubation with SOD plus sepiapterin significantly augmented the endothelium-dependent relaxations as well as the cGMP production. This augmentation was observed only in rings with (but not without) endothelium. The removal of Ca2+ from the medium abolished the synergistic effect of BH4 and SOD. These results demonstrate that in the presence of SOD, increased availability of endogenous BH4 may activate endothelial nitric oxide synthase.

AB - BH4 is an essential cofactor required for activation of nitric oxide synthase. The present study was designed to determine the effect of an increase in endogenous BH4 on endothelium-dependent relaxations in canine middle cerebral arteries. Segments of the isolated arteries were incubated (24 h at 37°C) in minimum essential medium in the presence and in the absence of a tetrahydrobiopterin precursor, sepiapterin (10-4M), and/or SOD (150 U/ml). The arteries were suspended for isometric tension recording. BH4 levels were assayed by high performance liquid chromatography. Levels of cGMP were measured by radioimmunoassay. All experiments were performed in the presence of indomethacin (10-5 M). Incubation with sepiapterin markedly increased intracellular biopterin levels (Control, 363±273 vs. Sepiapterin, 118960±27151 pmol/g wet weight, n=5, P<0.01). In the sepiapterin-treated arteries, endothelium-dependent relaxations to calcium ionophore A23187 and intracellular cGMP levels were significantly decreased. SOD alone did not affect those responses. However, incubation with SOD plus sepiapterin significantly augmented the endothelium-dependent relaxations as well as the cGMP production. This augmentation was observed only in rings with (but not without) endothelium. The removal of Ca2+ from the medium abolished the synergistic effect of BH4 and SOD. These results demonstrate that in the presence of SOD, increased availability of endogenous BH4 may activate endothelial nitric oxide synthase.

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