Characterization of nitric oxide synthase in the opossum esophagus

Joseph A Murray, Eugene D. Clark

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Background/Aims: Nitric oxide mediates the nonadrenergic, noncholinergic neural control of esophageal motor function. The purpose of this study was to characterize the NO synthase found in the muscularis propria of the opossum esophagus and determine its distribution along the esophagus. Methods: Esophageal muscle was homogenized in HEPES buffer and ultracentrifuged. The supernatant was exposed to [3H]l-arginine. The [3H]l-citrulline produced by NO synthase was separated from [3H]l-arginine with a Dowex AG 50 W-X8 column (Biorad, Hercules, CA). Assays were performed in the presence and absence of Ca2+ or reduced nicotinamide adenine dinucleotide phosphate (NADPH). The distribution of NO synthase activity along the esophagus was determined. Results: The apparent Michaelis constant and maximum velocity of NO synthase were 7.5 ± 1.4 μmol/L l-arginine and 76.0 ± 17.3 pmol·mg protein-1 ·min-1, respectively. The enzyme required both Ca2+ and NADPH for activity. Smooth muscle tissue from the lower esophageal sphincter and the esophageal body 1-2 cm or 5-6 cm above the lower esophageal sphincter differed little in enzymatic activity, ranging from 0.97 to 1.27 pmol·mg wet wt-1·min-1. Striated muscle had less activity with 0.40 pmol·mg wet wt-1·min-1. Conclusions: These data indicate the presence of a constitutive NO synthase in the esophagus of the opossum.

Original languageEnglish (US)
Pages (from-to)1444-1450
Number of pages7
JournalGastroenterology
Volume106
Issue number6
StatePublished - 1994
Externally publishedYes

Fingerprint

Opossums
Nitric Oxide Synthase
Esophagus
Arginine
Lower Esophageal Sphincter
NADP
HEPES
Muscles
Citrulline
Striated Muscle
Smooth Muscle
Buffers
Nitric Oxide
Enzymes
Proteins

ASJC Scopus subject areas

  • Gastroenterology

Cite this

Characterization of nitric oxide synthase in the opossum esophagus. / Murray, Joseph A; Clark, Eugene D.

In: Gastroenterology, Vol. 106, No. 6, 1994, p. 1444-1450.

Research output: Contribution to journalArticle

Murray, Joseph A ; Clark, Eugene D. / Characterization of nitric oxide synthase in the opossum esophagus. In: Gastroenterology. 1994 ; Vol. 106, No. 6. pp. 1444-1450.
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