title: Expression of nitric oxide synthase isoforms in pregnant human myometrium.
abstract: 1. Endogenous nitric oxide has been proposed to play a role in the control of myometrial contractility in pregnancy. In this study, the expression, localisation and regulation of nitric oxide synthase (NOS) isoforms have been examined in human pregnant myometrium and cultured human myometrial smooth muscle cells, by immunoblotting, immunohistochemistry and reverse transcription-polymerase chain reaction. 2. Immunoblotting of extracts from freshly isolated myometrial tissue, affinity-enriched for NOS proteins by precipitation with ADP-sepharose, revealed expression of endothelial NOS (eNOS or NOS3) in tissues from preterm, term non-labour and active labour at term. Inducible NOS (iNOS or NOS2) and neuronal NOS (nNOS or NOS1) proteins were not detected at any stage of pregnancy. 3. Immunohistochemical detection showed that expression of eNOS protein was restricted to the endothelium of the myometrial vasculature, with no staining detected in myometrial smooth muscle cells. 4. Messenger RNA for all three NOS isoforms was detected, although iNOS and nNOS mRNAs were detectable only with high cycle number, implying a low copy number. 5. NOS isoforms were not detectable in human myometrial smooth muscle cells cultured from term non-labour pregnancies. Cytokine stimulation of cultured myometrial cells did not induce iNOS expression or nitrite accumulation in the culture medium, although both iNOS protein and nitrite release were detected in the human pulmonary epithelial cell line A549. 6. Levels of eNOS protein and of NOS mRNA expression were not correlated with gestational stage, suggesting that endogenously produced NO is not likely to be a modulator of myometrial tone during human pregnancy.
authors.affiliation: Centre for Cardiovascular Biology and Medicine, GKT Schools of Biomedical Sciences and Medicine, King's College London, UK.
authors.forename: S R
authors.initials: SR
authors.lastname: Bartlett
authors.forename: P R
authors.initials: PR
authors.lastname: Bennett
authors.forename: J S
authors.initials: JS
authors.lastname: Campa
authors.forename: W J
authors.initials: WJ
authors.lastname: Dennes
authors.forename: D M
authors.initials: DM
authors.lastname: Slater
authors.forename: G E
authors.initials: GE
authors.lastname: Mann
authors.forename: L
authors.initials: L
authors.lastname: Poston
authors.forename: R
authors.initials: R
authors.lastname: Poston
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology; D005260:Female; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000096:biosynthesis; D007743:Labor, Obstetric / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology; D009130:Muscle, Smooth / Q000201:enzymology / Q000648:ultrastructure; D009215:Myometrium / Q000201:enzymology* / Q000648:ultrastructure; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D009573:Nitrites / Q000378:metabolism; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D016207:Cytokines; D007527:Isoenzymes; D008070:Lipopolysaccharides; D009573:Nitrites; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase