Nitric oxide synthase activity in human trophoblast, term placenta and pregnant myometrium |
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Authors: | J Al-Hijji Ellika Andolf Ricardo Laurini and Satish Batra |
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Institution: | (1) Department of Obstetrics and Gynecology, University Hospital, S-281 85 Lund, Sweden |
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Abstract: | To investigate the possible role of nitric oxide (NO) produced locally or intramurally in the quiescence of the pregnant myometrium,
nitric oxide synthase (NOS) activity was measured in samples from first trimester (villous, and non villous-trophoblast),
term placenta and pregnant myometrium. Trophoblast tissue was obtained from psychosocial termination of pregnancy (9 – 12
weeks' gestation) whereas placenta and myometrium, from the same patient, at deliveries by Caesarean section. NOS activity
was measured in both cytosolic and particulate fractions by the formation of 14C-citrulline from 14C-arginine. Western immunoblotting was used to identify the endothelial NOS (eNOS) and neuronal (nNOS) isoforms. The activity
of NOS in particulate fractions from all preparations was considerably higher than the cytosolic fractions. Activity in all
fractions except the myometrium was highly Ca-dependent. More than 50% of particulate NOS from the myometrium was Ca-independent.
NOS activity was highest in the villous trophoblast and there was a significant difference between the villous and non-villous
trophoblast. In placenta and myometrium, NOS was 2–4 fold and 20–28-fold lower than the villous trophoblast, respectively.
Western blot analysis showed clearly eNOS in the particulate fraction and a weak eNOS band in the cytosolic fractions, whereas
nNOS was not detectable in any of the fractions. In view of the marginal activity of NOS in the myometrium, NO produced by
the trophoblast and placenta could play a significant role in maintaining uterine quiescence by paracrine effect. |
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