Nitric oxide synthase activity in human trophoblast, term placenta and pregnant myometrium

J Al-Hijji,Ellika Andolf,Satish Batra,Ricardo Laurini

doi:10.1186/1477-7827-1-51

J Al-Hijji, Ellika Andolf + Show 2 more

Open Access

https://doi.org/10.1186/1477-7827-1-51

Copy DOI

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.

Highlights

Nitric oxide (NO) is a multifunctional signal and important modulator of cellular responses in a variety of tissues including those involved in human reproduction
NO is generated from L-arginine by the catalytic action of the enzyme, nitric oxide synthase (NOS)
The activity of NOS in particulate fractions from both preparations was considerably higher than the cytosolic fractions

Summary

Introduction

Nitric oxide (NO) is a multifunctional signal and important modulator of cellular responses in a variety of tissues including those involved in human reproduction. NO is generated from L-arginine by the catalytic action of the enzyme, nitric oxide synthase (NOS). Three different isoform of NOS have been identified, cloned and characterised. While two of the three (type I or neuronal and III or endothelial) are constitutively expressed in a variety of tissues, the expression of the third isoform NO is known to have a powerful vasodilatory effect in resistance vessels throughout the body. This action is, mediated by locally produced NO and in most instances by the subsequently generated second messenger guanosine 3–5 cyclic monophosphate (cGMP)

Methods

Results

Conclusion