Biology Reference
In-Depth Information
a
b
125
125
*
**
**
**
100
100
75
75
50
50
25
25
0
0
10
-12
10
-11
Neuropeptide Y (M)
10
-9
10
-10
10
-8
PMA (1
ยต
M
Fig. 9.3
Placental STB TauT activity is inhibited by neuropeptide Y (NPY) and PMA. Effect of
short-term exposure (2 h) to (
a
) NPY (median and interquartile range;
n
= 10) and (
b
) PMA (line
at median) on TauT activity in placental fragments (fmol/mg protein/30 min) expressed as % of
control. **
p
< 0.03; *
p
< 0.05 vs. 100% (control): Wilcoxon signed-rank test
9.4
Discussion
The activity of TauT in the MVM of the human placental STB is important to
achieve a high intracellular taurine concentration and maintain a gradient that
favours taurine efflux towards the fetus. The finding that STB TauT activity and
expression are similar in placentas from the first trimester and at term implies that
taurine delivery to the fetus is important for fetal growth and development through-
out pregnancy.
Maternal obesity and PE are associated with increased risk of poor fetal out-
come, including stillbirth and FGR, which might be related to inadequate transfer of
taurine across the placenta. In support of this we found that STB TauT activity was
inversely related to maternal BMI, recorded at the first antenatal visit, in both the
first trimester and at term. Average TauT activity in women with a BMI >30 was
60-70% lower than their ideal weight (BMI 18.5-24.9) counterparts at both gesta-
tions. Furthermore, STB TauT activity was ~35% lower in placentas of women with
PE (BMI < 30) compared to women having normal pregnancy. This reduction in
TauT activity could predispose to FGR in these pregnancy conditions but is unlikely
to be singularly responsible, as most of the babies born to the women studied were
appropriately grown for gestational age.
A reduction in MVM STB TauT activity will lower intracellular taurine in the
absence of compensatory changes in taurine efflux. Placental taurine, measured
by chromatography, was found to be lower in infants with low birth weight com-
pared to normal (Ghisolfi et al.
1989
) and in preliminary studies (Hirst et al.
2012
) we showed that the accumulation of radiolabelled taurine in STB at steady
state was lower in PE than in normal pregnancy. In addition to restricting taurine
efflux to the fetus, a reduction in intracellular taurine has implications for the
maintenance of STB. STB is a unique epithelium, being renewed during preg-
nancy by a process of cellular turnover involving proliferation of the underlying
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