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be a measure of TauT activity in STB. To study the effect of NPY/PMA on TauT
activity, placental fragments were incubated for 2 h (37°C) in NPY (5pM-5nM) or
PMA (1 mM) prior to measurement of 3 H-taurine uptake. TauT activity in treated
tissue was expressed relative to the corresponding untreated control and analysed
using a Wilcoxon Signed Rank test where p < 0.05 was considered signi fi cant.
9.3
Results
9.3.1
Placental TauT Expression and Activity in Normal
Pregnancy
There were no significant differences in SLC6A6 mRNA expression between 6-9
weeks and 10-13 weeks gestation, or between these gestations and term (Fig. 9.1a ).
Western blot analysis of first trimester and term placental homogenates (Fig. 9.1b )
revealed a single immunoreactive signal at ~70 kDa in all samples, which corre-
sponds to the predicted size of TauT (Ramamoorthy et al. 1994 ) . Pre-absorption of
the antibody with 5× peptide abolished this signal (data not shown), confirming
antibody specificity for TauT. Densitometric analysis revealed no differences in
either TauT (Fig. 9.1b ) or b-actin (used to indicate protein loading; data not shown)
expression in placentas from the first trimester compared to term. Na + -dependent
3 H-taurine uptake (Fig. 9.1c ), representing TauT-specific activity, by first trimester
and term placental villous fragments was linear over 5-30 min ( p < 0.005 for both;
least squares linear regression) indicating that uptake was at initial rate. TauT activ-
ity in the first trimester did not differ to that at term (Fig. 9.1c ).
9.3.2
Placental STB TauT Activity in Maternal Obesity and PE
In both the first trimester and at term, there was significant negative relationship between
STB TauT activity and maternal BMI (Fig. 9.2a ). Comparison of placental TauT activity
in obese women (BMI >30) and ideal weight women (BMI 18-24.9) revealed a
significant difference at both gestations ( p < 0.05, MannWhitney- U test). TauT activity
was also significantly lower in PE (ideal weight) than normal pregnancy (Fig. 9.2b ).
9.3.3
Placental TauT Activity Following Exposure
to Neuropeptide Y
Figure 9.3a shows concentration-dependent inhibition of TauT activity (30 min) in
term villous fragments by NPY (50 pM-50 nM; 2 h). TauT activity was reduced to
a similar extent by the PKC activator PMA (1 mM) (Fig. 9.3b ).
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