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J.Health Sci., 50(6), 689-692, 2004
Region- and Isoform-Specific Expression of Hydroxysteroid
Sulfotransferases
in Rat Brain
Mikiko Shimizu,a Yukiko
Nakano,a
Tomoko Yamasaki,a Tetsuya
Kimoto,b
Suguru Kawato,b and Hiro-omi
Tamura*, a
aKyoritsu University of Pharmacy, 1-5-30, Shibakoen,
Minatoku, Tokyo 105-8512, Japan and bDepartment of
Biophysics and Life Sciences, Graduate School of Arts and Sciences,
University of Tokyo at Komaba, 3-8-1 Komaba, Meguro,
Tokyo 153-8902, Japan
Hydroxysteroid sulfotransferase (HS-ST) is thought to be a key enzyme in the synthesis of
neurosteroid sulfates, which are known to act as potent
regulators of neuronal activity within the brain. In rat liver,
three isoforms of HS-ST (ST2A1, ST2A2 and ST2A5) have now been identified and to further elucidate the
precise contribution of each of these variants in
neurosteroid sulfation in rat brain, we analyzed the
expression of their transcripts in different brain
regions using isoform-specific RT-PCR. The expression
of ST2A1 was found exclusively in the olfactory bulb
and ST2A2 expression levels were most abundant in
the hippocampus, but no ST2A5 expression was detectable in any brain region. We then measured the
HS-ST activity in these same regions and detected low
but significant activity levels in the olfactory bulb and
hippocampus, but less activity in the cortex. These
activity levels were found to correlate with the mRNA
levels of the HS-ST isoforms. Our findings will
further our understanding of the physiological role of
HS-ST enzymes within the brain, particularly how they
affect neurosteroid metabolism and modulate neuronal
activity.
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