5HT and 5HTP production in PC12 cells. PC12 cells were transfected
with wild-type HA-TPH2, HA-TPH2 S19A, or HA-TPH2
S19D, and 48–72 h post-transfection, 5HT was measured, or cells were
treated with 100 μm NSD-1015 to block the activity of AADC and
either 2.5 μm forskolin or an equal volume of DMSO for 16 h to
assess accumulation of 5HTP. A, 5HT content in untreated cells was
measured by HPLC and normalized to the endogenously produced dopamine content
produced by the cells to control for differences in the number of cells used
to produce the lysates. ‡, p < 0.05 compared with HA-TPH2;
†, p < 0.05 compared with S19A. B, similar to the
results in A, 5HTP content was measured in cells transfected with
each of the three constructs and treated with 100 μm NSD-1015
for 16 h to block AADC as described above (*, p < 0.001
compared with HA-TPH2). 5HTP accumulation was also assessed in cells treated
with forskolin and NSD-1015 for 16 h (**, p < 0.001
compared with untreated controls; %, p < 0.05 compared with
HA-TPH2 + forskolin; #, p < 0.001 compared with HA-TPH2 +
forskolin). 5HTP content in the cell lysates was also normalized to the
endogenously produced dopamine content produced by the cells before the
initiation of treatment to control for differences in cell number used to
produce the lysates. Data are means ± S.E. (n = 4).