Problem setting environmental variables for postgresql or plpythonu

I''m hoping someone can help me out. I'm wanting to run GRASS GIS from within a plpythonu function block. But to run GRASS GIS externally, the following environmental variables need to be available to the Postgresql server...

GISBASE='/usr/local/grass-6.4.3svn'
PATH='$PATH:$GISBASE/bin:$GISBASE/scripts:$GISBASE/lib'
PYTHONPATH='${PYTHONPATH}:$GISBASE/etc/python/'
PYTHONPATH='${PYTHONPATH}:$GISBASE/etc/python/grass'
PYTHONPATH='${PYTHONPATH}:$GISBASE/etc/python/grass/script'
LD_LIBRARY_PATH='$LD_LIBRARY_PATH:$GISBASE/lib'
GIS_LOCK='$$'
GISRC='$HOME/.grassrc6'

Reference: http://grass.osgeo.org/wiki/GRASS_and_Python

So far I've added these variables to /etc/bash.bashrc
which makes them available to the postgres user (but not the server or pl/python).

And I've had no success adding them to...
/etc/postgresql/9.1/main/environment
#Shell commands are not evaluated.

Any suggestions would be appreciated...

Thanks
Mark