  There exist isolated elliptical galaxies, whose dynamics can be modelled
without resorting to dark matter or MOND, e.g. NGC 7507. The isolated
elliptical NGC 5812 is another object to investigate a possible role of
isolation. We use globular clusters (GCs) and the galaxy light itself as
dynamical tracers to constrain its mass profile. We employ Gemini/GMOS mask
spectroscopy, apply the GMOS reduction procedures provided within IRAF, measure
GC velocities by cross correlation methods and extract the line-of-sight
kinematics of galaxy spectra using the tool pPXF. We identify 28 GCs with an
outermost galactocentric distance of 20 kpc, for which velocities could be
obtained. Furthermore, 16 spectra of the integrated galaxy light out to 6 kpc
have been used to model the central kinematics. These spectra provide evidence
for a disturbed velocity field. We construct spherical Jeans models for the
galaxy light and apply tracer mass estimators for the globular clusters. With
the assumptions inherent to the mass estimators, MOND is compatible with the
mass out to 20 kpc. However, a dark matter free galaxy is not excluded. We find
one globular cluster with an estimated mass of 1.6x10**7 solar masses, the
first Ultra Compact Dwarf in an isolated elliptical. We put NGC 5812 into the
general context of dark matter or alternative ideas in elliptical galaxies. The
case for a MONDian phenomenology also among early-type galaxies has become so
strong that deviating cases appear astrophysically more interesting than
agreements. The baryonic Tully Fisher relation (BTFR) as predicted by MOND is
observed in some samples of early-type galaxies, in others not. However, in
cases of galaxies that deviate from the MONDian prediction, data quality and
data completeness are often problematic. (abridged)
