  We consider the Einstein-Maxwell system of equations in the context of
isotropic coordinates for matter distributions with anisotropy in the presence
of an electric field. We assume a polytropic equation of state for the matter
configuration. New classes of exact solutions are generated for different
polytropic indices. The model is well behaved and we can regain masses of
several observed objects, in particular we obtain the mass of the star PSR
J1903+327.
