[en] Full text. A new expression for the energy density of baryons or quarks for relativistic models for nuclear matter is proposed such that it incorporates further interaction effects with the vector fields, usually described by the solution of the Euler-Lagrange equations for the mean field. Although the calculation is based in a solution of the Dirac equation it considers the effect of the component of the classical vector meson V₀. A different vector meson profile is also used and compared to the mean field. As one outcome it is seen that the density dependence of the vector meson solutions (not only the usual V₀ but also the ones for the rho meson mean field) can contribute for the stiffness of the e.o.s. The neutron - proton asymmetric nuclear matter is also discussed and the value of the symmetry energy coefficient is calculated. The dependence of the symmetry energy on the density is also calculated with some preliminary results. A corresponding calculation for the density of baryons is also presented. (author)