  We have evaluated the Drell-Yan cross section in nuclei paying special
attention to the meson cloud contribution from pion and rho-meson, for which an
accurate calculation using the meson nuclear spectral functions is used.
Similarly, the nucleonic contribution is evaluated in terms of a relativistic
nucleon spectral function. Fair agreement with experiment is found for
different nuclei and the results show a sizeable contribution from the
renormalized meson cloud. In order to reproduce the experiment a novel element
is introduced, consisting of a gradual energy loss of the incoming proton in
its pass through the nucleus which produces a strong A dependence at x_1 large.
