  We investigate effects of nuclear medium on antiquark distribution in nuclei
applying the results of a recently developed relativistically-covariant
self-consistent model for the pion and the isobar. We take into account Fermi
motion including Pauli blocking and binding effects on the nucleons and medium
effects on the isobar and pion leading to modest enhancement of the pion
light-cone-momentum distribution in large nuclei. As a consequence the
Drell-Yan cross-section ratio with respect to the deuteron exceeds one only for
small values of the light-cone momentum.
