We analyse the proton-induced Drell-Yan production in both the flavour-asymmetry and isospin-breaking explanations for the violation of the Gottfried sum rule. Consequences from three different forms of corrections to the flavour and isospin symmetric parton distributions are examined, It is found that the calculated results are sensitive to the choice of parameters and parton distributions, and to the ways in which the corrections are introduced. All three forms of corrections could be consistent with the recent Fermilab Experiment E772 data for the ratio of cross section R= sigma _W/ sigma _IS and for the shape of the differential cross section m³d² sigma /dx_Fdm for ²H.