We derive the QCD corrections to the electroweak gauge bosons vacuum
polarization functions at high and zero--momentum transfer in the case of
arbitrary internal quark masses. We then discuss in this general case (i) the
connection between the O(ααS) calculations of the vector bosons
self--energies using dimensional regularization and the one performed via a
dispersive approach and (ii) the QCD corrections to the ρ parameter for a
heavy quark isodoublet.Comment: 14 pages + 2 figures (not included: available by mail from A.
Djouadi), Preprint UdeM-LPN-TH-93-156 and NYU-TH-93/05/0