  Motivated by our earlier findings of sensitive quark-flavor dependence of QCD
topological susceptibility on products of current quark masses and
corresponding condensates, we allow the breaking of isospin symmetry. For the
purpose of future investigations of U_A(1) symmetry breaking and restoration at
T > 0, we perform (at T = 0) refitting of the quark-mass parameters of a
phenomenologically successful effective model of low-energy QCD. It belongs to
the class of separable-interaction models within the Dyson-Schwinger approach
to the quark-antiquark substructure of mesons.
