  Modifications of the DGMLY relation for calculation of electromagnetic
$\pi$-meson mass difference based on the Chiral Symmetry Restoration phenomenon
at high energies as well as the Operator Product Expansion of quark densities
for vector ($\rho$) and axial-vector ($a_1$) meson fields difference are
proposed. In the calculations higher meson resonances in vector and
axial-vector channels are taken into account. It is shown that the inclusion of
the first $\rho$ and $a_1$ radial excitations improves the results for
electromagnetic $\pi$-meson mass difference as compared with the previous ones.
Estimations on the electromagnetic $\rho$ and $a_1$-meson decay constants and
the constant $L_{10}$ of effective chiral Lagrangian are obtained from the
generalized Weinberg sum rules.
