  The axial exchange current operator that arises from the coupling of the
axial field to the pion and effective scalar field in nuclei is constructed.
The spatial dependence of this exchange current operator may be determined
directly from the nucleon-nucleon interaction. This "$\pi\sigma$"-axial
exchange current contributes about 5\% to the quenching of the nucleon axial
current coupling constant $g_A^{GT}$ in heavy nuclei.
