  The data of J/psi suppression at large x_F in pA collisions are used to infer
the existence of gluon depletion as the projectile proton traverses the
nucleus. The modification of the gluon distribution is studied by use of a
convolution equation whose non-perturbative splitting function is determined
phenomenologically. The depletion factor at x_1=0.8 is found to be about 25% at
A=100.
