The A dependences of the cross sections for heavy-quark production, as
well as those for the production of Drell-Yan lepton pairs, are compu
ted with allowance for distinctions between parton distributions in fr
ee and bound nucleons. This is done for both proton-nucleus and nucleu
s-nucleus collisions. If the resulting cross sections are parametrized
as sigma similar to A(alpha), the values of alpha for heavy-quark pro
duction at moderately low energies prove to be slightly greater than u
nity. With increasing initial energy, the exponent alpha decreases mon
otonically down to values that are less than unity. It is also shown t
hat alpha is a function of the Feynman variable x(F) of the product <Q
(Q)over bar> or l(+)l(-) pair. The sensitivity of these results to the
set of parton distributions that is used in the present study is disc
ussed.