  The $Q^2$ dependence of the ratios of nuclear structure functions $F_2^A$ is
studied by performing QCD evolution of nuclear parton distribution functions.
The log $Q^2$ slope of these ratios is very sensitive to the nuclear gluon
distribution function. Taking different parametrizations, we show that the NMC
data on the $Q^2$ dependence of $F_2^{\rm Sn}/F_2^{\rm C}$ rule out the case
where nuclear shadowing (suppression) of gluons at $x\sim 0.01$ is much larger
than the shadowing observed in the ratio $F_2^A/F_2^{\rm D}$. We also take into
account modifications to the DGLAP evolution by including gluon fusion terms
and see that the effect is small at present energies, and, in any case, a
strong gluon shadowing is not favored. The region studied ($x \sim 0.01$) is
the most relevant for RHIC multiplicities.
