  Due to the internal structure of the nucleon, we should expect, in general,
that the effective meson nucleon parameters may change in nuclear medium. We
study such changes by using a chiral confining model of the nucleon. We use
density-dependent masses for all mesons except the pion. Within a
Dirac-Brueckner analysis, based on the relativistic covariant structure of the
NN amplitude, we show that the effect of such a density dependence in the NN
interaction on the saturation properties of nuclear matter, while not large, is
quite significant. Due to the density dependence of the $g_{\sigma NN}$, as
predicted by the chiral confining model, we find, in particular, a looping
behavior of the binding energy at saturation as a function of the saturation
density. A simple model is described, which exhibits looping and which is shown
to be mainly caused by the presence of a peak in the density dependence of the
medium modified $\sigma N$ coupling constant at low density.
  The effect of density dependence of the coupling constants and the meson
masses tends to improve the results for $E/A$ and density of nuclear matter at
saturation. From the present study we see that the relationship between binding
energy and saturation density may not be as universal as found in
nonrelativistic studies and that more model dependence is exhibited once medium
modifications of the basic nuclear interactions are considered.
