  We extend a previous work on the intrinsic spectral properties and energetics
of GRBs with known redshift based on 12 BeppoSAX events by including in the
sample a total of 10 more events detected either by BATSE, BeppoSAX or HETE-2.
An indication of a trend of the total isotropic equivalent radiated energy,
E_rad, with redshift is found and, remarkably, the previously found
relationship between the peak energy of the rest-frame nuFnu spectrum, E_p,rest
, and E_rad is confirmed and its significance increased. The implications of
these results are briefly discussed in the framework of standard models for the
prompt emission of GRBs.
