Context : The study of the chemical abundances of HII regions in polar ring galaxies and their implications for the evolutionary scenario of these systems has been a step forward both in tracing the formation history of the galaxy and giving hints on the mechanisms at work during the building of disk by cold accretion process .
It ’ s now important to establish whether such results are typical for the class of polar disk galaxies as whole .

Aims : The present work aims at checking the cold accretion of gas through a “ cosmic filament ” as a possible scenario for the formation of the polar structures in UGC7576 and UGC9796 .
If these form by cold accretion , we expect the HII regions abundances and metallicities to be lower than those of same-luminosity spiral disks , with values of the order of Z \sim 1 / 10 Z _ { \odot } , as predicted by cosmological simulations .

Methods : We have used deep long-slit spectra , obtained with DOLORES @ TNG in the optical wavelengths , of the brightest HII regions associated with the polar structures to derive their chemical abundances and star formation rate .
We used the Empirical methods , based on the intensities of easily observable lines , to derive the oxygen abundance 12 + log ( O / H ) of both galaxies .
Such values are compared with those typical for different morphological galaxy types of comparable luminosity .

Results : The average metallicity values for UGC7576 and UGC9796 are Z = 0.4 Z _ { \odot } and Z = 0.1 Z _ { \odot } respectively .
Both values are lower than those measured for ordinary spirals of similar luminosity and UGC7576 presents no metallicity gradient along the polar structure .
These data , toghether with other observed features , available for the two PRGs in previous works , are compared with the predictions of simulations of tidal accretion , cold accretion and merging , to disentangle between these scenarios .

Conclusions :