Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
retain [rɪˈteɪn] vt (keep) сохраня́ть (сохрани́ть perf), уде́рживать (удержа́ть perf)
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.