Our strategy was to manipulate mTOR signaling in vivo, then characterize the transcriptome and translating mRNA in liver tissue. In adult rats, we used the non-proliferative growth model of refeeding after a period of fasting, and the proliferative model of liver regeneration following partial hepatectomy. We also studied livers from pre-term fetal rats (embryonic day 19-20) in which fetal hepatocytes are asynchronously proliferating. All three models employed rapamycin to inhibit mTOR signaling. Overall design: For the non-proliferative growth model, adult rats were fasted 48hr followed by an IP injection of DMSO (n=3) or rapamycin (250ug/100g body wt) (n=3). Sixty minutes later rats were refed ad libitum for 3hr before sacrifice. For the proliferative model, one hour preceding a 2/3 partial hepatectomy (PHep) rats were injected IP with DMSO (n=3) or rapamycin (250ug/100g body wt.) (n=3). Twenty-four hours following PHep, animals were sacrificed. Fetal rats were injected with DMSO (n=4) or 50ug of rapamycin (n=4) on day E19 of gestation. Twenty four hours later (E20), the fetal rats were delivered and livers were removed. All livers were flash frozen in liquid nitrogen. RNA was extracted from polysomes that were generated using sucrose density fraction, as well as total liver. RNA was hybridized to Affymetrix Genechip Rat Gene 1.0 ST Arrays.