Placental mammalian target of rapamycin and related signaling pathways in an ovine model of intrauterine growth restriction.

Abstract

Both phosphorylated (p) mammalian target of rapamycin (mTOR) and protein S6 kinase 1 (p70S6K) are known to regulate protein synthesis and are affected during intrauterine growth restriction (IUGR). We studied the mTOR pathway during hyperthermia (HT)-induced IUGR in sheep. Beginning at 40 days gestational age, 4 ewes were exposed to HT for 55 days and 4 were exposed for 80 days to induce IUGR. Western blot analyses were performed for mTOR, p70S6K, 4E-binding protein 1, extracellularly regulated kinase (ERK), and AKT. HT animals showed: smaller fetuses and placentas near term; reduced placental weight at midgestation; increased p-mTOR, p-ERK, and p-AKT; decreased p70S6K in the near-term cotyledons; decreased p- p70S6K; and increased p-ERK in the caruncles (maternal) near term. Near-term IUGR ovine cotyledons showed up-regulation of p-mTOR, whereas p70S6K was decreased. This suggests that the changes in placental mTOR signaling proteins could be driven by the fetal stress observed near term in this model of IUGR.