Expression and activation of Akt/protein kinase B in sexually immature and mature rat uterus

This study investigated the expression and activation of Akt/PKB in developing and adult rat uterus. Expression of Akt was observed in uteri from adult ovariectomized and 7–35-day-old rats and no changes were observed in response to in vivo estradiol treatment (1–100 μg/100 g b.w.). To examine the mechanisms of PKB/Akt activation, phosphorylation at Thr³⁰⁸ and Ser⁴⁷³ regulatory sites were studied in uteri. Akt was constitutively phosphorylated on Ser⁴⁷³ residue in the untreated, control uteri, while phosphorylation of Thr³⁰⁸ was observed only after estradiol 17β (E2) treatment. The effects of E2 treatment were age dependent, no response was induced in 11-day-old uteri, while in 28 days and older rats the activation of Akt at both regulatory sites, Ser⁴⁷³ and Thr³⁰⁸, increased, the first response was detected 2 h after treatment, reaching the highest rate at 6 h. The rate of phosphorylation was stronger at Ser⁴⁷³ residue. The results suggest that the regulation of Akt activation at two regulatory sites in rat uteri are different, phosphorylation of Thr³⁰⁸ seems to be entirely estrogen dependent, while the phosphorylation of Ser⁴⁷³ is regulated by other factors as well as estrogen.