Pituitary sex hormone receptors are functional in murine and human cell lines in the early developmental stage. Western blot analysis of p42/44 MAPK, p38 MAPK and AKT phosphorylation (p-p42/44 MAPK, p-p38 MAPK and p-AKT) upon FSH, LH, and PRL stimulation of the ES-D3, P19, and NTera2 cell lines. Representative results from two independent experiments are shown.