hCG induces the synthesis and secretion of P
by hESCs. (a) Total RNA isolated from hESCs was amplified by RT-PCR by using two pairs of sequence-specific primers for StAR. The expected 404-bp and 408-bp cDNA fragments were detected (left panel). Equal amounts of protein from cell lysates of hESCs, EBs and rosettes were analyzed with immunoblot with an anti-human StAR polyclonal antibody  (right). Molecular-weight markers are shown on the left. (b) The concentration of P4 secreted into the media from hESCs treated ± hCG (500 mIU/ml) for 6 days. Results are expressed as micrograms P4 per microgram cellular protein, mean ± SEM, n = 3; *P < 0.001.