Detection of phosphorylated PR-A and PR-B with P9007-31J. Human T47D cells were either untreated or treated for 60 minutes with 100 nM of the synthetic progestin promegestone. Total cell lysates in gel sample buffer were resolved by SDS-PAGE, transferred to an Immobilon-P membrane and immunoblotted with 0.5 μg/mL rabbit anti-Phospho-PR (S294), as described in Protocols for Immunoblotting.