Denison FC et al. - Treatment of third-trimester placenta with 40 nM PK1 induced a rapid phosphorylation of cSrc, EGFR, and ERK1/2. Phosphorylation of ERK1/2 in response to PK1 was dependent on sequential phosphorylation of cSrc and EGFR. PK1 may have a novel role as a mediator of the inflammatory response in placenta.