Quantitation of five forms of high molecular weight angiotensinogen from human placenta

In addition to the well characterized predominant form of plasma angiotensinogen, which will be termed low molecular weight angiotensinogen (LMrA), significant quantities of a high molecular weight angiotensinogen (HMrA) occur in the human pregnant state. HMrA is the predominant form of angiotensinogen in the placenta and amniotic fluid. The ratio of HMrA/LMrA is elevated in approximately half of the women who develop pregnancy induced hypertension (PIH). This report documents a simple two step methodology for the separation and quantitation of different forms of HMrA. The two steps are gel filtration and ion exchange chromatography. The application of this methodology to amniotic fluid and plasma from normotensive pregnant women and extracts of amnion, chorion, and placental tissue has shown five distinct forms in the tissue extracts and amniotic fluid, but only three significant forms in plasma. The elution position of all forms of HMrA are highly reproducible and are the same for each tissue or fluid studied, thus lending support to the concept that the three forms seen in plasma of normotensive pregnant women are the same as three of the forms of HMrA seen in extracts of placental tissue.