Mechanism of Increased Maternal Serum Total Activin A and Inhibin A in Preeclampsia

Abstract

Objective: To determine whether increased levels of maternal serum total activin A and inhibin A in preeclampsia are related to total blood volume, urinary clearance, or placental production.

Study Design: Activin A and inhibin A levels were measured in preeclamptic subjects and matched normotensive gravidas. In a subset of preeclamptic subjects (n = 21) and controls (n = 30), we performed blood volume studies. In an overlapping subject of preeclamptic subjects (n = 56), creatinine clearance results were available. Placental tissue was obtained from six preeclamptics and matched normotensive gravida for analysis of activin A and inhibin A mRNA expression.

Results: Maternal serum levels of inhibin A but not activin A were significantly negatively correlated with blood volume in preeclampsia (r² = .26, P = 0.17, and r² = .02, P = .44, respectively). Levels of both proteins were negatively correlated to creatinine clearance (r² = .29, P < .0001, and r² = .15, P = .003, respectively). Placental mRNA expression for both the α and βA subunits was increased in preeclampsia (P = .038 and .049, respectively).

Conclusion: Although placental mRNA expression of the subunits for both analytes is increased in preeclampsia, the increased levels of activin A appear to be more specifically a reflection of increased placental production than do the increased levels of inhibin A.