Mechanism of increased maternal serum total activin A and inhibin A in preeclampsia

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 subset 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 (r(2) =.26, P =.017, and r(2) =.02, P =.44, respectively). Levels of both proteins were negatively correlated to creatinine clearance (r(2) =.29, P <.0001, and r(2) =.15, P =.003, respectively). Placental mRNA expression for both the alpha and betaA 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.