Dual natriuretic peptide response to volume load in the fetal circulation.

OBJECTIVE To measure atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in control fetuses and fetuses with Rhesus isoimmunisation before and after intravascular transfusion. The current study was designed to investigate the response of ANP and BNP to cardiac short-term and long-term volume load in the human fetus. METHODS Fetal blood samples were collected from 18 human fetuses (nine controls, nine anemic fetuses with Rhesus isoimmunisation before and after intravascular transfusion). Fetal ANP and BNP concentrations were measured and compared to maternal plasma levels. RESULTS Both ANP and BNP were significantly higher in fetal blood compared to the mothers. Fetuses with Rhesus isoimmunisation, characterized by long-term cardiac overload, showed significantly elevated ANP but not BNP concentration compared to the fetal controls (ANP: 80.8+/-16.6 vs. 31.6+/-7.7 pg/ml, P<0.05). However, short-term volume load due to intravascular transfusion leads to a significant increase in the fetal BNP- but not ANP-plasma level (BNP: 112.9+/-14.1 vs. 64.8+/-6.6 pg/ml, P<0.05). CONCLUSION ANP and BNP respond differently to cardiac short- and long-term volume load in the fetal circulation. Therefore, the data suggest that in the fetus, similar to adults, ANP and BNP constitute a dual natriuretic peptide system responsive to changes in cardiac filling pressure.