Atrial natriuretic factor production by the human placenta.

Atrial natriuretic factor (ANF), a 28 amino acid peptide, is primarily produced and secreted by cardiac atrial myocytes to modulate cardiovascular and renal functions. Although ANF is also produced in tissues other than the heart, it remains uncertain whether the peptide is synthesised by human placentae. We provide here evidence from in vitro studies suggesting de novo production of ANF by the human placenta. Placental tissues were collected from normal term pregnancies by elective Cesarean section and acid extracted for ANF radioimmunoassay. The level of placental immunoreactive (ir) ANF was 186 +/- 33 pg/gm wet tissues (mean +/- SE, n = 6). Perfusates from in vitro perfusion of the fetoplacental compartment of placental lobules yielded 26 +/- 6 pg/min/gm wet tissue (n = 3) of irANF. Furthermore, pro-ANF mRNA signals were localised by colorimetric in situ hybridization in a subpopulation of placental cytotrophoblast-like cells, but not in syncytiotrophoblasts nor in chorionic cells of placental sections. Northern blot analysis of placental tissue extracts showed a single band of pro-ANF mRNA signals (-0.85 Kb) similar in size to that found in the rat heart. Our findings suggest that ANF is expressed and produced by a small population of human placental cytotrophoblast-like cells. The possibility that placental ANF may be secreted locally or into the fetoplacental circulation to exert paracrine, autocrine or both effects now needs to be considered.