Atrial natriuretic peptide receptors in normal human placentas.

We studied whether plasma membranes from normal human placentas contain receptors for atrial natriuretic peptide. We identified specific, high-affinity, low-capacity atrial natriuretic peptide binding sites in the nonbrush border, microsomal fraction presumed to originate from cellular membranes near the fetal circulation. In contrast, no atrial natriuretic peptide binding sites could be identified in the brush border; the latter is exposed to maternal blood in the intervillous space. The presence of atrial natriuretic peptide binding sites in human placentas suggests that atrial natriuretic peptide may be involved in fluid and electrolyte homeostasis in human gestation.