AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 3 633-R638, Copyright © 1991 by American Physiological Society
Heterogeneous binding sites for alpha-atrial natriuretic peptide in human umbilical cord and placenta
S. P. Salas, R. F. Power, A. Singleton, J. Wharton, J. M. Polak and J. Brown
Royal Postgraduate Medical School, London, United Kingdom.
The distributions of atrial natriuretic peptide (ANP) clearance receptors
in human umbilical cord and placenta were investigated by using
des[Gln18,Ser19,Gly20,Leu21,Gly22]ANP-(4-2 3) (C-ANP) as a specific ligand
of this receptor to displace bound alpha-125I-labeled ANP. alpha-125I-ANP
bound reversibly to umbilical venous and arterial intima and to fetal
placental and maternal decidual tissues, with dissociation constants of
1.24 +/- 0.51, 0.58 +/- 0.19, 1.86 +/- 0.51, and 1.07 +/- 0.25 mM,
respectively. Binding was reversed by 1 microM unlabeled alpha-ANP but not
by unrelated peptides such as gastrin. The 1 microM C-ANP displaced bound
alpha-125I-ANP from the intima of umbilical artery but not that of the
vein. The specific reversible binding of alpha-125I-ANP to placental
decidua but not to fetal placenta was also displaced by 1 microM C-ANP.
Therefore high-affinity binding sites for alpha-ANP on the intima of the
umbilical artery and on placental decidua differ from those on the
umbilical vein and on fetal placental tissue; the binding sites of the
intima of the umbilical artery and of the decidua in humans are consistent
with clearance receptors for alpha-ANP.
