Objective: The presence of GnRH receptors in the human placenta has been re
cognized for a number of years. However, mammalian GnRH, which is expressed
in placental tissues, has limited affinity for the chorionic receptor. On
the basis of immunological and bioactivity data, we have previously propose
d that the chorionic GnRH may differ from mammalian GnRH.
Methods: we have studied the affinity of another isoform of GnRH (ie, salmo
n GnRH and stable analogues of this GnRH isoform), and compared their recep
tor affinity to that of mammalian GnRH and it analogues.
Results: Using our receptor assay method with the labeled mammalian GnRH an
alogue Buserelin, salmon GnRH had a twofold greater affinity for the placen
tal GnRH receptor than did mammalian GnRH and for the stable salmon GnRH an
alogue the affinity was increased tenfold. Using a homologous receptor assa
y method with a stable salmon GnRH analogue as label, the affinity for this
salmon Gn RH analogue had a K-d of 101 nmol/L.
Conclusion: The presence of these higher affinity receptors for non mammali
an GnRH in the human placenta has led us to propose that the chorionic tiss
ues may express more than on iso form of GnRH and that non-mammalian GnRH,
such as salmon GnRH, may be potent regulators of placental functions. (J So
c Gynecol Investig 2001; 8:233-8) Copyright (C) 2001 by the Society of Gyne
cologic Investigation.