Gonadotropin-releasing hormone, inbibin, and activin in human placenta: Evidence for a common cellular localization

Abstract

The human placenta produces several hypophysiotropic factors that participate in the control of local hormone secretion. In particular, previous reports showed that inhibin and activin modulate both GnRH release and hormonal effect in cultured human placental cells. The present study evaluated the possible correlations among the synthesis and cellular distribution of inhibin, activin, and GnRH in placental villi at term. mRNA coding for inhibin α- and βA-subunits and GnRH were localized in human placenta at term by in situ hybridization using the corresponding cDNA probes. Autoradiograms revealed that some placental cells express inhibin α- and βA-subunit and GnRH mRNAs. A common localization of the three hormonal mRNAs has been found in the inner part of the villi. Using affinity-purified polyclonal antisera, immunocytochemical studies confirmed that in placental villi at term, immunoreactive inhibin α- and βA-subunits and GnRH had a distribution that was superimposable in several areas. Both the outer layer and the inner trophoblasts contained immunoreactive hormonal products. The present data show that some placental cells at term can produce and release inhibin, activin, and/or GnRH. This complement of hypophysiotropic factors may, thus, represent a local paracrine/autocrine control mechanism within the placenta.