Action of chicken II GnRH on the human placenta.

The stability, receptor binding, bioactivity, and production of chicken II GnRH and its analogs in the human placenta were studied. Both chicken II and mammalian GnRH are rapidly degraded by placental enzymes, yet the chicken II isoform is six times more stable. Analogs of chicken II GnRH were synthesized, and their stability in the presence of placental enzymes was tested. The d-Arg(6)-chicken II GnRH-aza-Gly(10)-NH2 analog was found to be resistant to enzymatic degradation. The placental receptor binding activity of the chicken II GnRH analogs and chicken II GnRH was compared with that of mammalian GnRH and its analogs. Because d-Arg(6)-chicken II GnRH-aza-Gly(10)-NH2 had the highest affinity for the placental receptor and was stable in placental extracts, the bioactivity of this analog on the regulation of placental human CG (hCG) release was compared with that for mammalian and chicken II GnRH using a human term placental explant culture system. This chicken II GnRH analog effected a stimulation of hC...