LHRH-like immunoreactivity in the human placenta is not identical to LHRH

LHRH-like immunoreactive material was separated from human placental homogenates by chromatography and tested against two antibodies directed respectively against the C- or the N-terminus (N- and C-antibodies) of the synthetic peptide. Extraction yield was 94 per cent as assessed by the recovery of the radiolabelled LHRH added to the homogenates. Placental LHRH-like immunoreactivity in crude extracts appeared largely overestimated, due to interference of endogenous substances non-related to LHRH. After elimination of this contamination, a higher residual activity was detected with the C- than with the N-antibodies. Eluates tested under these conditions contained only 550 pg of LHRH-like material per kg of placenta. This concentration was comparable whether placental tissue had been sampled at 12 weeks of pregnancy or at the end of gestation. The corresponding peptides however neither co-eluted with synthetic LHRH nor with catabolite fragments of the peptide. It is concluded that the human placenta contains a lesser amount of LHRH-like material than anticipated on the basis of earlier results and that this material does not correspond to the native decapeptide.