The similarity of chorionic gonadotrophin and its subunits in term placentae from man, apes, old and New World monkeys and a prosimian.

Chorionic gonadotrophin (CG) was estimated, by bioassay and radioimmunoassay (RIA), in placental extracts from 11 ape and monkey species. There was a significant correlation between the results of the two assay systems (r = 0.903, p less than 0.001). The concentration of CG in most primate term placentae was the same as that in the human placenta at term. Extracts from all placentae cross-reacted with antiserum to ovine LH-beta subunit, and those of the chimpanzee and gorilla also had a significant cross-reaction with an antiserum to the carboxyl terminal peptide of the HCG-beta subunit. Primate placentae chromatographed on Sephadex G-200 had components active in the RIA systems for HCG, HCG-alpha HCG-beta subunits. In general, the elution profiles of all ape and monkey placental extracts resemble those made from human term placentae and of purified HCG and its subunits. The shape of the elution patterns from human and non-human material suggests that there was more than one molecular form of CG-alpha subunit activity. A second, more retarded molecular form having beta subunit activity was found in extracts made from human, gorilla, gibbon and rhesus monkey placentae. The similarity between the structure of ape and monkey placental CG with HCG and its subunits implies a function similar to that of HCG in late pregnancy.