Gonadotrophin in the term placenta of the dolphin (Tursiops truncatus), the Californian sea lion (Zalophus californianus), the grey seal (Halichoerus grypus) and man

: Chorionic gonadotrophin activity in extracts of the term placenta of a dolphin, a sea lion and a grey seal was measured by its effectiveness in increasing uterine weight in the mouse and by solid-phase RIA using hCG as immunogen and labelled antigen. Bioreactive (B) gonadotrophin was found in these placentae and, compared to the human term placenta, the concentration of CG in the dolphin was higher, in the sea lion similar and in the grey seal lower. The biological activity in each species was neutralized with a rabbit anti-hCG serum. All placental extracts contained material active in the hCG immunoassay (I). The ratio B/I was significantly higher for the CG in the placental extracts of the marine mammals compared with that of the human term placenta. Results of in-vivo bioassay, RIA, electrophoretic and gel-chromatographic studies indicate structural similarities between CG in the placentae of the marine mammals and human CG.