Chorionic gonadotrophin secretion by human blastocysts.

Abnormal embryos that arose in our in-vitro fertilization programme were cultured in serum-free minimum essential medium (MEM), and those that developed into blastocysts were cultured up to day 14 after fertilization to study the influence of various supplements on chorionic gonadotrophin (CG) secretion. Human cord serum, at a concentration of 1%, was found to be one of the most effective stimulants for initiating and maintaining CG production. A mixture of insulin+transferrin+selenium (ITS) stimulated CG secretion in serum-free MEM, although the output of hormone began to decline after approximately 3 days. Platelet-derived growth factor (PDGF) produced a similar response to ITS. Stimulation of blastocyst CG secretion in the absence of serum could also be induced with 8-bromo-cAMP. All stimulants were able to evoke CG secretion in day 7-8 blastocysts. These studies have shown that multiple factors were capable of inducing CG production by early blastocysts. On the basis of these and other studies it was postulated that receptors for insulin, transferrin and PDGF were expressed in preimplantation blastocysts.