Luteotropic effects of bovine blastocysts

A series of experiments was conducted to determine whether 18-day bovine blastocysts could stimulate synthesis of progesterone by dispersed bovine luteal cells in vitro. Both blastocyst homogenates and extracts of blastocyst homogenates were luteotropic. The luteotropic activity of the blastocysts appeared to be due to one or more heat-labile substances with a molecular weight of less than 12,000 daltons.