The two to four-cell embryos as source tissue of the tetrapeptide preventing ovulations in the hamster

A tetrapeptide compound, derived from oviductal contents at 40 hours post-coitus, prevents ovulation when injected subcutaneously into cyclic hamsters (Kent, '73). The present experiments were designed to determine whether the source of the tetrapeptide is from the ova, embryos, oviducts or semen. Oviducts were either untouched or ligated at the ovarian or uterine end to limit contents to embryos, semen or ova and the contents then recovered at 40 hours pc and injected into cyclic hamsters. The results indicate that the source of the tetrapeptide is the embryos.