Lives in the balance: responsiveness of the corpus luteum to uterine and embryonic signals.

This review focuses on factors that may affect the sensitivity of the corpus luteum to uterine prostaglandin F2alpha (PGF2alpha) and embryonic signals. The heterogeneity of the types of cell that are present within the corpus luteum results in complex interactions that ensure complete luteal regression in response to PGF2alpha. There is not likely to be a single factor that determines responsiveness. The sensitivity of the corpus luteum depends on the proper balance of a variety of factors that are involved in mediating the effects of PGF2alpha. This balance is achieved as the early corpus luteum undergoes development, but may also be altered by embryonic factors to rescue the corpus luteum during early pregnancy.