Effects of prolactin on gametes and zygotes during in vitro fertilization in mice

Hyperprolactinemia is one of the major causative factors of infertility. However, the effect of prolactin on gametes during in vitro fertilization has not been elucidated. In the present study, the effects of mouse prolactin on the motility of spermatozoa, in vitro fertilization, and in vitro development of the zygote were investigated in mice using media containing three different concentrations (10, 50, and 100 ng/ml) of mouse prolactin. The development of unfertilized and fertilized oocytes (zygotes) was not affected in vitro by prolactin regardless of the amount of prolactin added to culture media. However, the fertilizing capacity of the spermatozoa was suppressed when they were preincubated for 90 min in culture media containing prolactin at concentrations of 50 and 100 ng/ml. The motility of spermatozoa was not affected by prolactin regardless of the concentration of prolactin used for preincubation. The present study indicates that prolactin may have some effects on the capacitation process of spermatozoa in vitro. This result should be taken into consideration in in vitro fertilization and embryo transfer procedures in humans.