Capacitation seems to be under hormonal control being inhibited by proges- terone and requiring estrogen stimulation (4). The inhibition of this process by progesterone was found only in the uterus. In the fallopian tubes proges- terone failed to influence the capacitation of the spermatozoon.

lmmunoreactive prolactin in high concentration was detected in the human semen. Therefore, the effect of prolactin on the various metabolic parameters of the human spermatozoa was studied. It was found that prolactin brought about many of the biochemical changes in the spermatozoa which are known to be associated with the process of capacitation. These results suggest that prolactin has a role in the sperm capacitation.