Influences of prolactin upon spermatogenesis and spermatozoa during in vitro fertilization in mice

Hyperprolactinemia, induced by pituitary isografts for 20 weeks in male mice and confirmed by radioimmunoassay using anti-mouse prolactin serum, did not impair spermatogenesis in the testis and maturing processes of spermatozoa in the epididymis. Incubation of freshly obtained epididymal spermatozoa for 90 min in culture media containing various levels of mouse prolactin did not yield any adverse effects on percentage motility rates of epididymal spermatozoa. When the level of mouse prolactin in the preincubation medium for epididymal spermatozoa was 100 ng/ml, the rate of fertilization by these preincubated spermatozoa in the subsequent in vitro fertilization experiment was significantly lowered compared with that observed in controls. However, when the level of prolactin in preincubation media was 10 ng/ml, no significant reduction in the rate of fertilization occurred. The present experiments seem to indicate the existence of some differences in the effects of prolactin on male germ cells until they reach the tail of the epididymis and on the processes of capacitation and/or fertilization by epididymal spermatozoa after they leave the epididymis.