Effects of prolactin during preincubation of mouse spermatozoa on fertilizing capacity in vitro.

In the present study, some beneficial effects of mouse prolactin (PRL) on spermatozoa were demonstrated in mice. The motility rate of spermatozoa is well maintained during incubation in modified Krebs-Ringer bicarbonate solution (mKRB) containing PRL (10 or 100 ng/ml) for up to 120 min. When spermatozoa that had been preincubated in the same PRL-containing mKRB were incubated with oocytes in mKRB, significantly more spermatozoa attached to the zona pellucida of each oocyte. When spermatozoa that had been preincubated in mKRB with PRL (50 and 100 ng/ml) for only 15 or 30 min were used for in vitro fertilization (IVF), significantly higher fertilization rates were yielded by those spermatozoa than by control spermatozoa preincubated without PRL for the same periods. The prolongation of the preincubation period did not result in increased fertilization rates. Thus, PRL demonstrated biological effects on spermatozoa by shortening the optimal preincubation period for spermatozoa to acquire capacitation and by maintaining their motility and ability of the attachment to the oocyte during IVF. The results are relevant to clinical application of PRL for infertile patients with oligozoospermia or asthenozoospermia.