Interaction of semen with ova in vitro.

Spermine had a beneficial effect on the fertilization of zona-free mouse ova in vitro. A deleterious effect of spermine or seminal plasma on gametes only occurred if normal, untreated BSA was present in the incubation medium. This was due to the activity of spermine oxidase, which could be assayed in the untreated BSA and which was removed by TCA-purification of the BSA. The addition of a spermine oxidase inhibitor, isoniazid, or the use of the TCA-purified BSA preparation allowed the direct effects of spermine or seminal plasma on mammalian fertilization to be assessed. Human seminal plasma retarded the acquisition of fertilizing ability in human spermatozoa and prevented it in mouse spermatozoa. The fertilizing ability of the spermatozoa of both species was unaffected, when spermatozoa were preincubated to achieve capacitation before adding the seminal plasma.