Abstract
The inhibitory effect of boar seminal plasma (BSP) and its fractions (BSP Fr-1 and BSP Fr-2) on the fertilization was investigated by using the mice eggs. The superovulated oocytes and epididymal spermatozoa from mature mice of ICL:ICR strain were used for fertilization. The medium used for sperm preincubation and fertilization was a chemically defined medium according to TOYODA et al. (1971).
BSP was obtained by centrifugation of semen which had been collected from fertile boars by hand globed method. BSP Fr-1 and Fr-2 were prepared by gel-filtration of BSP using Sephacryl S-200. Either BSP or BSP Fr was added to the medium for sperm preincubation and/or fertiliza-tion. Eggs were examined 4-5 h after the insemination.
When 1 or 10% BSP was present in the medium, fertilization was completely inhibited both in the ova with and without cummulus cells. Although the presence of BSP in medium did not affect adversely the motility of mouse spermatozoa, those motile spermatozoa coud not penetrate the zona pellucida. The dispersal of cummulus cells were inhibited when 10% BSP was present in the medium for fertilization. When concentrated BSP Fr-1 (2.3 mg protein/ml) was added 10% of medium for fertilization, sperm penetration was completely inhibited, while the similar addition of concentrated BSP Fr-2 (18.4 mg protein/ml) the inhibition was approximately 60%.
These results demonstrate that BSP inhibits distinctly the fertilization of mouse eggs by mouse spermatozoa in vitro without impairing motility and viabilty of the spermatozoa. It is considered that the inhibitory factor in BSP Fr-1 might correspond to a macromolecular fraction which is known as decapacitation factor or sperm coating antigen.
