高濃度で前培養された射出精子による豚卵子の体外受精

抄録

Sperm rich portions of fresh boar ejaculates were washed twice and preincubated in a modified Krebs-Ringer bicarbonate solution (Toyoda et al., 1971) at different concentrations for various periods at 37°C under 5% CO₂ in air. The preincubated spermatozoa were then added to pig eggs matured either in vivo or in vitro. Final sperm concentration at insemination was adjusted to 5 × 10⁵ cells/ml in each experiment.
The rate of penetrated eggs, as examined at 20 h after insemination, was markedly increased with elevated sperm concentrations during preincubation and with the increased preincubation periods, reaching 83-100% with spermatozoa preincubated at a concentration of 40 × 10⁸ cells/ml for 4 h. These spermatozoa showed vigorous, hyperactivated movement when diluted in fertilization medium.
Penetrated eggs at stages of anaphase to telophase of second meiosis were frequently observed at 4 h and female pronucleus was observed at 6 h after insemination. While in vitro matured eggs did not develop further due to failure in male pronucleus formation, in vivo matured eggs reached the 2-cell to 8-cell stage after 48 h in culture.
These results demonstrated the possibility of in vitro capacitation of boar ejaculated spermatozoa in a defined medium and suggested that sperm concentration during preincubation is important to capaci-tate spermatozoa.