FERTILIZATION OF INVITRO GROWN MOUSE OOCYTES

Oocyte-granulosa cell complexes, isolated from 10-d-old mice, were cultured for 10 d in hypoxanthine-supplemented medium. The oocytes increased in size, but the resumption of meiosis was completely suppressed over the culture period. The oocytes were cultured for a further 20 h in an hypoxanthine-free medium, after which germinal vesicle breakdown was observed in 10% of oocytes larger than 60 μ, 53% of oocytes larger than 65 μ and 86% of oocytes larger than 70 μ m in diameter. The oocytes grown and matured in vitro were inseminated with epididymal sperm. When the oocytes were examined 6 h after insemination, 72% of them were undergoing fertilization. Most of the fertilized oocytes had a normal male pronucleus, and the percentage of monospermic oocytes was as high as that obtained for oocytes matured in vivo (87% vs 80%). However, the incidence of abnormality in the female pronucleus of in vitro grown and matured oocytes was much higher than that of oocytes matured in vivo (21 vs 1%). © 1990.