Ultrastructural and autoradiographic study of preimplantation rabbit embryos grown in conventional or uterine flushing-supplemented culture media.

Rabbit morulae and blastocysts were cultured in conventional culture media [Ham's F10 or BSM II supplemented with bovine serum albumin (BSA) or serum] or in Ham's medium supplemented with synchronous or asynchronous uterine flushings, mostly for 2 days, and afterwards investigated by light and electron microscopy and by autoradiography. Ultrastructure and cell proliferation differed considerably between cultured embryos and noncultured controls. Cultured embryos displayed more dead cells. They were developmentally retarded (predominance of smooth endoplasmic reticulum rather than the age-specific rough endoplasmic reticulum, mitochondria still round to ovoid shaped) and showed nonspecific signs of cells damage (swollen mitochondria and Golgi complex vesicles, increased number of lysosomes). All these features were also present in embryos grown in uterine flushing-supplemented media, but were less pronounced. Cell damage and impaired cell proliferation had affected trophoblast cells more than embryoblast cells. Endoderm could be differentiated only if culture had been started with blastocysts--not with morulae--and seems to require uterine secretions. No significant ultrastructural differences were observed between embryos cultured in synchronous or in asynchronous uterine flushings. Present results indicate that cultured preimplantation rabbit embryos deviate clearly from those grown in vivo and maintain, for some time, a better cellular structure--and probably function--in the presence of uterine flushings than in conventional culture media. Specific abnormal morphologic features related to a particular medium could not be identified.