Influence of the mucin coat on the survival of rabbit and mouse embryos stored at 0 degrees C.

To examine the factors affecting the survival of refrigerated embryos, rabbit and mouse morulae were stored at 0 degrees C in modified phosphate-buffered saline (PB1) or in PB1 containing 0.75 M sucrose. Survival was defined as the ability to develop into an expanded blastocyst in culture. The data was analyzed with special reference to the presence of a mucin coat around the embryos. When rabbit morulae were stored in isotonic PB1 for 2, 4, 6, and 8 days, survival rates were 98%, 88%, 85%, and 50%, respectively. However, if the mucin coat had been removed before storage, the rates were lower (95%, 75%, 36%, and 3%, respectively). Sucrose impaired the survival of rabbit morulae irrespective of the presence of the mucin coat. Only 11% of mouse morulae survived 2 days of storage in PB1 medium, but if the medium contained sucrose, survival rates after storage for 2, 3, 4, and 5 days were higher (83%, 55%, 31%, and 7%, respectively). To provide them with a mucin coat around the zona pellucida, mouse embryos were incubated in a rabbit oviduct. Survival rates of these embryos after storage in the presence of sucrose did not decrease over 4 days of refrigeration (98-92%), and the rates after storage for 5, 6, and 7 days were 65%, 40%, and 30%, respectively; embryos that had been stored for 5 days were transferred to recipient mice, and live young were born. Agar embedding of mouse morulae did not have the same effect as the mucin coat.(ABSTRACT TRUNCATED AT 250 WORDS)